Evaluation of the primary skin irritation and allergic contact sensitization potential of transdermal triprolidine

FUNDAMENTALANDAPPLIEDTOXICOLOGY

17,103-119(1991)

Evaluation of the Primary Skin Irritation and Allergic Contact Sensitization Potential of Transdermal Triprolidine MICHAEL K. ROBINSON,*

*He&l

KATHLEEN W. PARSELL,* DEBRA L. BRENEMAN,~ AND CHARLES A. CRUZE*

und Peuonal Care Technology Division. Procter & Gamble Company, Miami Valley Laboratories, Cincinnati. Ohio 45-739-8707: and TDepartment of‘ Dermatology, University of Cincinnati Medicul Center, Cincinnati, Ohio 45221

Received September 21, 1990: arcepted January 4. 1991

Evaluationof thePrimarySkinIrritationand Allergic Contact Sensitization Potential of TransdermalTriprolidine. ROBINSON, M. K.. PARSELL. K. ~.,BRENEMAN, D. L., ANDCRUZE.C. A. (1991). Amdam. Appl. To.xicol. 17, 103-l 19. A transderrnal patch for the OTC antihistamine, triprolidine (TP). might provide benefits in terms of increased efficacy and reduced sedative side effects. However, concerns over potential irritant or allergic contact sensitization (ACS) skin reactions necessitated thorough skin toxicity testing before and during initial clinical development. Initial effort was expended on development of a binary vehicle delivery system comprised of TP in 0.5% oleic acid (OA) in propylene glycol (PG). Rabbit skin irritation and Buehler guinea pig skin sensitization testing indicated that this TP/OA/PG formula had both skin irritation and ACS potential. Both tests underestimated, to some degree, the skin toxicities observed in later clinical testing. In clinical tests, skin irritation was due mainly to the OA/PG vehicle. but was enhanced in the presence of high TP concentrations. Of 26 subjects enrolled in a rising dose clinical pharmacokinetics study, one subject exposed twice to TP/OA/PG presented with delayed skin reactions suggestive of ACS. Positive diagnostic patch test results for this subject and four out of five other twice-exposed study subjects suggested that the TP/OA/PG formula had a very high ACS potential. Subsequent predictive clinical patch testing was conducted with a buffered aqueous TP formula whichprovidedin vitro skinpenetration of thedrugequivalent to theTP/OA/PGformula.These clinical studies demonstrated that TP itself had no significant irritation potential but still induced ACS reactions in a high proportion of test subjects. The incidence of adverse skin reactions to TP was considered to be too high relative to the degree of improved therapeutic benefit of this delivery form. On this basis, all technology development effort was discontinued. Q 1991 Society of Toxicology

The delivery of drugs via the transdermal route has become increasingly utilized as an alternative delivery mechanism for established drugs. The rationale is that transdermal delivery systems(TDS)’ offer the potential advantagesof providing controlled releaseof a drug for specified periods and avoiding hepatic first ’ Abbreviations used: ACS. allergic contact sensitization; ETOH. ethanol: HRIPT, human repeat insult patch test: OA. oleic acid: PG. propylene glycol; PII, primary irritation index: PK. pharmacokinetics: SLS, sodium lauryl sulfate: TDS. transdermal delivery system: TP. triprolidine. 103

passmetabolism (Guy et al., 1987; Chien and Banga, 1989). This eliminates the peaks and troughs associatedwith oral or parenteral administration. Though systemicsideeffectsmay be associated with transdermal applications, these effects are generally milder and better tolerated (Holdiness, 1989). From an efficacy/systemic side effect viewpoint, the OTC antihistamine triprolidine (TP) is an attractive candidate for transdermal delivery. Due to a relatively short half-life (Simons et al., 1986) and high potency, the rel0272-0590/91

$3.00

Copyright is’ 199 I by the Sowty of ~loxxology. \II rights of reproduction m any form reserwd

104

ROBINSON

atively low approved oral dose of TP must be taken several times a day. Resulting plasma levels are variable (Simons et al., 1986). The sedative side effects of antihistamines may be associated with high peak plasma concentrations (Peck et al., 1975; Carruthers et al., 1978) which might be avoided by controlled transdermal delivery. While systemic side effects of drugs may be reduced or eliminated by transdermal delivery, the delivery of drugs through the skin introduces a new aspect of potential skin toxicity that must be addressed. Every major TDS marketed to date has encountered some degree of allergic or irritant skin reactivity, or both, due either to the active drug or to another patch system component(s) (Holdiness, 1989; Hogan and Maibach, 1990). Some allergic manifestations have become apparent only after widespread clinical use (Holdiness, 1989; Maibach, 1985) and were not predicted by prior animal or human sensitization testing (Maibach, 1985; Goeptar et al., 1988). As a class, the antihistamines are regarded as significant contact allergens when applied topically (Fisher, 1986b). Allergic reactions to certain antihistamines can result from crossreactivity to nitrogen-linked ethylenediaminerelated antihistamines in patients sensitized to the stabilizer, ethylenediamine (Balato et al., 1984). Allergic contact sensitization (ACS) reactions have also been reported in patients treated with topical antihistamines such as promethazine, diphenhydramine, and chlorpheniramine (Sidi et al., 1955; Vickers, 1961; Tosti et al., 1990). TP is in a different chemical class (propylamine antihistamines) from those antihistamines more commonly associated with adverse skin reactions (ethanolamine and phenothiazine antihistamines) (Fisher, 1986b) and thus may have lower ACS potential. There have been no literature reports of allergic skin reactions to TP. However, this may only be due to the fact that a topical dosage form has not yet been marketed (Fisher, 1986b). As part of our technology development effort around a transdermal TP delivery system, we conducted a thorough evaluation of the

ET AL.

skin irritation and sensitization potentials of TP and vehicle components. Initial efforts were focused on a binary solvent delivery system comprised of 0.5% oleic acid (OA) in propylene glycol (PG). Though effective in delivering TP through the skin both in vitro (G. L. Manring, unpublished results; G. B. Kasting et al., manuscript submitted for publication) and in vivo (R. W. D’Souza et al., manuscript in preparation), significant adverse skin reactions (both primary skin irritation and ACS) precluded further development of the OA/PGbased formula. A buffered (pH 7.0) aqueous TP formula was subsequently developed which provided TP delivery in vitro that was comparable to the OA/PG vehicle system (G. B. Kasting et al., manuscript submitted for publication). Though it was nonirritating, sensitization testing of this aqueous formula provided the first definitive evidence of the ACS potential of the active drug itself. This report summarizes all of these data, their impact on the development of a transdermal delivery formulation for triprolidine, and the implications for transdermal delivery of antihistamines and other drugs. MATERIALS

AND METHODS

.4nimals. Hartley albino guinea pigs (Harlan SpragueDawley, Inc., Indianapolis, IN) were used for preclinical skin sensitization testing. New Zealand albino rabbits (Mohican Valley Rabbitry, Loudonville, OH) were used for preclinical primary skin irritation testing. All animals were acclimated for 7 days prior to study, were singly housed, and were provided food and water ad libitum. Test materials. Test materials included triprolidine hydrochloride (tram-2[3-( l-pyrrolidinyl)-l-p-tolylpropenyllpyridine, 99.75% purity) from H. Reisman Corp. (Orange, NJ). oleic acid (cis-9-octadecenoic acid) from Nucheck Labs (Elysian, MN), propylene glycol (1.2-propanediol) from Fisher Scientific (Fair Lawn, NJ), and sodium lauryl sulfate from Fisher Scientific. Guinea pig skin sensitization test. A modification of the Buehler method (Ritz and Buehler, 1980: Robinson et al.. 1990) was used for induction and elicitation of contact sensitization in the guinea pig. The studies were conducted at Springbom Life Sciences (Spencerville, OH). The animals received three or nine 6-hr induction exposures of test materials at the same shaved site by occluded patch, once or three times a week for 3 weeks. Ten to 13 days

