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Corneal Anesthetic Activity and Toxicity of Some Alkoxy Analogs of Thiocaine and Related Compounds*
Scientific Edition
JOURNAL OF THE AMERICAN PHARMACEUTICAL ASSOCIATION VOLUMEXLIV
JULY, I955
NUMBER 7 CONSECUTIVE No. 14
Corneal Anesthetic Activity and Toxicity of Some Alkoxy Analogs of Thiocaine and Related Compounds* By F. P. LUDUENA and JAMES 0. HOPPE Data are presented on the corneal anesthetic activity and systemic toaricity of 22 local anesthetics, including cocaine, tetracaine, dibucaine, procaine and Thiocainea and 2-alkoxy derivatives of the last two compounds. In the procaine as well as in the Thiocaineg series, 2-propoxy or higher alkoxy substitution greatly increased activity and toxicity with the increase in length of the alkoxy side chain. The thiolbenzoaces were considerably more active and toxic than the corresponding benzoates. WIN 4510, the 2-hexyloxy analog of Thiocainea, was found to be approximately 500 times as active as cocaine. The intravenous toxicity of this compound in mice was only 60 times greater than that of cocaine. HE INTRODUCTION of a propoxy or higher Talkoxy group in the 2-position of the procaine molecule results in a considerable increase in local anesthetic activity (14). The &ect of this substitution is greater on the corneal anesthetic activity than on the activity as determined by sciatic nerve block or the intracutaneous wheal methods in guinea pigs ( 2 4 ) . While procaine is less than one-tenth as active as cocaine when applied topically to the rabbit cornea, the 2-propoxy analog is equal to or slightly more active than cocaine. Activity can be increased still further by sulfur substitution of the non-carbonyl oxygen in the molecules of these 2-alkoxy procaine analogs (4, 5). In this paper the corneal anesthetic activity and the systemic toxicity of a group of diethylaminoethyl 4-amino-2-alkoxythiolbenzoatesand some related compounds is described. I n order
*
Received February 7 1955 from the Pharmacology Section, Sterling-Winthrop ’ Research Institute. Rensselaer,
N. Y.
The technical assistance of Mrs. N. Beglin, Miss P. Bourgault. Miss K. Kraft. and Mr. D. K. Seppelin is gratefully acknowledged.
to illustrate the effect of sulfur substitution, similar data (2) on the corresponding oxygen analogs have been included for comparative purposes. MATERIAL AND METHODS In Table I each compound is identified by its structural formula and name or WIN number. The WIN compounds, as well as Ravocainea and Sympocaine@,were synthesized by Clinton and his associates (6-8). Corneal Anesthesia.-The conjunctival sac of albino rabbits was filled with the solution (0.25-0.5 ml.). The lids were released after one minute and the excess solution was allowed to escape. There was no rinsing of the cornea. The wink reflex was provoked by application of the blunt point of a glass rod with a pressure sufficient to produce a slight depression of the cornea. Readings were taken at one and five minutes after instillation (two and six minutes, respectively, after the beginning of instillation) and every five minutes thereafter. A minimum of five animals was used for each concentration. A linear relationship between duration of anesthesia and the logarithm of the concentration was found, confirming Gerlough’s findings (9). The anesthetic concentration expected to produce anesthesia of five minutes’ duration (Threshold Anesthetic Concentrations or T A G ) was estimated
393
O( CH,)r-CH:,
WIN 4316 Tctracairieh Di bucaine Cocaine
n
....
....
....
\-/
dy/s)
I
CHI
Sps\ -/
I
HCI
HCI
HC1 HCI
2HC1
2HC1
6s) CH?
