- Email: [email protected]
Effect of various conditions on the sublingual absorption of para-aminosalicylic acid
Effect of various conditions on the sublingual absorption of para-aminosalicylicacid Thomas J. De Marco, B.S., D.M.D., Ph.D.,* and Inger Blomsnes, Clevelund, Ohti CASE WESTERN RESERVE UNIVERSITY
SCHOOL OF DENTISTRY
This study was undertaken to determine the effect of different solvent bases and conditions on the sublingual absorption of para-aminosalicylic acid. A standard sublingual dose of 500 mg. in 1.0 C.C. of vehicle was administered to white adult male rabbits. Measurable concentrations of PAS were present in the blood as early as 10 minutes after administration, and peak concentrations occurred in 80 minutes. The total absorption of PAS was 34.8 per cent in a period of 160 minutes. The amount and degree of drug absorbed were decreased slightly by the use of sucrose, ethyl alcohol, or vegetable oil as a vehicle. Both alcohol and vegetable oil increased the rate of absorption, as was evidenced by an earlier peak of absorption. Experiments in which the jugular vein was ligated bilaterally still showed that 21 per cent of the administered dose was absorbed in the experimental period. Such absorption was presumed to be through the lymphatic system. The sublingual route would not appear to be an effective way of administering PAS clinically, since it is absorbed more completely orally.
T
his study was undertaken to determine the effect of different solvent bases upon the sublingual absorption of para-aminosalicylic acid (PAS). Originally, the research project was to determine the degree of lymphatic participation in the sublingual absorption of drugs. It was technically impossible to cannulate the cervical lymphatic duct; therefore, the research protocol had to be modified. The mucous membrane of the oral cavity has a rich supply of blood and lymphatic vessels. Accordingly, this mucosa, especially in the sublingual area, This study was supported Office of Seientiflc Research. *Professor of Pharmacology
320
by Grant
AFOSR-70-1841
and Periodontics
from
and Associate
the United Dean.
States
Air
Force
Volume Number
37 2
Sublingual
absorption
of PAS
321
has been used as a site for the local application of drugs to gain access to the systemic circulation. The sublingual area offers a clinically efficacious and easily accessible route for administering drugs and has been utilized for hundreds of years. One of the early publications on this route of administration was by Karmel,* in which he reported the rapid absorption of nicotine from the sublingual area. Numerous investigators studied the sublingual administration of drugs, and an excellent tabulation of these works is presented in a paper by Katz and Barr.3 The majority of these works employed bioassay methods (usually a clinically observable effect) as criteria for the absorption of the drug, as opposed to chemical assays. Many of the results were also complicated by failure to control aspiration and/or swallowing of the drug(s). In the present study, chemical assay methods were used to determine the time course of absorption and the total amount of drug absorbed. The most recent, thorough studies in this field were those carried out by Katz and Barr3-5 in 1955. They controlled any additional absorptive processes by ligating the esophagus and cannulating the trachea in the cervical region. The drugs were administered in solution and in solid form in both rats and mice. They found that the vehicle and the form of an alkaloid (for example, strychnine) play a more important role in sublingual absorption than in oral absorption. This finding was in direct contrast to that of Waltoqs who claimed that there was no difference in the absorption of an alkaloid or its salts and that one type of solvent was no different from any other. Katz and Barr also found that these characteristics (vehicle and form) must be varied for each drug in order to provide maximum absorption. Similar results were obtained with regard to the use of tablet bases, in that independent analysis must be conducted for each agent. A thorough study using a highly water-soluble, rapidly absorbed compound (para-aminosalicylic acid) was undertaken to determine the extent of its sublingual absorption and the effect of various changes on the degree of this absorption. MATERIALS AND METHODS White adult male rabbits of the New Zealand strain were anesthetized with pentobarbital sodium by intraperitoneal injection (40 mg. per kilogram). The weight of the animals varied from 2.0 to 3.0 kilograms. A tracheotomy and an esophageal cannulation were performed to ensure that no drug could be aspirated or swallowed. Following this procedure, the animal was placed in a special restraining cage. The standard sublingual dose of sodium-para-aminosalicylic acid (Pamisyl, Parke Davis & Company, Detroit, Michigan) was 500 mg. in 1 cc. of distilled water or other vehicle. Blood samples were taken at the end of timed intervals from either the ear vein or the sciatic vein in the left leg. The concentration of drug in whole blood was determined at the end of each timed interval. When the concentration of drug in plasma was determined
322
De Marco and Bkm..s~~es
Oral Surg. F’ehruary, 1974
FQ. 1. Distribution of PAS in blood at various times after the sublingual administration of 500 mg. in 1 C.C. distilled water. The points at each time interval represent the mean values of six experiments, with the vertical bars representing the associated standard deviation.