TRIPROLIDINE

SKIN

IRRITATION

after the last induction exposure, the animals were challenged at shaved naive skin sites by a 6-hr occluded patch exposure to the test material. The sites were graded 24 and 48 hr after the challenge patches were removed according to a five-point grading scale (Ritz and Buehler, 1980; Robinson eta/., 1990). Erythema scores of > I were considered positive responses. The relative incidence and severity of “positive” reactions among the test and control animals were used as a basis for interpreting the test results (Ritz and Buehler. 1980; Robinson et al., 1990). Rechallenge of the same test animals (and new, previously unexposed control animals) was conducted 7 to 14 days after challenge. Study-to-study consistency in conduct of the test protocol and application of skin grading criteria was verified through established monitoring procedures. Rabbit primary skin irritation test. Closed-patch rabbit irritation tests (McCreesh and Steinberg, 1987) were conducted at Springborn Life Sciences (Spencerville. OH). Three rabbits were exposed for 4 hr and three rabbits were exposed for 24 hr to the test materials at preshaven test sites under occluded patches. The patches were secured with dental dam and elastic tape. Approximately 30 min after patch removal, the patch sites were graded for erythema/eschar and edema (McCreesh and Steinberg, 1987). Grading was repeated 24 and 48 hr after patch removal. The overall grades were calculated by averaging the grades from the three observation periods for all animals in a treatment group for erythema/eschar formation (nine grades) and separately for edema formation (nine grades). To calculate the primary irritation index (PII), the two average grades (erythema/eschar and edema) were then added. Skin grades observed after the 4 and 24-hr exposure periods were recorded separately. Humun skin irritation testing. Human skin irritation testing was done by occluded patch methods and was conducted either through Hilltop Research (Cincinnati. OH) or the New Drug Evaluation Unit and the Department of Dermatology, University of Cincinnati, School of Medicine (Cincinnati, OH). All human test protocols were reviewed by the appropriate institutional review board and all test procedures thoroughly reviewed with all test subjects (and informed consent obtained) prior to initiation of the studies. The Hilltop Research studies included 24,48. or repeat 24-hr exposure (3 and 21 day) patch tests. The studies were conducted with males or females by applying one or more patches to the upper outer arms of the test subjects and leaving them in place for the appropriate test durations. The patches were then removed at the test facility and the skin sites graded according to the following irritation grading scale: O-No evidence of irritation. 1 -Faint but definite erythema. no eruptions or broken skin or no erythema but definite dryness: may have epidermal fissuring. 2-Moderate erythema. may have a few papules or deep lissures, moderate-to-severe erythema in the cracks.

AND

SENSITIZATION

105

3-Severe erythema (beet redness), may have generalized papules or moderate-to-severe erythema with slight edema (edges well defined by raising). 4--Generalized vesicles or eschar formations or moderate-to-severe erythema and/or edema extending beyond the area of the patch. Half grades (i.e., 0.5, 1.5. 2.5, and 3.5) were assigned if reactions fell between the unit grades. Grading was repeated according to various time schedules as noted in the tables and figures. Irritation testing at the University of Cincinnati New Drug Evaluation Unit was conducted concurrently with pharmacokinetics evaluations in male test subjects. The patches (prototype transdermal patches) were applied to the upper back and remained in place for approximately 24 hr. The patch sites were graded for irritation (at the timepoints indicated in the tables) according to the above scale. Human diugnostic patch testing for contact sensitization. Twenty-four or 48hr exposure diagnostic patch tests were conducted under the general guidelines of the International Contact Dermatitis Research Group and the North American Contact Dermatitis Group (Fregert. 1981: Fisher, 1986a). Patches were applied to the upper back under occlusive tape. The patch sites were graded at the indicated time points using the following grading scale (Fregert, 1981): ?, Doubtful reaction, faint erythema only +, Weak positive reaction; erythema. infiltration, possibly papules ++, Strong positive reaction: erythema. infiltration, papules, vesicles +++, Extreme positive reaction; intense erythema and infiltration and coalescing vesicles -, Negative reaction IR. Irritant reaction of different types NT, Not tested According to this scale, “+” reactions are considered indicative of an allergic reaction provided they are of a persistent and reproducible nature and similar reactions are not observed in control (naive) individuals. In one diagnostic patch test study, the human repeat insult patch test (HRIPT) grading scale of Stotts was used (Stotts. 1980). This HRIPT method was used for the diagnostic patch test phase of a 21-day cumulative irritation patch test (Phillips et al.. 1972; Maibach, 1986) due to the fact that the induction exposure regimen was similar to standard HRIPT test methodology (Stotts, 1980; Robinson et al.. 1989). Human open application skin test. A repeat open application skin test was conducted among those subjects who demonstrated evidence of ACS reactions to TP during cumulative irritation patch test exposures. Test subjects were instructed to apply 25 ~1 of test material and vehicle alone to the antecubital fossae of separate arms. These materials were rubbed into the site by the test subjects using a glass rod. This procedure was repeated twice daily

106

ROBINSON

ET AL.

TABLE I RABBIT

IRRITATION

PATCH

TESTING

OF TRIPROLIDINE/~LEIC

ACID/PROPYLENE

GLYCOL~

Resultsb Material

Vehicle

Propylene glycol

Water Water

Concentration (o/o) 80

Oleic acid

Propylene glycol

Triprolidine

Propylene glycol

Triprolidine

1% Oleic acid in propylene ?Avcol

90 100 0.75 I.0 2.0 12 24 12 24

4

hr PII 0.3 0.3 0.3 0.2 0.3 0.4 0.3 0.4 0.9 0.6

24

hr PII 0.7 0.7 0.9 1.0 I.0 1.3 0.8 0.8 2.4 2.8

a Study conducted with three test animals for the 4-hr exposure and three test animals for the 24 hr exposure (see Materials and Methods). ’ Results expressed as primary irritation index (PII) (McCreesh and Steinberg, 1987).

for up to 2 weeks (unless terminated early due to skin reactivity). Skin grading was conducted once a week, and more frequently if the subjects reported a skin reaction. Subjects were instructed to notify the test facility in the event of an adverse skin reaction so that additional skin grading could be arranged. Skin grading was done according to the HRIPT grading scale (Stotts. 1980). Although different protocols and grading scales were used for the various clinical irritation and sensitization test procedures, there was a high degree of consistency maintained in applying specific grading criteria and in overall interpretation of skin reaction grades. This was achieved through use of well-established testing facilities, blinded protocols, and the independent evaluation of skin reactions, across most studies, by individuals with extensive experience and expertise in clinical skin testing methods. This included individuals with no direct involvement in the overall drug development effort. .4dverse reactions. Adverse reactions in the clinical tests were limited to skin irritation and ACS. Although systemic reactivity to oral drugs is rare in subjects cutaneously sensitized to those drugs (Maibach, 1987) all such subjects were warned of possible systemic reactions to oral triprohdine. These subjects were advised not to take TPcontaining medications unless under medical supervision.