2HC1
HCI
HCI
23
2HC1
30 111 35 285
30
30 35
18
24
40 60
61 59 40 15 20 60 50 24
18 24
5 4 4
3
3
4
3
3
4
3
5 8 5 8 4 3 4 5 5 4
3
3
0.00035 0.01 0.0078 0 . 085c
0.00068
0.0016 0.029
0.0014
0.0012
0.26
0.21 1.2 0.0016 0.067 0.0008 0.027 0.032 0.00055 0.013 0.00017 0.0024 0.0034
210.0 8.5 11.0 1. o
125.0
53.0 2.9
60.0
70.0
0.3
0 4 0.07 53.0 1.3 110.0 3.2 2.7 150.0 6.5 500.0 36.0 25.0
---Corneal Anesthetic Activity (Rabbits)-No. ofTACE.,~ Cocaine 70 Ratioa Rabbits Doses
2HC1 HCI HzPOa HCI HCI HCI HCI HCI HCI HCI HCI H C1
Form Used
,?
Jy\
N S
\-
/ -
.“i
-
K(CzHa)z S(C2Hs)z R’(CzHsh N(C2Hs)z N(C?HL)P N(C&)z N(CzHs)z N(C2Hj)z N( C2H6)e S(C,Hs)? S(,-, CTHS)::
Ri
-
+
f 0.5 f 1.7 f 0.03 f 0.3 f 0.03 0.3 f 0.3 f 0.02 f 0.1 f 0.02 f 0.1 f 0.1
f 0.06
f 0.07
11 4 0 . 0 4
7.3 f 0.3 4 7 f 0.3 19.0 f 1 . 0
0.56 f 0.04
I)
1.0 f 0 . 0 7 3 . 0 f 0.3
0.7
0.7
16.0 f 1 . 2
7.70 52 0 0 53 6.0 0.53 3.6 5.1 0 45 2.5 0.32 1.8 1.1
1. o
4.0
2.6
34.0
43.0
19.0 6.3
27.0
27.0
1.2
2.5 0.36 36.0 2.9 36.0 5.3 3.7 42.0 7.6 60.0 10.0 17.0
,-Intravenous Toxicity (mice)Cocaine LDsa =ts.e. Ratioa mg./Kg.a
Values are given in term of the bases. b The TACs LDao values for these compounds have‘been published (2). They are included in this table for comparison with results obtained with the thiolbenzoate analogs. c This T A G value is somewhat lower than the one we published previously (2). I t was obtained after adding the results of a considerable number of tests.
2
O( CHI):-CHI
WIN 4336
S
O( CH?)>-CH?
WIN 3591b
2
3
S
O( CH?)---CHy
WIN 4338
S
2
S
O(CH>)J-CHB
WIN 4230
3
2
S
O(C H, )i-CHd
WIN 4205
0
3
0
0-CHI-CHj
~
WIN 369Sb
~~
0-CHP-CHI
2 2 2 2 2 2 2 2 2 2 2 3
S 0 S 0 S 0 0 S 0 S 0 S
x
-Structure----
Thiocaine Procaineb WIN 3766 Ravocaineb WIN 3800 Sympocaineb WIN 4071 ~. WIN 5334 W! N 5303 WIN 4510 WIN 4069b WIN 4229
Compound
I
NHz
TABLE I.-CORNEAL ANESTHETIC ACTIVITY A N D INTRAVENOUS TOXICITY
9 3
p
-1
2
;
2v
t
z a6
*
::
2
n
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$
2
r
4 0
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395
SCIENTIFIC EDITION
July, 1955
LL
0 c
Y
O.c)001
0.0I CONCENTRATION (Gm./100 ml.) Fig. 1.-Corneal anesthesia in rabbits.
0.001
by intra- or extrapolation from the regression lines. Cocaine ancsthetic ratios were obtained by dividing the TACs of cocaine by the T A G of the other compounds. The solutions were made by dissolving the compound in 0.9% saline solution, adjusting the PH to a value between 6.0 and 6.5 with 0.1 N NaOH and 0.1 N HCI. A further point needs t o be made in regard to the test used to determine topical anesthesia. As in all the experimental methods used so far, the effect of drugs tested is probably limited to the superficial layers of the cornea. More intense stimulation may damage the cornea, making accurate determinations more difficult. Toxicity.-Acute toxicity determinations were made by intravenous injections into male, Wehsterstrain, albino mice weighing 22 i 2 Gm. The compounds in aqueous solution were injected into groups of ten mice at each of three or more dose levels spaced at 0.1 logarithmic intervals. The rate of injection was maintained a t 1.0 ml. per minute and the volume injected restricted t o 0.35 4~0.15 ml. The LDso f its standard error was estimated by the method of Miller and Tainter (10).