for the final sample, the percentage of drug in the plasma was calculated for that animal as follows : Plasma concentration x ( 1.0 hematocrit) x 100) /blood concentration = % in plasma The concentration of drug in plasma at intermediate time periods was then calculated from the data obtained for the final sample. The remaining drug solution in the mouth was aspirated and analyzed. The content of para-aminosalicyclic acid in blood and plasma was determined acid. by the method of Way and associate@ for “free” para-amino-salicylie Samples were read in a Bausch and Lomb calorimeter at a wavelength of 540 mp. RESULTS Distilled water
Five hundred milligrams of para-aminosalicyclic acid (PAS) in 1 cc. of distilled water was placed in the floor of the mouth. The distribution of the para-aminosalicylic acid in the blood is illustrated in Fig. 1. Peak absorption was evident 80 minutes after administration, Upon aspiration of the drug remaining in the floor of the mouth, the total amount of drug absorbed was 174 + 12.3 mg. (34.8 per cent). The absorption from the sublingual area was rapid, with
Volume 37 Number 2
Sublingual
I IO TIME
I 20
I 30
I 40
I 50
1 60
1 jr0
I 80
1 90
1 100
of PAS
absorption
1 110
1
1
1
,
120
130
I40
150
323
1 160
Winurss)
Fig. 8. Distribution of PAS in blood at various times after the sublingual administration of 500 mg. in 96 per cent ethyl alcohol. The points at each time interval represent the mean values of six experiments, with the vertical bars representing the associated standard deviation.
measurable blood concentration administration. Ethyl
being achieved as early as 10 minutes
after
alcohol
With the distilled water experiments serving as a base line, various other solutes were tested to determine if this absorption could be altered. In one group of experiments, the para-aminosalicyclic acid was dissolved in 96 per cent alcohol. Again, 1 C.C. of the alcohol solution (500 mg.) was placed sublingually following the cannulation procedures. The distribution of PAS in the blood under this condition is illustrated in Fig. 2. It is apparent that the ethyl alcohol did not significantly alter the absorption or distribution of the PAS. The total amount of drug absorbed was decreased to 26 per cent (131 mg.). The rate of absorption did appear to be affected, with the peak absorption occurring at 40 minutes instead of 80 minutes. Sucrose
In this group of experiments, the PAS was dissolved in a saturated solution of sucrose and administered in a 1 C.C. dose sublingually (500 mg.). The distribution curve is shown in Fig. 3. Again, there was no significant effect upon the distribution or absorption of the PAS (28 per cent absorbed).
324
Oral February,
De Marco and Blonunes
surg. 1974
BLOOD PAS GQ,CC 60
c 5
III1 10
I 20
30
40
SO
I1 60
1 70
80
II 90
11 100
110
120
I
I
!
130
140
150
1 160
T1.W. (54inut.s)
S. Distribution of PAB in blood at various times after the sublingual administration of 500 mg. in saturated sucrosesolution. The points at each time interval represent the mean values of six experiments,with the vertical bars representing the associated standard deviation. Fig.
Vegetable
oil
The experiments were repeated, using vegetable oil as a base. The amount absorbed was decreased to 23.2 per cent, and the peak absorption time occurred in 40 minutes instead of 80 minutes. Venous
occlusion
The jugular veins were tied off bilaterally in order to determine, by indirect means, whether the lymphatic system played any role in the absorption of PAS sublingually. In this manner, any drug that was absorbed would have to have passed through the lymphatic system. The resultant distribution curve is shown in Fig. 4. The total amount of drug absorbed was decreased to 21 per cent (108 mg.). It is assumed that any drug absorbed had to pass through the lymphatic system in order to gain access to the systemic circulation. The results of these five series of experiments are summarized in Table I. The percentage of drug in the plasma was 61.2 per cent + 6.9 per cent for all the experiments. This is in accord with our previous experiments.l DISCUSSION
It has been shown that PAS can be readily absorbed from the sublingual area. Changes in the different solvent bases appear to decrease the absorption slightly.