RESULTS Primary

skin irritation

conducted preclinical

testing. We first

testing of the primary

irritation potential of TP as well as the vehicle components (OA and PG) in rabbits. Both OA and PG showed minimal irritation (PI1 < 2) after 4 or 24 hr of exposure (Table 1). Triprolidine also showed minimal irritation out of a simple propylene glycol vehicle. However, the irritation increased to a moderate level (PI1 > 2, after 24 hr patch exposure) when the full formulation (12 or 24% TP/ 1% OA/PG) was tested. Human irritation testing of the vehicle components only was conducted using 24- and 48-hr occluded patch testing procedures (Table 2). In the 24-hr patch test, saline, 0.075-I .O% sodium lauryl sulfate (irritant control), and propylene glycol were graded as very mild to mild (average skin grades < 1.O on O-4 scale) at both 30 min and 24 hr (post patch removal) grading time points. The strongest skin reactions observed (1.5 on O-4 scale) were considered only mildly irritating. The average skin reaction to OS-3.0% OA in PG was also mild ( -=c1.5 on O-4 scale); however, among individual test subjects, reactions ranged from negative (0) to moderately (32) or severely (93) irritating, particularly at oleic acid concentra-

TRIPROLIDINE

SKIN

IRRITATION TABLE

AND

107

SENSITIZATION

2

HUMAN IRRITATION PATCH TESTING OF OLEIC ACID/PROPYLENE GLYCOL VEHICLE COMPONENTS Human (24-hr patch)-16

subjects Results” Average

Material

Concentration (%)

Saline Sodium lauryl sulfate

100 0.075 0.1 100 0.5 1 2 3

Propylene glycol Oleic acid

Human (48-hr patch)-16

Range

Vehicle

30 min

24 hr

30 min

24 hr

-

0.16 0.09 0.15 0.50 0.93 1.06 0.84 1.06

0 0.44 0.50 0.34 0.87 1.06 1.12 1.21

O-l.5 O-l.0 O-I.0 o-1.5 O-2.0 0.5-2.0 0.5-1.5 0.5-2.0

o-o O-I.0 O-l.5 O-1.0 O-l.5 O-3.0 0.5-3.0 0.5-3.0

Water Water

Propylene glycol

subjects Results” Average

Material

Concentration (%)

Saline Sodium lauryl sulfate Propylene glYCO1 Oleic acid

100 0.075 0.1 100 0.5

Range

Vehicle

30 min

24 hr

48 hr

30 min

24 hr

48 hr

-

0.27 0.55 0.40 0.27

0.14 0.68 0.80 0.45

0.05 0.45 0.60 0.36

o-o.5 O-l.0 O-l.0 o-o.5

o-o.5 O-l.0 0.5-1.5 O-l.0

o-o.5 o-o.5 0.5-1.0 O-l.0

Propylene glycol

0.57

0.74

0.67

O-2.5

O-2.5

O-2.0

Water Water

’ Results are expressed at the average (mean) irritation grade for all test subjects as a function of time after patch removal, and the range (minimum-maximum) of individual subjects’ grades. See Materials and Methods for grading scale and descriptive terminology.

tions above 0.5%. Reactions in the 48-hr patch in preparation). With the exception of one test were only slightly more severe at equiva- testing cycle (seebelow), subjectswere exposed lent test concentrations (note that only the to the formulation only once. In all cases,the 0.5% oleic acid concentration was tested in delivery vehicle consistedof 0.5% OA with PG the 48-hr test). comprising the balance. Separatesubjectswore The primary human skin irritation potential placebo (OA/PG only) patches. Patches were of the full TP/OA/PG transdermal formula- removed after the 24-hr exposure period and tion was evaluated in the context of a phar- the skin sites were graded for irritation at 2, macokinetics (PK) study conducted in a rising 24, and 48 hr post patch removal. The skin dose(TP dose)fashion. Subjects were initially irritation gradesare shown in Table 3. exposed (24-hr occluded patch) to 1% TP and The average skin irritation grades due to in later cycles to single patches at 5% TP, du- the OA/PG vehicle itself were in the range of plicate patches at 5% TP, and single patches 0.72-1.75, consistent with prior human irriat 15% TP (R. W. D’Souza et al., manuscript tation patch test results (see also Table 2).

108

ROBINSON

ET AL.

TABLE 3 CLINICAL IRRITATION TEST RESULTS FROM 24-hr PATCH EXPOSURE IN PHARMACOKINETICS STUDY Results” Average

Range

Subjects

Material

Concn (%)

Vehicle

2 hr

24 hr

48 hr

2 hr

24 hr

48 hr

4

Triprolidine

1

1.75

1.625

1.125

1.0-2.5

0.5-2.5

0.5-1.5

2

Oleic acid

0.5

1.5

1.75

1.5

1.o-2.0

0.5-3.0

0.5-2.5

16

Triprohdine

5

1.07

1.11

0.75

0.5-2.5

0.5-2.0

0.5-1.5

8

Oleic acid

0.5

0.97

0.91

0.72

O-2.0

0.5-3.0

0.5-2.5

6

Triprolidine

0.5% Oleic acid in propylene glycol Propylene glycol 0.5% Oleic acid in propylene glYCOl Propylene glycol 0.5% Oleic acid in propylene glycol

2.15

2.25

1.08

1.o-4.0

0.5-4.0

0.5-1.5

15

a Results are expressed as the average (mean) irritation grade for all test subjects as a function of time after patch removal, and the range (minimum-maximum) of individual subjects’ grades. See Materials and Methods for grading scale and descriptive terminology.

Again, individual subject irritation reactions ranged as high as 3.0 (severely irritating). Incorporation of TP into the formula at concentrations of 1 or 5% had no effect on the irritation response suggesting that it was strictly due to the OA/PG vehicle. Incorporation of TP into the formula at 15% produced an entirely different pattern of response. Here the average irritation grade increased to >2.0 (moderately irritating) at the 2- and 24-hr post patch removal timepoints. Moreover, there was considerable intersubject variability in response. As shown in Table 4, three of the six test subjects presented with extreme irritation reactions (grade 4) whereas the other three subjects showed reactions more typical of the vehicle alone. These severe reactions had largely dissipated by 48 hr after patch removal. Interestingly, there was a direct correlation between the skin irritation reactions observed in these six subjects and the subsequently measured plasma levels of TP (R. W. D’Souza, manuscript in preparation).

Because of the kinetics of appearance and decline of the three severe skin reactions shown in Table 4, it was determined that these likely represented only irritation reactions and not ACS. In order to verify this, two of the three subjects (and three previously unexposed control subjects) underwent diagnostic patch testTABLE 4 SUBJECTIRRITATION REACT~ONSTO 15% TRIPROLIDINE IN OLEIC ACID/PROPYLENE GLYCOL

INDIVIDUAL

Skin reaction grade” (hours post patch removal) Subject

2 hr

24 hr

48 hr

037 038 039 040 041 042

4.0 1.5 2.0 1.0 4.0 4.0

4.0 0.5 1.0 0.5 4.0 3.5

1.5 0.5 1.0 0.5 1.5 1.5

‘See Materials and Methods for grading scale.