RESULTS AND DISCUSSION The results are summarized in Table I. The doseresponse curves of some of the compounds are shown in Fig. 1. The effects of 2-alkoxy substitution in the molecular configuration of procaine and its thio-analog, ThiocaineB, in respect to corneal anesthetic activity and acute toxicity are summarized in the upper half of Table I. Replacement of the oxygen atom in the ester linkage of the procaine molecule by sulfur resulted in approximately a sixfold increase in both activity and toxicity. The addition of a 2-propoxy substituent resulted in an eighteen-fold increase in activity but only a sixfold increase in toxicity. The same group added t o Thiocaineq, however, resulted in a 130-fold increase in activity with only a thir-
0.I
I .O
teen-fold increase in toxicity. Although less dramatic, activity increased as the 2-alkoxy side chain in Thiocaines was lengthened with a n abrupt twofold increase in activity over its next lower homolog a t the 2-hexyloxg derivative (WIN 4510). Either no increase or, a t most, a 40% increase in acute toxicity was observed with each additional carbon throughout the lengthening of the 2-alkoxy side chain. A similar, and in each instance greater, increase in activity was observed in the corresponding oxygen (procaine) series with lengthening of the 2-alkoxy side chain. Acute toxicity increased but at a much slower rate than the increase in activity as the 2alkoxy side chain was extended in the procaine series. Lengthening of the 2-alkoxy side chain and substitution of the sulfur atom for oxygen atom in the ester linkage of procaine combined t o yield a compound with corneal anesthetic activity in the rabbit which was approximately 500 times as great as that of cocaine.' A moderate increase in activity was obtained by substitution of a methyl-piperidyl for the diethylamino group in the ThiocaineB series. A comparison of the activity and toxicity ratios (Table I ) shows that if the compounds are listed in order of increasing activity, with few exceptions a similar progressive increase in systemic toxicity is found. However, the activity/toxicity ratios (taking the cocaine activity/toxicity ratio as unity) varied from 0.16 for Thiocaines t o 8.3 for W I N 4510. In general, in the series of compounds studied, the greater the corneal anesthetic activity, the higher the activity/toxicity ratio. Thus, the most active eompounds were several times more active than toxic in relation to cocaine, whereas with the least active compounds tested, procaine and ThiocaineB, the intravenous toxicity greatly exceeded the topical anesthetic activity. ~. . - - .. 1 An erroneous value of 1,000 for the cocaine corneal anesthetic ratio of WIN 4.510 appeared in a publication from this laboratory (5). A correction was puhlished shortly thereafter IScience, 118,304(1953)1.
396
JOURNAL OF THE
AMERICANPHARMACEUTICAL ASSOCIATION
A much smaller range in the activity/toxicity ratios was found in a study of a large number of compounds (4) including those listed in Table I. in which the activity was determined by the intracutaneous wheal method of Biilbring and Wajda (11). In other words, there was in general a oloser relationship between the activity and toxicity procaine ratios. Undoubtedly, the weaker compounds in the present study were less able t o penetrate the cornea from the anesthetic solution during the time of exposure than the more active drugs, and therefore it may be assumed that in the case of the weakest compounds, the percentage absorbed by the corneal tissue was much lower than with the most active drugs. With the exception of procaine, ThiocaineB and WIN 3698, all the compounds were more active than cocaine. All the 2-alkoxythiolbenzoates were more active than dibucaine.