Volume 37 Number 2
Sublingual
absorption
of PAS
325
BLOOD PASS/H*0 mcgfcc
10
,?D
M
40
50
60
70
80
90
100
110
120
130
140
150
160
TIME (Minutes)
Fig. 4. Distribution of PAS in blood at various times after the sublingual administration of 500 mg. in 1 C.C. distilled water with the jugular veins tied off bilaterally. The points at each time interval represent the mean values of six experiments, with the vertical bars representing the associated standard deviation.
Table I. Effect of various conditions on the sublingual Peak concentrationt Peak time Condition* (?nog./c.c.) (minutes) 80 Water 45.5 + 10.0 40 Vegetable oil 39.0 ? 11.0 40 Ethyl alcohol 40.1 2 7.1 80 Sucrose 42.5 2 9.4 80 Venous occlusion 10.6 + 4.8 "500 mg. in 1.0 C.C.of vehicle. tIn blood. tsignificantly different from water, p < 0.05.
absorption of PAS
Amount remaining in mouth 326.5 k 22.9 384.3 2 35.4 369. 2 29.9 359. 2 22.9 391. ? 13t
Per cent absorbed 34.8 23.2 26.2 28.2 21.8
Both vegetable oil and alcohol changed the peak absorption time from 40 to 80 minutes. Ligation of the jugular veins bilaterally inhibited this absorption, but a significant amount of the drug was still absorbed. It is assumed that the drug had to be absorbed through the lymphatic system. In our earlier studies,’ we had found that ligation of the superior mesenteric vein did not completely inhibit the intestinal absorption of PAS. Under these conditions, 22.7 per cent of the administered dose was still absorbed. It was assumed in that case and in the present study that the material can gain access to the systemic circulation either through the lymphatic system directly or through lymphaticovenous communications made patent by the blood vessel
326
De Marco an.d Blomsnes
Oral February,
Slug. 1974
constriction. Such lymphaticovenous communications have been previously documented by several investigationsG, i Other experiments are obviously indicated in which the lymphatic vessels are cannulated so that the amount of participation of the lymphatic system in this absorption can be accurately assessed. The sublingual absorption of PAS would not appear to be a practical means of administering the drug clinically, since the compound is absorbed well orally (80 per cent orally versus 30 per cent sublingually). However, the foregoing experiment will serve as a model or base line from which to compare the sublingual absorption of other compounds. In such a survey, it would be hoped that sublingual administration would be found to be an effective route for administering some drugs. REFERENCES 1. De Marco,
Thomas J., and Levine, Ruth R.: J. Pharmacol. Exp. Ther. 169: 142-151, 1969. 2. Karmel, J.: Dtsch. Arch. Klin. Med. 12: 466-488, 1873. 3. Katz, M., and Barr, M.: J. Am. Pharm. Assoc. 44: 419-423, 1955. 4. Katz, M., and Barr, M.: J. Am. Pharm. Assoc. 44: 472-476, 1955. Katz, M., and Barr, M.: J. Am. Pharm. Assoc. 44: 476-480, 1955. ii: Roddenberry, H., and Allen, L.: Anat. Rec. 159: 147-158, 1967. Threefoot, 8. A., Kent, W. T., and Hatchett, B. F.: J. Lab. Cl&. Med. 61: 9-22, 1963. L: Walton, R. P.: J. A. M. A. 124: 138, 1944. 9. Way, E. L., Smith, P. K., Howie, D. L., Weiss, R., and Swanson, R.: J. Pharmacol. Exp. Ther. 93: 368-382, 1948. Reprint
requests
to :
Dr. Thomas J. De Marco Case Western Reserve University School of Dentistry 2123 Abington Road Cleveland, Ohio 44106
SCHOOL OF DENTISTRY
This study was undertaken to determine the effect of different solvent bases and conditions on the sublingual absorption of para-aminosalicylic acid. A standard sublingual dose of 500 mg. in 1.0 C.C. of vehicle was administered to white adult male rabbits. Measurable concentrations of PAS were present in the blood as early as 10 minutes after administration, and peak concentrations occurred in 80 minutes. The total absorption of PAS was 34.8 per cent in a period of 160 minutes. The amount and degree of drug absorbed were decreased slightly by the use of sucrose, ethyl alcohol, or vegetable oil as a vehicle. Both alcohol and vegetable oil increased the rate of absorption, as was evidenced by an earlier peak of absorption. Experiments in which the jugular vein was ligated bilaterally still showed that 21 per cent of the administered dose was absorbed in the experimental period. Such absorption was presumed to be through the lymphatic system. The sublingual route would not appear to be an effective way of administering PAS clinically, since it is absorbed more completely orally.