TRIPROLIDINE

SKIN

IRRITATION

AND

109

SENSITIZATION

and Buehler, 1980). the drug/vehicle formulation as tested (12% TP) showed only questionable ACS potential under suggested interpretation guidelines (Robinson et al., 1990). The incidence of positive (grade > 1) skin reactions was 20% at challenge but declined to 10% at rechallenge. Under this exposure regimen, the vehicle (OA/PG) alone was not allergenic (Table 6, study No. 2). Using a more exaggerated nine induction patch exposure format (to more closely mimic clinical exposures). the drug/vehicle formulation as tested ( 12% TP) showed a much greater ACS response incidence (Table 6, Study No. 3). Here we observed a 50% incidence of positive responses at 24 or 48 hr post challenge patch removal, many of which were grade 2 severity (data not shown). Approximately half of the reactions observed at chal-

ing. This was conducted in two phases to protect the subjects (formula was tested in phase 2 only after initial testing of drug and vehicle components separately). Though some scattered l+ skin reactions were observed (Table 5) there was no indication from this testing that the subjects had become sensitized to the TP/OA/PG formula or any of the components. Their increased irritation reactions observed in the PK study were attributed to an enhancing effect of the higher drug concentration on the baseline OA/PG irritancy. Allergic contact sensitization. The potential for the TP/OA/PG formulation to induce and elicit ACS reactions was first evaluated using the Buehler guinea pig skin sensitization test (Ritz and Buehler, 1980; Robinson ef al., 1990). Using the standard three induction patch protocol (Table 6, Study No. 1) (Ritz TABLE

5

DIAGNOSTIC PATCH TEST RESULTS FOR SUBJECTS PRESENTING WITH STRONG IRRITATION REACTIONS TO 15% TRIPROLIDINE IN OLEIC ACID/PROPYLENE GLYCOL Subject 042h

041* Grading

Test Material

0.5

24

patch test results”

48

0.5

time point

24

OOlA’

OOZA’

(hours

post patch removal)

003A’

48

0.5

24

48

0.5

24

48

0.5

24

48

0 0 ? 0 0

? 0 0 0 0

0 0 ? 1 1+

0 0 0 0 ?

? 0 ? 0 0

0 0 ? ? ?

0 0 0 0 0

1+ 0 ? 0 0

? ?

? 0 7 0 1

? ?

0 0

? ?

? ?

0 0

0 ?

0 ?

l+ 1+

? ?

Phase I PG only 0.5%#OA in ETOH 0.5% OA in PG 0.075% SLS 0.15% SLS 5% TP in ETOH ETOH/water Saline

7 3 0 0 0 0 0 ? 1+ 0 ? 0 0 I+ 0 ? 0 0 000000000000?00 000

0 ? 0 0 0 ? 0 0 0 ? 000?00000000

A’ ?

000000000000

Phase 2 2.5% TPinOA/PG 5% TP in OA/PG PG only 0.5% OA in PG

? ? 000 ?

? ? 0

? ?

0 ? 0 ? 0?0000000?? 00?0000000???

’ See Materials and Methods for diagnostic ’ Previously exposed to 15% TP in OA/PG. ’ Naive control subjects.

patch test grading

scale.

? ? 0

110

ROBINSON

ET AL.

TABLE 6 GUINEA

PIG SKIN SENSITIZATION Number

Material Study No. 1 Triprolidine

Vehicle

Oleic acid

1% Oleic acid 99% propylene glYCO1 Ethanol

Triprolidine

Ethanol

Study No. 2 Oleic Acid Study No. 3 Triprolidine Oleic acid Triprolidine Triprolidine

TESTING

ACID/PROPYLENE

GLYCOL

of

induction patches 3

OF TRIPROLIDINE/~LEIC

[Induction]” 12%

[Challenge]”

Resultsh

12%

T: 4120 c: O/IO

[Recballenge]’

Resultsb

12%

T: 2120 c: O/6

0.5%

T: O/20 C: O/6 T: 2120 C: O/6

6%

Propylene glycol

3

1%

1%

T: O/20 c: O/IO

0.5%

T: O/20 C: O/6

1% Oleic acid 99% propylene glycol Propylene glycol Propylene glYCO1 Propylene glycol

9

12%

12%

T: 19140 c: o/20

12%

T: IO/40 C: O/6

0.5%

T: O/l9 C: O/6 T: 4120 c: O/6 T: O/l9 C: O/6

12% 9

30%

18%

T: Of20 c: O/IO

12%

a Concentration of test material under patch at induction, challenge, or rechallenge. b Results expressed as number of animals in test (T) or control (C) group with positive (grade > I) skin reactions over total number of animals tested.

lenge were confirmed by rechallenge under the identical test conditions, an observation that would be considered a positive indication of sensitization (Robinson et al., 1990). There were no skin reactions elicited in these same animals when rechallenged with the vehicle (OA/PG) alone. However, a small percentage of the test animals (20%) reacted at rechallenge to TP when delivered out of propylene glycol alone. The OA appeared to be a necessary component in order for the TP/OA/PG formulation to induce ACS in the guinea pig, since testing of TP (even at higher induction and challenge concentrations) in PG alone, at both induction and challenge, resulted in no positive skin reactions. Results of the three and nine induction patch Buehler testing suggested a minimal risk of inducing sensitization in human subjects from

single exposures necessary for PK evaluations. Consistent with this assessment, no ACS reactions were observed in PK study subjects exposed to various concentrations of TP ( 1- 15%) delivered out of a 0.5% OA/PG vehicle formula. The final cycle of the PK study required reexposure of subjects previously exposed to 5% TP in OA/PG. The exposures were separated by approximately 3 months. The skin reactions observed up to 48 hr post patch removal were typical of prior test cycles (skin reaction grades ranged from 0.5 to 2.0-data not shown). However, 4 days after patch removal one test subject (047) noted pruritic “welts” at the patch sites. These were examined 2 days later and characterized as “urticarial” and “erythematous.” The subject was given a topical corticosteroid and oral antihistamine and the lesions resolved over the next 4 days.

TRIPROLIDINE

SKIN

IRRITATION

Due to the delayed onset of this subject’s skin reaction, an allergic contact sensitization was suspected. Therefore, this subject and two previously unexposed control subjects underwent diagnostic patch testing. This testing (Table 7) included exposure to the drug formula and vehicle components, as well as the patch adhesive components (alone or in contact with drug formula), and control materials. Subject 047 presented with strong positive patch test reactions at all sites exposed to the drug formula, as well as weaker, but persistent, reactions to the OA/PG vehicle and to PG alone. The control subjects showed only expected transient irritation reactions to the formula and/or the OA/PG vehicle. Whether subject 047’s reactions to the OA/PG and PG alone represented true allergic reactivity to these vehicle components or simply enhanced irritation was not investigated by additional patch testing. Without such repeat testing, one also could not rule out “excited skin” reactivity (Bruynzeel and Maibach, 1986) as contributing to the reactions observed. Subject 047’s reactions to the TP/

PATCH REACTION

I

TEST RESULTS FOR SUBJECT WITH SUSPECTED SENSITIZATION TO TRIPROLIDINE/~LEIC ACID/PROPYLENE GLYCOL

Subject diagnostic

patch test results”

047b

004A ’

Grading

control

(hours

post patch removal)

24

48

96

0.5

24

72

+ saline + 5% TP in OA/PG

0 2+

0 3+

0 3+

0 2+

0 0

Saline

0

0

0

0

5% TP in OA/PG

2+ 2+ 0 0 2+ I+ 0

3+ 3+ 0 0 2+ 1+ 0

3+ 3+ 0 0 I?+ I+ 0

2+ 2+ 0 0 I+ 0 0

0 0 0 0 0 0 0 1+ ? 0.00

” See Materials and Methods for diagnostic patch test grading ” Previously exposed twice to 5% TP in OA/PG. ’ Naive

time point

005A’