Vol. XLIV, No. 7
REFERENCES (1) Luduena, F. P., and Hoppe, J. O., Fed. Proc., 9. 297 (1950). (2) Luduena, F. P.,and Hoppe, J. O., J . Pharmacol. Erptl. Therap., 104, 40(1952). (3) Keil, W., Muschaweck, R., and Schmitz, H., Arsneirniftel-Forsch.,3, 6120953). (4) Luduena, F. P., and Hoppe, J. O., to be published. (5) Luduena, F. P., Clinton, R . O . , and Laskowski, S . C . , Science, 118, 138(1953). (ti) .Clinton, R. O . , Laskowski, S. C.. Salvador, U. J., and Wilson, M.. J . A m . Chem. Soc., 73, 3674(1951). (7) Clinton, R. O., Salvador, U. J., Laskowski, S . C., and Wilson, M., ibid.. 74, 592(1952). (8) Clinton, R. 0.. Salvador, U. J . , and Laskowski, S . C., ibid.. in press. (9) Gerlough, T. D., J . Pharmacol. Exptl. Therap., 41,307 11931). . . (10) Miller, L. C., and Tainter, M. L., Proc. Sac. Expfl. Biol. Med., 57, 261(1944). (11) Biilbring, E., and Wajda, I., J . Pharmacol. E x p f l . Therap.. 83, 78(1945).
Plasma Levels After the Oral Administration of Acetylsalicylic Acid and N-Acety1-p-Aminophenol in Different Forms to Human Subjects* By PIERRE EM. CARLO, NICHOLAS M. CAMBOSOS, GLORIA C. FEENEY, and PAUL K. SMITH When acetylsalicylic acid or N-acetyl-paminophenol was given t o human subjects the addition of an effervescent base resulted initially in higher plasma levels.
for some time (3, 4) that effervescent mixtures hasten the absorption of aspirin after oral administration. The present study was designed t o compare the plasma levels of salicylate from aspirin and of another analgesic drug, N-acetyl-p-aminophenol after their oral administration alone and with effervescent and alkaline adjuvants. T HAS BEEN KNOWN
I
EXPERIMENTAL In the aspirin experiments 12 normal subjects (one a woman) aged from twenty-one t o thirty-two years, and weighing from 123 t o 190 pounds, were employed. One blood sample was taken from each individual before drug administration to serve as a control. After fasting overnight the aspirin was administered orally in one single dose of 0.6 Gm. in one of the following forms: (a)as standard compressed tablets (Bayer) with 200 cc. of water, (b) in an effervescent base (Alka-Seltzer@)in 200 cc. of water, (c) as standard compressed tablets (Bayer) with 200 cc. of carbonated water (Canada Dry), and ( d ) as
standard compressed tablets (Bayer) plus 3.2 Gm. of sodium citrate with 200 cc. of water. In order to eliminate possible day-to-day variations in the absorption of the drug, an effort was made t o include all drug forms on each particular day of the experiment. Blood samples were taken by venipuncture a t twenty, forty-five, one hundred twenty, and three hundred minutes after drug administration. Blood was collected over oxalate t o prevent clotting and was centrifuged shortly afterward. In the N-acetyl-p-aminophenol experiments 12 normal male subjects, aged from twenty-one t o thirty-two years and weighing from 140 to 198 pounds, were employed. One blood sample was taken from each individual t o serve as a control. After fasting for at least six hours the drug was given orally with a glass of water. A dose of 0.3 Gm. of N-acetyl-p-aminophenol (Apamides, Ames) was administered and blood samples were withdrawn a t twenty, forty, sixty, and one hundred twenty minutes after ingestion of the drug. The experiment was performed once with ordinary Apamide and three days later with effervescent ApamideB. After the results observed in the first experiment it was decided t o use a dose of 0.6 Gm. and different time intervals. Blood samples were taken a t fifteen, thirty, ninety, and one hundred fifty minutes after ingestion of the drug. METHODS
* Received
December 29, 1954, from the Department of Pharmacology, The George Washington University School of Medicine Washington 5 D. C. Aided by grants from the'Miles Laboratories, Inc., and the Ames Company, Inc., Elkhart, Ind.
Salicylate levels were determined by a modification of the method described by Brodie, et aE. (2). The principal modification was the addition of a pH
JOURNAL OF THE AMERICAN PHARMACEUTICAL ASSOCIATION VOLUMEXLIV
JULY, I955
NUMBER 7 CONSECUTIVE No. 14
Corneal Anesthetic Activity and Toxicity of Some Alkoxy Analogs of Thiocaine and Related Compounds* By F. P. LUDUENA and JAMES 0. HOPPE Data are presented on the corneal anesthetic activity and systemic toaricity of 22 local anesthetics, including cocaine, tetracaine, dibucaine, procaine and Thiocainea and 2-alkoxy derivatives of the last two compounds. In the procaine as well as in the Thiocaineg series, 2-propoxy or higher alkoxy substitution greatly increased activity and toxicity with the increase in length of the alkoxy side chain. The thiolbenzoaces were considerably more active and toxic than the corresponding benzoates. WIN 4510, the 2-hexyloxy analog of Thiocainea, was found to be approximately 500 times as active as cocaine. The intravenous toxicity of this compound in mice was only 60 times greater than that of cocaine. HE INTRODUCTION of a propoxy or higher Talkoxy group in the 2-position of the procaine molecule results in a considerable increase in local anesthetic activity (14). The &ect of this substitution is greater on the corneal anesthetic activity than on the activity as determined by sciatic nerve block or the intracutaneous wheal methods in guinea pigs ( 2 4 ) . While procaine is less than one-tenth as active as cocaine when applied topically to the rabbit cornea, the 2-propoxy analog is equal to or slightly more active than cocaine. Activity can be increased still further by sulfur substitution of the non-carbonyl oxygen in the molecules of these 2-alkoxy procaine analogs (4, 5). In this paper the corneal anesthetic activity and the systemic toxicity of a group of diethylaminoethyl 4-amino-2-alkoxythiolbenzoatesand some related compounds is described. I n order
*
Received February 7 1955 from the Pharmacology Section, Sterling-Winthrop ’ Research Institute. Rensselaer,
N. Y.
The technical assistance of Mrs. N. Beglin, Miss P. Bourgault. Miss K. Kraft. and Mr. D. K. Seppelin is gratefully acknowledged.
to illustrate the effect of sulfur substitution, similar data (2) on the corresponding oxygen analogs have been included for comparative purposes. MATERIAL AND METHODS In Table I each compound is identified by its structural formula and name or WIN number. The WIN compounds, as well as Ravocainea and Sympocaine@,were synthesized by Clinton and his associates (6-8). Corneal Anesthesia.-The conjunctival sac of albino rabbits was filled with the solution (0.25-0.5 ml.). The lids were released after one minute and the excess solution was allowed to escape. There was no rinsing of the cornea. The wink reflex was provoked by application of the blunt point of a glass rod with a pressure sufficient to produce a slight depression of the cornea. Readings were taken at one and five minutes after instillation (two and six minutes, respectively, after the beginning of instillation) and every five minutes thereafter. A minimum of five animals was used for each concentration. A linear relationship between duration of anesthesia and the logarithm of the concentration was found, confirming Gerlough’s findings (9). The anesthetic concentration expected to produce anesthesia of five minutes’ duration (Threshold Anesthetic Concentrations or T A G ) was estimated
393
O( CH,)r-CH:,
WIN 4316 Tctracairieh Di bucaine Cocaine
n
....
....
....
\-/
dy/s)
I
CHI
Sps\ -/
I
HCI
HCI
HC1 HCI
2HC1
2HC1
6s) CH?