0.5

Test material Transfer adhesive Transfer adhesive Foam adhesive + Foam adhesive + 5% TP in OA/PG 0.075% SLS 0.15% SLS Vehicle (OA/PG) PC only Saline

111

SENSITIZATION

OA/PG formula had increased with each subsequent exposure. This pattern of increased reactivity, his delayed response seen in the PK study, and the restriction of 3+ diagnostic patch test reactions to sites exposed to the TP/OA/ PG formula all suggested that subject 047 was sensitized. In view of the apparent sensitization of subject 047, a diagnostic patch test survey was conducted on 12 subjects previously exposed (once or twice) to the TP/OA/PG formula and 5 control subjects (Table 8). In this testing, 4 of 12 previously exposed subjects (017, 020, 023, and 024) showed evidence of sensitization to TP/OA/PG based on patch test reaction grades > I+ that persisted throughout 48 hr post patch removal or increased to I+ by the 48-hr grading time point. A second phase of patch testing (Table 9) in 3 of these 4 subjects (017, 020, and 024) showed confirmed or enhanced reactivity. In one case (subject 020) the reactions were atypical of allergic contact sensitization (more acneiform than papular or vesicular in appearance) and were equally severe

TABLE DIAGNOSTIC

AND

subjects.

scale.

0.5

24

72

0 0

0 0

0 0

0 0

0

0

?

0

0

0 ? 0 0 0 0 7

0 0 0 0 0 0

0 I+ 0 ? 2+ ?

0 0 0 0 ? 0 0

0 0 0 0 0 0 0

112

ROBINSON

ET AL.

TABLE DIAGNOSTIC

PATCH

TEST RESULTS

IN OLEIC

8

FOR SULUECTS

ACID/PROPYLENE

PREVIOUSLY

GLYCOL

Subject 020b

PG only 0.5% OA in ETOH/water 0.5% OA in PC 0.075% SLS 0.15% SLS 5% TP in OA/PG 5% TP in ETOH/water ETOH/water Saline

0.5

24

48

1+ 000 I+ 000 0 If 000 000 000

2+

1+

2+

I+

0 2+

0 1+

0.5

24

0 0 000000000 ? ? 0000?0000 0 0 ? 1+ 000000000 000000000 000000000

time point

023h (hours

24

48

0.5

24

48

0

?

?

0

0

0

0

0

?

?

?

0

?

?

0 1-t

0 I+

? 1+

? 1+

0 0

? I+

0 If

PG only 0.5% OA in ETOH/water 0.5% OA in PG 0.075% SLS 0.15% SLS 5% TP in OA/PG 5% TP in ETOH/water ETOH/water Saline

0.5

24

48

000 000 000 O?? 0?0???0??0?0??? 000 OO? 000 ? 0 0

0.5

24

48

48

? 000 ? 000 0 It? 000 ? 000

0

0

0

0

?

0 0

LI See Materials and Methods ’ Previously exposed twice to ’ Previously exposed once to d Previously exposed once to ’ Naive control subjects.

0

24

48

? ? 000000 ? ? ? ? 0 ? ? ? 0 0 0000?0 0 0

0

0

0

0

0 0 0 0 0

0 0 0 0 0

? ? ? ? 0

0 0 ? 0 0

0

0

0

0

016d (hours 48

026d

diagnostic

0.5

0.5

24

48

0.5

24

48

0 0 0 000000? O?? 0000??000 O?OO??O?? ?? ? 000000000 0000?00?0 000000000

(hours

010’

0 ?

post patch removal)

24

48

0.5

24

48

?

?

?

0

7 1+

?

I+?

? ? ?

?

I+?

?

I+?

for diagnostic patch test grading 5% TP in OA/PG. 15% TP in OA/PG. 5% TP in OA/PG.

0

013’

0.5

?

48

patch test results” 007’

time point 24

027d

post patch removal)

??? 0 0 000 ? ?

Grading 24

0.5

??O???O?? 000000000 000000000 ???000000

003’

0.5

0

24

48

?OO 0 0 ?OO ???

002’

PG only 0.5% OA in ETOH/water 0.5% OA in PG 0.075% SLS 0.15% SLS 5% TP in OA/PG 5% TP in ETOH/water ETOH/water Saline

0.5

24

??00?0000 0000?0000 ???O??O?O ??00?0000

Subject

Test material

time point

0.5

patch test results’

Olld

009d

039’

post patch removal)

0.5

Grading Test material

030h

48

Subject diagnostic 040’

TO TRIPROLIDINE

patch test resultsa

024h

Grading Test material

diagnostic

0176

EXPOSED

1 TESTING)

(PHASE

?

scale.

0.5 0 0 0 ??? O?? 0 0 0 ??O

24

48

0 0 0

0 0 0

? 0 0

? 0 0

0.5

24

48

? 0 1 0 0 7

? 0 ? ? ? 7

0 0 ? 0 0 7

0 0 0

0 0 ?

0 0 ?

TRIPROLIDINE

SKIN

IRRITATION

AND

TABLE

113

SENSITIZATION

9

DIAGNOSTIC PATCH TEST RESULTS FOR SUBJECTSPREVIOUSLYEXPOSED TO TRIPROLIDINE IN OLEIC ACID/PROPYLENE GLYCOL (PHASE 2 TESTING) Subject 020h

PG onl) 0.5% OA in ETOH/water 0.5% OA in PC 0.0750/ SLS 0.15% SLS 5% TP in OA/PG 5% TP in ETOH/water ETOH/water Saline

patch test results* 024*

017h Grading

Test material

diagnostic

time point

(hours

0.5

24

48

0.5

24

48

2+ 0 2+ 0

2+ 0 2f ?

2+ 0 2+ ?

? ? ? 0

? 0 0 0

0 0 0 0

9

9

?

?

2+ 0 0 0

2+ ? 0 0

2+ 0 0 0

1+ ? 0 0

1+ 0 0 0

020A ’

post patch removal) 0.5

24

48

0.5

24

48

1+ ? I+ 0

I+ 0 If 0

I+ 0 It 0

0 0 0 0

0 0 ? ?

0 0 0 0

0

?

?

?

0

?

?

I+d 0 0 0

3+ 2+ 0 0

3+ 2+ 0 0

2+ 1+ 0 0

? 0 0 0

? 0 0 0

? 0 0 0

’ See Materials and Methods for diagnostic patch test grading scale. ii Subjects with “positive” patch test results from phase 1 testing. ’ Naive control subject. ’ Reaction spreading from patch site

at patch sitesexposedto TP/OA/PG, OA/PG, and PG alone. In the other cases,the reactions either were restricted to the TP/OA/PG sites or were clearly more severe than reactions to the vehicle alone. One subject (024) showed strong cross-reactivity to TP alone (delivered out of ethanol) suggestingthat triprolidine itself had sufficient allergenicity to at least elicit an allergic reaction in certain subjects sensitized to the TP/OA/PG formula. As a result of the adverse skin reactions (irritant and allergic) observedin subjectsexposed to TP/OA/PG (aswell asto the OA/PG vehicle itself), this formula was rejected for further development. Parallel formulation development studies had demonstrated, however, that incorporation of as little as 1% TP into a pHcontrolled aqueous buffer (e.g., pH 7.0 phosphate buffer) would result in equal or better (and lessvariable) delivery of the drug (relative to 5%TP in OA/PG) in in vitro skin penetration studies(G. L. Manring, unpublished results;G. B. Kasting et ai., manuscript submitted for publication). On the basisof theseresults, clin-

ical irritation and sensitization studies were conducted on TP alone, delivered out of this simple vehicle. A seriesof three consecutive human irritation patch tests were conducted incorporating increasingduration of exposure to 1%TP. The seriesincluded a 24-hr occluded patch test, a 48-hr occluded patch test, and a three-patch test(eacha 24-hr occluded patch). The strongest skin irritation gradesobservedwere seenin the three-patch test and even here the highest average grade observed was only 0.2 on a O-4 scale(data not shown). Thus, the 1%TP/buffer formula was considered to be nonirritating. The next study conducted with this buffered TP formula was a 2 1-day cumulative irritation occluded patch test with a diagnostic patch test phasefor assessmentof possibleACS. In this study, patches were worn on the upper outer arm for approximately 22 hr, then removed just prior to visiting the test facility for skin grading and patch reapplication. Patcheswere to be worn over the weekend, and patch sites were to be moved in the event of any significant