2HC1
HCI
HCI
23
2HC1
30 111 35 285
30
30 35
18
24
40 60
61 59 40 15 20 60 50 24
18 24
5 4 4
3
3
4
3
3
4
3
5 8 5 8 4 3 4 5 5 4
3
3
0.00035 0.01 0.0078 0 . 085c
0.00068
0.0016 0.029
0.0014
0.0012
0.26
0.21 1.2 0.0016 0.067 0.0008 0.027 0.032 0.00055 0.013 0.00017 0.0024 0.0034
210.0 8.5 11.0 1. o
125.0
53.0 2.9
60.0
70.0
0.3
0 4 0.07 53.0 1.3 110.0 3.2 2.7 150.0 6.5 500.0 36.0 25.0
---Corneal Anesthetic Activity (Rabbits)-No. ofTACE.,~ Cocaine 70 Ratioa Rabbits Doses
2HC1 HCI HzPOa HCI HCI HCI HCI HCI HCI HCI HCI H C1
Form Used
,?
Jy\
N S
\-
/ -
.“i
-
K(CzHa)z S(C2Hs)z R’(CzHsh N(C2Hs)z N(C?HL)P N(C&)z N(CzHs)z N(C2Hj)z N( C2H6)e S(C,Hs)? S(,-, CTHS)::
Ri
-
+
f 0.5 f 1.7 f 0.03 f 0.3 f 0.03 0.3 f 0.3 f 0.02 f 0.1 f 0.02 f 0.1 f 0.1
f 0.06
f 0.07
11 4 0 . 0 4
7.3 f 0.3 4 7 f 0.3 19.0 f 1 . 0
0.56 f 0.04
I)
1.0 f 0 . 0 7 3 . 0 f 0.3
0.7
0.7
16.0 f 1 . 2
7.70 52 0 0 53 6.0 0.53 3.6 5.1 0 45 2.5 0.32 1.8 1.1
1. o
4.0
2.6
34.0
43.0
19.0 6.3
27.0
27.0
1.2
2.5 0.36 36.0 2.9 36.0 5.3 3.7 42.0 7.6 60.0 10.0 17.0
,-Intravenous Toxicity (mice)Cocaine LDsa =ts.e. Ratioa mg./Kg.a
Values are given in term of the bases. b The TACs LDao values for these compounds have‘been published (2). They are included in this table for comparison with results obtained with the thiolbenzoate analogs. c This T A G value is somewhat lower than the one we published previously (2). I t was obtained after adding the results of a considerable number of tests.
2
O( CHI):-CHI
WIN 4336
S
O( CH?)>-CH?
WIN 3591b
2
3
S
O( CH?)---CHy
WIN 4338
S
2
S
O(CH>)J-CHB
WIN 4230
3
2
S
O(C H, )i-CHd
WIN 4205
0
3
0
0-CHI-CHj
~
WIN 369Sb
~~
0-CHP-CHI
2 2 2 2 2 2 2 2 2 2 2 3
S 0 S 0 S 0 0 S 0 S 0 S
x
-Structure----
Thiocaine Procaineb WIN 3766 Ravocaineb WIN 3800 Sympocaineb WIN 4071 ~. WIN 5334 W! N 5303 WIN 4510 WIN 4069b WIN 4229
Compound
I
NHz
TABLE I.-CORNEAL ANESTHETIC ACTIVITY A N D INTRAVENOUS TOXICITY
9 3
p
-1
2
;
2v
t
z a6
*
::
2
n
E$
$
2
r
4 0
w
w*
395
SCIENTIFIC EDITION
July, 1955
LL
0 c
Y
O.c)001
0.0I CONCENTRATION (Gm./100 ml.) Fig. 1.-Corneal anesthesia in rabbits.
0.001
by intra- or extrapolation from the regression lines. Cocaine ancsthetic ratios were obtained by dividing the TACs of cocaine by the T A G of the other compounds. The solutions were made by dissolving the compound in 0.9% saline solution, adjusting the PH to a value between 6.0 and 6.5 with 0.1 N NaOH and 0.1 N HCI. A further point needs t o be made in regard to the test used to determine topical anesthesia. As in all the experimental methods used so far, the effect of drugs tested is probably limited to the superficial layers of the cornea. More intense stimulation may damage the cornea, making accurate determinations more difficult. Toxicity.-Acute toxicity determinations were made by intravenous injections into male, Wehsterstrain, albino mice weighing 22 i 2 Gm. The compounds in aqueous solution were injected into groups of ten mice at each of three or more dose levels spaced at 0.1 logarithmic intervals. The rate of injection was maintained a t 1.0 ml. per minute and the volume injected restricted t o 0.35 4~0.15 ml. The LDso f its standard error was estimated by the method of Miller and Tainter (10).
RESULTS AND DISCUSSION The results are summarized in Table I. The doseresponse curves of some of the compounds are shown in Fig. 1. The effects of 2-alkoxy substitution in the molecular configuration of procaine and its thio-analog, ThiocaineB, in respect to corneal anesthetic activity and acute toxicity are summarized in the upper half of Table I. Replacement of the oxygen atom in the ester linkage of the procaine molecule by sulfur resulted in approximately a sixfold increase in both activity and toxicity. The addition of a 2-propoxy substituent resulted in an eighteen-fold increase in activity but only a sixfold increase in toxicity. The same group added t o Thiocaineq, however, resulted in a 130-fold increase in activity with only a thir-
0.I
I .O
teen-fold increase in toxicity. Although less dramatic, activity increased as the 2-alkoxy side chain in Thiocaines was lengthened with a n abrupt twofold increase in activity over its next lower homolog a t the 2-hexyloxg derivative (WIN 4510). Either no increase or, a t most, a 40% increase in acute toxicity was observed with each additional carbon throughout the lengthening of the 2-alkoxy side chain. A similar, and in each instance greater, increase in activity was observed in the corresponding oxygen (procaine) series with lengthening of the 2-alkoxy side chain. Acute toxicity increased but at a much slower rate than the increase in activity as the 2alkoxy side chain was extended in the procaine series. Lengthening of the 2-alkoxy side chain and substitution of the sulfur atom for oxygen atom in the ester linkage of procaine combined t o yield a compound with corneal anesthetic activity in the rabbit which was approximately 500 times as great as that of cocaine.' A moderate increase in activity was obtained by substitution of a methyl-piperidyl for the diethylamino group in the ThiocaineB series. A comparison of the activity and toxicity ratios (Table I ) shows that if the compounds are listed in order of increasing activity, with few exceptions a similar progressive increase in systemic toxicity is found. However, the activity/toxicity ratios (taking the cocaine activity/toxicity ratio as unity) varied from 0.16 for Thiocaines t o 8.3 for W I N 4510. In general, in the series of compounds studied, the greater the corneal anesthetic activity, the higher the activity/toxicity ratio. Thus, the most active eompounds were several times more active than toxic in relation to cocaine, whereas with the least active compounds tested, procaine and ThiocaineB, the intravenous toxicity greatly exceeded the topical anesthetic activity. ~. . - - .. 1 An erroneous value of 1,000 for the cocaine corneal anesthetic ratio of WIN 4.510 appeared in a publication from this laboratory (5). A correction was puhlished shortly thereafter IScience, 118,304(1953)1.
396
JOURNAL OF THE
AMERICANPHARMACEUTICAL ASSOCIATION
A much smaller range in the activity/toxicity ratios was found in a study of a large number of compounds (4) including those listed in Table I. in which the activity was determined by the intracutaneous wheal method of Biilbring and Wajda (11). In other words, there was in general a oloser relationship between the activity and toxicity procaine ratios. Undoubtedly, the weaker compounds in the present study were less able t o penetrate the cornea from the anesthetic solution during the time of exposure than the more active drugs, and therefore it may be assumed that in the case of the weakest compounds, the percentage absorbed by the corneal tissue was much lower than with the most active drugs. With the exception of procaine, ThiocaineB and WIN 3698, all the compounds were more active than cocaine. All the 2-alkoxythiolbenzoates were more active than dibucaine.