114

ROBINSON

skin reactions (32 on the irritation grading scale). In general, three types of reaction patterns were observed as illustrated in Fig. 1. Subject 23 (Fig. 1A) showed a pattern of minimal irritation (range of grades = O-1.5) throughout the study. Of the 29 test subjects, 20 displayed this pattern of reactivity. Subject 5 (Fig. 1B) showed a unique pattern with peaks of persistent skin reactions (gradesashigh as2.5): however, the reactions rose and fell throughout the study indicative of cumulative irritation but not necessarilysensitization. In contrast, subject 22 (Fig. 1C) presented with strong reactions that developed only during the last week of testing and persisted long after the patches were removed, suggestiveof sensitization. Eight of the 29 test subjects presented with this pattern of skin reactions. Each of the test subjects underwent a diagnostic patch test 2 weeks after the final cumulative irritation patch test application. The reactionswere graded according to the standard HRIPT grading scale (Stotts, 1980; Robinson et al., 1989) in which persistent reactions receiving “E” gradesor greater (i.e., lE, 2E, 3E, 4, or 5) are considered indicative of allergic contact sensitization. The patcheswere applied to the backs of the subjects(well removed from the prior upper-arm patch sites) and only 1% TP/buffer and buffer alone were tested on opposite sidesof the back. This was done to minimize potential “excited skin” type reactions (Bruynzeel and Maibach, 1986). None of the 29 subjects tested showed any reaction to the buffer (data not shown). Nine of the 29 subjects presentedwith E grade skin reactions to the TP formula (Fig. 2). In one case(Subject 23) this wasa transient I E reaction unlikely to represent an allergic response.However, the other 8 subjects presented with persistent 1E to 3E reactions that persisted over the 72-hr post patch removal grading period. These latter reactions were highly indicative of an ACS to triprolidine. As a follow-up, seven of the cumulative irritation test subjects participated in an open application test to determine whether allergic skin reactions could be elicited under lessex-

ET AL.

4 [Al

SUBJECT

23

st--------------------------------i :: d c) 2---------------------------------. z :: ,--------------------------r

0

I”

’

-------

1-s

”

“’

IL.1

4 PI

SUBJECT

5

I [cl

SUBJECT

22

3-----

4

1111111

2345670 0

ORIGIN*L SITE

I

STUDY DAY MovESlTEIl

22 I 1 2 1zp MOVE SITE 12

FIG. I, Skin irritation grades assigned to 3 of 29 subjects exposed to 1% triprolidine in a pH 7.0 phosphate buffer in a 21-day cumulative irritation test. Skin grades were recorded after each 24-hr application period and just prior to patch reapplication. The patch sites were moved (laterally) any time a reaction grade of 2 or more was assigned. In such cases,the skin reactions at the new move site (as well as any residual reactions at the original site) were recorded.

treme exposure conditions. The subjects included five (Nos. 2, 7, 13, 22, and 25) with allergic-type reactions in the diagnostic patch

TRIPROLIDINE

SKIN

IRRITATION

AND

HOURS

5 i

: $ (3

POST PATCH I Lxxl KY

4

115

SENSITIZATION

REMOVAL

24 HOURS 48 HOURS 72 HOURS

3E 2E

Z

9 m

IE 2

0

2

7

13

14 SUBJECT

15

18

22

23

25

NUMBER

FIG. 2. Positive diagnostic patch test reactions to 1% triprolidine (in pH 7.0 phosphate buffer) among previous cumulative irritation patch test subjects. Skin reactions were graded using a standard HRIPT grading scale (Stotts, 1980: Robinson et al., 1989) (see Materials and Methods). Only subjects with at least one positive reaction (1 E or greater) are presented. All reactions to vehicle (buffer) alone were negative.

test, and two (Nos. 5 and 23) with negative diagnostic patch test results. As indicated in Table 10, all five of the diagnostic patch test positive subjects presented with allergic skin reactions in the open application test. In addition, the rapidity with which the reactions appeared (after commencing the application regimen) appeared to correlate with the severity of the prior diagnostic patch test reactions (compare Table 10 and Fig. 2). In contrast, the two patch test negative subjects showed no (Subject 23) or only minimal (Subject 5) evidence of elicited skin reactions in the open application test. The data from the diagnostic patch and open application tests confirmed the skin sensitization potential of transdermal TP when delivered out of a simple vehicle system. DISCUSSION A transdermal delivery system for the OTC antihistamine, triprolidine, might offer significant benefits to allergy sufferers in terms of both efficacy (more controlled delivery) and reduced sedation (avoiding peak plasma levels) (Simons et al., 1986; Peck et al., 1975; Carruthers et al., 1978). However, because of the

incidence of adverse skin reactions (irritation and allergic contact sensitization [ACS]) reported for transdermal drugs (Holdiness, 1989; Hogan and Maibach, 1990) and the concern around ACS reactions due to topical antihistamines (Fisher, 1986b), it was necessary to ascertain the potential of a transdermal TP formulation to cause toxic skin reactions that might preclude its widespread use. The data presented in this report document the ACS and irritation potentials of TP under occluded patch exposure conditions when delivered out of either a binary solvent transdermal vehicle (OA/PG) or a simple buffer. Preclinical skin irritation and sensitization testing provided only some indication of the ultimate clinical skin reactions observed. In the rabbit irritation test on the OA/PG vehicle system, there was an underestimation of the range of reactions later to be observed in clinical testing (compare Tables 1 and 2). This could reflect differences in species sensitivity (Campbell and Bruce, 198 1). It could also be a reflection of the number of animals tested (3 for each exposure duration) versus the number of clinical test subjects (16), since some of the clinical subjects did show weak irritation reactions even to the highest OA

116

ROBINSON TABLE 10

ET AL.

PK study, the plasma levels of TP observed were directly correlated with the degreeof skin irritation. This was especially noted for the three subjects (shown in Table 4) with grade 3.5-4.0 skin reactions after exposure to 15% Days from first TP in OA/PG (R. W. D’Souza, manuscript in Skin grade” application to Subject Days of observation of preparation). In general, it is unlikely that trinumber application Day 8 Day 15 skin reaction prolidine’s pharmacologic properties would greatly influence skin reactivity. If anything, 2 II I 2E.S’ 11 asan H- 1 antihistamine, TP might have weak 5 14 0 1EP’ IS anticholinergic effects that could result in a 7 4 3ESd 4 vasodilatory responsein the cutaneous micro13 4 2ESd 4 22 4 3ES 4 vasculature (Gilman et al., 1985). This could 14 0 N/A ’ 23 0 be particularly relevant at higher drug con25 12 I 2ESJ 12 centrations and might account for the increase in the erythema responsenoted at the 15%TP ’ See Materials and Methods for grading scale. b Skin reaction graded on Day 12-S” signifies dosein the pharmacokinetics study (Table 3). spreading papular/vesicular reaction. On the basisof the skin irritation observed, ’ “P” signifies papular reaction (confined to application technology development effort was directed site). towards reducing the skin irritation potential d Skin reaction graded on Day 4. of OA/PG (by incorporating other cosolvents, e Not applicable. ‘Skin reaction noted by subject on Day 12 but not emollients, and hydrating agents) without adgraded until Day IS. versely affecting OA/PG’s skin penetration enhancement properties (G. L. Manring, unpublished results). This effort, though producconcentration (3%) tested. The addition of 12 ing some limited success,was halted in the or 24% triprolidine to the OA/PG vehicle in- face of a more serious allergic contact sensicreased the irritation observed in the rabbit tization issue. irritation test especially in the 24-hr exposure Based upon objective criteria for interpretregimen (Table 1). Though the addition of 5% ing guinea pig skin sensitization test results TP to OA/PG had little effect on clinical ir- (Robinson et al., 1990) the results of the ritation scores(Table 3) the addition of 15% Buehler test on the TP/OA/PG formulation TP had a significant exacerbating effect (Tables were indicative of sensitization (Table 6). The 3 and 4) in concordance with the rabbit test magnitude of the responsewasalso dependent results. on the number of induction exposures, since In terms of clinical skin irritation potential, the standard Buehler test regimen (three inour operating assumption was that a mild de- duction patches) produced only a questionable gree of irritation (e.g., grade 3 1 on O-4 scale) indication of sensitization basedon suggested could be tolerated if;t represented only a tran- interpretation guidelines (Robinson et al.. sient erythema and produced no noticeable 1990). The incidence and severity of the symptoms (e.g., prutitus). Though many of the Buehler test results (particularly with the TP/ test subjects presented with only mild reac- OA/PG formulation) were, in general, an untions, the significant incidence of stronger derestimation of the magnitude of the sensi(agrade 2), persistent, and noticeably uncom- tization problem encountered in later clinical fortable reactions clearly indicated that the TP/ testing. In using the Buehler test procedure for OA/PG formula was unacceptable from a pri- risk assessmentpurposes for most consumer mary skin irritation standpoint. It was of in- products, there is generally a considerable exterest to note that, in many test subjects in the aggeration between the concentration of a OPEN APPLICATION TEST SKIN REACTIONS TO 1% TRIPROLIDINE IN SUBJECTS PREVIOUSLY SENSITIZED VIA REPEAT INSULT PATCH TESTING

TRIPROLIDINE

SKIN

IRRITATION

chemical as tested in animals and the concentration to which human subjects are exposed in subsequent human patch testing (Robinson et al., 1990; Robinson et al., 1989). There was little if any exaggeration possible in the testing of transdermal TP. Our findings on the disparity between the guinea pig test results and the clinical observations are important to consider in defining appropriate preclinical sensitization testing procedures for transderma1 drugs and formulations. The incidence and severity of clinical ACS reactions to TP/OA/PG was serious enough to discontinue this formulation development effort. Of six test subjects exposed twice to 5% TP in OA/PG (with exposures separated by approximately 3 months) in the PK study, five showed suggestive evidence of having become sensitized. In one case, this was manifested as a delayed pruritic, edematous skin reaction that appeared 4 days after patch removal in the PK study itself. Other cases only appeared upon standard diagnostic patch testing. Because of the number of patches applied in the diagnostic patch tests, one could interpret the resulting skin reactions to be possibly the result of an excited skin type of reactivity (Bruynzeel and Maibach, 1986). However, several of the clinical observations are directly supportive of a diagnosis of ACS. First, subject 047 presented with a classic delayed skin reaction that was further confirmed by diagnostic patch testing (Table 7). Second, all patch test positive subjects showed increased skin reactivity with each patch exposure. Third, there was a general lack of reactivity to SLS included as a standard irritant. Finally, each of the subjects showed selective or clearly preferential reactivity to patches containing the full TP/OA/ PC formulation (Tables 7-9). This suggested that the combination of drug (TP) plus vehicle (OA/PG) enhanced the allergenicity of the formulation relative to that of the individual components. On this basis, we interpreted these patch test results to be indicative of induced ACS to the TP/OA/PG formulation. As part of the overall technology development effort around a transdermal triprolidine

AND

SENSITIZATION

117

patch, skin penetration studies had shown that the drug could penetrate as well (and with less variability) out of a pH 7.0 buffer than out of the OA/PG vehicle (G. B. Kasting et al., manuscript submitted for publication). This provided a means to test the skin irritation and sensitization potential of the drug itself. When tested in this form, TP had virtually no primary irritation potential when tested under 24- or 48-hr, or three repeat 24-hr occluded patch test conditions (data not shown). The results of a 2 1-day cumulative irritation test demonstrated the allergenic potential of triprolidine, independent of the OA/PG vehicle system. Here, 8/29 (28%) subjects presented with delayed skin reactions indicative of ACS (Figs. 1 and 2) with many of the reactions confirmed by open application rechallenge (Table 10). The allergenic potential of TP appeared to be less when delivered out of a buffer than when delivered out of OA/PG (in which only two exposures likely sensitized 5 of 6 subjects). However, the risk of inducing ACS reactions at the incidence and severity observed was much greater than could be justified based on the benefit to be derived from a transdermal form of this drug. On this basis, all technology development effort was discontinued. Though there is not an abundance of experimental or case report data in the literature on antihistamine-induced ACS, there is still a prevailing view that these drugs have considerable contact allergenic potential (Fisher, 1986b). Our observations with TP, combined with recent findings that chlorpheniramine sensitized a significant number of subjects under HRIPT conditions (Amkraut and Shaw, 1988) lend support to this notion. A recent study reported on the pharmacokinetics of delivering triprolidine base from a proprietary transdermal device (Miles et al., 1990). They stated (no data presented) that mild to moderate pruritus was noted by certain subjects shortly after patch application or removal, a finding consistent with the irritation observed in our pharmacokinetics test subjects. This

118

ROBINSON

study did not include an evaluation of ACS potential. Our data clearly underscore the need to assess the skin toxicity of transdermal drug formulations early on in the development process. There is justified concern over the ability of preclinical sensitization test methods to exaggerate exposure sufficiently to be useful in risk assessment. Since most topical guinea pig methods rely on exaggeration in concentration (as well as occlusion in some cases), there is an obvious limitation in their utility for assessing the sensitization potential of relatively high concentrations of drugs designed for repeated occluded patch exposure. Though there have been some concerns over the use of adjuvant-based methods as being overly exaggerative of human exposure conditions for consumer products (Robinson et al., 1990; Robinson et al., 1989), these methods may provide a more suitable procedure for the evaluation of transdermal drugs. For clonidine, the use of the guinea pig maximization test (Magnusson and Kligman, 1969) was not predictive of this drug’s clinical sensitization potential (Goeptar et al., 1988). However, clonidine has additional anti-inflammatory and immunosuppressive effects (Goeptar et al., 1988; Robinson and Sozeri, 1990) that might have interfered with the ability to obtain accurate sensitization test data. It is clear that clinical test procedures, including extended duration predictive patch test methods (Maibath, 1985), will be of utmost importance in defining the sensitization risk of transdermal drugs. ACKNOWLEDGMENTS The authors are indebted to several individuals who contributed to the execution of these studies. We thank Dr. Barbara Fant of the New Drug Evaluation Unit (University of Cincinnati Medical Center), Dr. Richard W. D’Souza, and Dr. Robert K. Miday for their assistance in the planning and execution of several of the clinical evaluations. We also thank Dr. Miday, Ms. Jane Stotts, and Ms. Roberta Yerkes for their independent evaluations of many of the clinical skin reactions. We thank Dr. Eileen C. King for statistical analysis and support. We thank Ms.