Vol. XLIV, No. 7
REFERENCES (1) Luduena, F. P., and Hoppe, J. O., Fed. Proc., 9. 297 (1950). (2) Luduena, F. P.,and Hoppe, J. O., J . Pharmacol. Erptl. Therap., 104, 40(1952). (3) Keil, W., Muschaweck, R., and Schmitz, H., Arsneirniftel-Forsch.,3, 6120953). (4) Luduena, F. P., and Hoppe, J. O., to be published. (5) Luduena, F. P., Clinton, R . O . , and Laskowski, S . C . , Science, 118, 138(1953). (ti) .Clinton, R. O . , Laskowski, S. C.. Salvador, U. J., and Wilson, M.. J . A m . Chem. Soc., 73, 3674(1951). (7) Clinton, R. O., Salvador, U. J., Laskowski, S . C., and Wilson, M., ibid.. 74, 592(1952). (8) Clinton, R. 0.. Salvador, U. J . , and Laskowski, S . C., ibid.. in press. (9) Gerlough, T. D., J . Pharmacol. Exptl. Therap., 41,307 11931). . . (10) Miller, L. C., and Tainter, M. L., Proc. Sac. Expfl. Biol. Med., 57, 261(1944). (11) Biilbring, E., and Wajda, I., J . Pharmacol. E x p f l . Therap.. 83, 78(1945).
Plasma Levels After the Oral Administration of Acetylsalicylic Acid and N-Acety1-p-Aminophenol in Different Forms to Human Subjects* By PIERRE EM. CARLO, NICHOLAS M. CAMBOSOS, GLORIA C. FEENEY, and PAUL K. SMITH When acetylsalicylic acid or N-acetyl-paminophenol was given t o human subjects the addition of an effervescent base resulted initially in higher plasma levels.
for some time (3, 4) that effervescent mixtures hasten the absorption of aspirin after oral administration. The present study was designed t o compare the plasma levels of salicylate from aspirin and of another analgesic drug, N-acetyl-p-aminophenol after their oral administration alone and with effervescent and alkaline adjuvants. T HAS BEEN KNOWN
I
EXPERIMENTAL In the aspirin experiments 12 normal subjects (one a woman) aged from twenty-one t o thirty-two years, and weighing from 123 t o 190 pounds, were employed. One blood sample was taken from each individual before drug administration to serve as a control. After fasting overnight the aspirin was administered orally in one single dose of 0.6 Gm. in one of the following forms: (a)as standard compressed tablets (Bayer) with 200 cc. of water, (b) in an effervescent base (Alka-Seltzer@)in 200 cc. of water, (c) as standard compressed tablets (Bayer) with 200 cc. of carbonated water (Canada Dry), and ( d ) as
standard compressed tablets (Bayer) plus 3.2 Gm. of sodium citrate with 200 cc. of water. In order to eliminate possible day-to-day variations in the absorption of the drug, an effort was made t o include all drug forms on each particular day of the experiment. Blood samples were taken by venipuncture a t twenty, forty-five, one hundred twenty, and three hundred minutes after drug administration. Blood was collected over oxalate t o prevent clotting and was centrifuged shortly afterward. In the N-acetyl-p-aminophenol experiments 12 normal male subjects, aged from twenty-one t o thirty-two years and weighing from 140 to 198 pounds, were employed. One blood sample was taken from each individual t o serve as a control. After fasting for at least six hours the drug was given orally with a glass of water. A dose of 0.3 Gm. of N-acetyl-p-aminophenol (Apamides, Ames) was administered and blood samples were withdrawn a t twenty, forty, sixty, and one hundred twenty minutes after ingestion of the drug. The experiment was performed once with ordinary Apamide and three days later with effervescent ApamideB. After the results observed in the first experiment it was decided t o use a dose of 0.6 Gm. and different time intervals. Blood samples were taken a t fifteen, thirty, ninety, and one hundred fifty minutes after ingestion of the drug. METHODS
* Received
December 29, 1954, from the Department of Pharmacology, The George Washington University School of Medicine Washington 5 D. C. Aided by grants from the'Miles Laboratories, Inc., and the Ames Company, Inc., Elkhart, Ind.
Salicylate levels were determined by a modification of the method described by Brodie, et aE. (2). The principal modification was the addition of a pH