ET AL. Cherie S. Maddin, Ms. Teresa J. Sozeri, and Mr. William J. Harvey for their involvement in clinical monitoring, assistance with data compilation, and technical assistance. Lastly, we thank Drs. Steven I. Katz and Howard I. Maibath for their helpful discussions during the course of these studies and for their critical review of the manuscript.

REFERENCES AMKRAUT, A., AND SHAW, J. E. (1988). Prevention 01 contact allergy by coadrninistration of a corticosteroid with a sensitizing drug. pp. l-13. European Patent Number 0282 156 A2. BALATO, N., CUSANO. F., LEMBO. G., AND AYALA. F. (1984). Ethylenediamine contact dermatitis. Contact Dermatitis II, 112-I 14. BRUYNZEEL, D. P., AND MAIBACH, H. I. ( 1986). Excited skin syndrome (angry back). Arch. Dermatol. 122,323328. CAMPBELL, R. L., AND BRUCE,R. D. (198 1). Comparative dermatotoxicology. 1. Direct comparison of rabbit and human skin irritation responses to isopropylmyristate. Toxicol. Appl. Pharmacol. 59, 555-563. CARRUTHERS, S. G., SHOEMAN, D. W., HIGNITE, C. E., AND AZARNOFF, D. L. (1978). Correlation between plasma diphenhydramine level and sedative and antihistamine effects.Clin. Pharmacol. Ther. 23, 375-380. CHIEN, Y. W., AND BANGA, A. K. (1989). Iontophoretic (transdermal) delivery of drugs: Overview of historical development. J. Pharm. Sci. 78, 353-354. FISHER,A. A. (1986a). The role of patch testing. In Contact Dermatitis (A. A. Fisher, Ed.), Vol. 3, pp. 9-29. Lea & Febiger, Philadelphia. FISHER,A. A. (1986b). Antihistamine dermatitis. In Contact Dermatitis (A. A. Fisher, Ed.), Vol. 3. pp. 2 1I-2 19. Lea & Febiger, Philadelphia. FREGERT, S. (I 98 1). Manual sf Contact Dermatitis. pp. 7 t-80. Year Book Med. Pub., Chicago. GILMAN, A. G.. GOODMAN, L. S.. RALL, R. W., AND MuRAD. F. (1985). The Pharmacological Basis of Therapeutics. pp. 135 and 620. Macmillan Co., New York. GOEPTAR. A. R.. DE GROOT, J.. LANG, M.. VAN TOL, R. G. L., AND SCHEPER,R. J. (1988). Suppressive effects of transdermal clonidine administration on contact hypersensitivity reactions in guinea pigs. Int. J. Immzfnopharmacol. IO, 277-282. GUY, R. H., HADGRAFT. J.. AND BUCKS, D. A. (1987). Transdermal drug delivery and cutaneous metabolism. Xenobiotica 17, 325-343. HOGAN,

D. J., AND

MAIBACH,

H. I. (1990).

Adverse

der-

matologic reactions to transdennal drug delivery systems. J. Am. Acad. Dermatol. 22, 81 l-814. HOLDINESS, M. R. ( 1989). A review of contact dermatitis associatedwith transdermal therapeutic systems.Contact Dermatitis 20, 3-9. MAGNUSSON, B.. AND KLIGMAN. A. M. (1969). The identification of contact allergens by animal assay. The

TRIPROLIDINE

SKIN

guinea pig maximization test. J. Invest. Dermatol.

IRRITATION 52,

268-276.

MAIBACH, H. I. (1985). Clonidine: irritant and allergic contact dermatitis assays.Contact Dermatitis 12, 192195. MAIBACH, H. I. (1986). Irritation, sensitization, photoirritation, and photosensitization assayswith a glyphosate herbicide. Contact Dermatitis 15, 152-l 56. MAIBACH, H. 1. (1987). Oral substitution in patients sensitized by transdermal clonidine treatment. Contacr Dermatitis

16, I-8.

MCCREESH, A. H., AND STEINBERG. M. (1987). Skin irritation testing in animals. In Dermatotoxicology (F. N. Marzulli and H. I. Maibach, Eds.). Vol. 3, pp. 153-172. Hemisphere. New York. MILES, M. V., BALASUBRAMANIAN, R., PITTMAN. A. W.. GROSSMAN. S. H.. PAPPA. K. A., SOUTH,M. F., WARGIN. W. A.. FINDLAY, J. W. A., POUST, R. I.. AND FROSOLONO, M. F. (1990). Pharmacokinetics of oral and transdermal triprolidine. J. Clin. Pharmacol. 30, 572575.

PECK, A. W.. FOWLE. A. S. E.. AND BYE, C. (1975). A comparison of triprolidine and clemistine on histamine antagonism and performance testsin man: Implications for the mechanism of drug-induced drowsiness. Eur. J. Clin. Phunnacol.

8. 455-463.

PHILLIPS, L.. STEINBERG, M., MAIBACH, H. I., AND AKERS, W. A. (1972). A comparison of rabbit and human skin response to certain irritants. To\-icol. .4ppl. Pharmacol.

21, 369-382.

RITZ. H. L., AND BUEHLER, E. V. (1980). Planning. conduct. and interpretation of guinea pig sensitization patch

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119

tests.In Current Cowepts in Cutaneous To,vicity (V. A. Drill and P. Lazar. Eds.), pp. 25-40. Academic Press, New York. ROBINSON,M. K., NUSAIR. T. L., FLETCHER,E. R., AND RITZ. H. L. (1990). A review of the Buehler guinea pig skin sensitization test and its use in a risk assessment process for human skin sensitization. Tosicology 61, 91-107. ROBINSON, M. K.. AND SOZERI. T. I. (1990). Immunosuppressive effectsof clonidine on the induction of contact sensitization in the Balb/c mouse. J. Invesr. Dcrmatol. 95, 587-59 1. ROBINSON.M. K., STOWS. J., DANNEMAN. P. J.. NUSAIR, T. L., AND BAY. P. H. S. (1989). A risk assessmentprocessfor allergic contact sensitization. Food Chem. Telicol. 27, 479-489.

SIDI, E., HINCKY. M., AND GERVAIS, A. (1955). Allergic sensitization and photosensitization to Phenergan cream. J. Invest. Dermatol. 24, 345-352. SIMONS,K. J.. SINGH. M.. GILLESPIE. C. A.. AND SIMONS, F. E. R. ( 1986). An investigation of the H 1-receptor antagonist triprolidine: Pharmacokinetics and antihistamine effects.J. Mer. Clin. Immunol. 27, 326-330. STOTTS, J. (1980). Planning, conduct, and interpretation human predictive sensitization patch tests. In Current Concepts in Culaneou.7 To,xicify (V. A. Drill and P. Lazar. Eds.). pp. 41-53. Academic Press, New York. TOSTI. A., BARDAZZI, F.. AND PIANCASTELLI, E. (1990). Contact dermatitis due to chlorpheniramine maleate in eyedrops. Contact Dermatitis 22, 55-55. VICKERS,C. F. H. (196 1). Dermatitis medicamentosa. Br. Med. J. 1, 1366-1367.