T
his study was undertaken to determine the effect of different solvent bases upon the sublingual absorption of para-aminosalicylic acid (PAS). Originally, the research project was to determine the degree of lymphatic participation in the sublingual absorption of drugs. It was technically impossible to cannulate the cervical lymphatic duct; therefore, the research protocol had to be modified. The mucous membrane of the oral cavity has a rich supply of blood and lymphatic vessels. Accordingly, this mucosa, especially in the sublingual area, This study was supported Office of Seientiflc Research. *Professor of Pharmacology
320
by Grant
AFOSR-70-1841
and Periodontics
from
and Associate
the United Dean.
States
Air
Force
Volume Number
37 2
Sublingual
absorption
of PAS
321
has been used as a site for the local application of drugs to gain access to the systemic circulation. The sublingual area offers a clinically efficacious and easily accessible route for administering drugs and has been utilized for hundreds of years. One of the early publications on this route of administration was by Karmel,* in which he reported the rapid absorption of nicotine from the sublingual area. Numerous investigators studied the sublingual administration of drugs, and an excellent tabulation of these works is presented in a paper by Katz and Barr.3 The majority of these works employed bioassay methods (usually a clinically observable effect) as criteria for the absorption of the drug, as opposed to chemical assays. Many of the results were also complicated by failure to control aspiration and/or swallowing of the drug(s). In the present study, chemical assay methods were used to determine the time course of absorption and the total amount of drug absorbed. The most recent, thorough studies in this field were those carried out by Katz and Barr3-5 in 1955. They controlled any additional absorptive processes by ligating the esophagus and cannulating the trachea in the cervical region. The drugs were administered in solution and in solid form in both rats and mice. They found that the vehicle and the form of an alkaloid (for example, strychnine) play a more important role in sublingual absorption than in oral absorption. This finding was in direct contrast to that of Waltoqs who claimed that there was no difference in the absorption of an alkaloid or its salts and that one type of solvent was no different from any other. Katz and Barr also found that these characteristics (vehicle and form) must be varied for each drug in order to provide maximum absorption. Similar results were obtained with regard to the use of tablet bases, in that independent analysis must be conducted for each agent. A thorough study using a highly water-soluble, rapidly absorbed compound (para-aminosalicylic acid) was undertaken to determine the extent of its sublingual absorption and the effect of various changes on the degree of this absorption. MATERIALS AND METHODS White adult male rabbits of the New Zealand strain were anesthetized with pentobarbital sodium by intraperitoneal injection (40 mg. per kilogram). The weight of the animals varied from 2.0 to 3.0 kilograms. A tracheotomy and an esophageal cannulation were performed to ensure that no drug could be aspirated or swallowed. Following this procedure, the animal was placed in a special restraining cage. The standard sublingual dose of sodium-para-aminosalicylic acid (Pamisyl, Parke Davis & Company, Detroit, Michigan) was 500 mg. in 1 cc. of distilled water or other vehicle. Blood samples were taken at the end of timed intervals from either the ear vein or the sciatic vein in the left leg. The concentration of drug in whole blood was determined at the end of each timed interval. When the concentration of drug in plasma was determined
322
De Marco and Bkm..s~~es
Oral Surg. F’ehruary, 1974
FQ. 1. Distribution of PAS in blood at various times after the sublingual administration of 500 mg. in 1 C.C. distilled water. The points at each time interval represent the mean values of six experiments, with the vertical bars representing the associated standard deviation.
for the final sample, the percentage of drug in the plasma was calculated for that animal as follows : Plasma concentration x ( 1.0 hematocrit) x 100) /blood concentration = % in plasma The concentration of drug in plasma at intermediate time periods was then calculated from the data obtained for the final sample. The remaining drug solution in the mouth was aspirated and analyzed. The content of para-aminosalicyclic acid in blood and plasma was determined acid. by the method of Way and associate@ for “free” para-amino-salicylie Samples were read in a Bausch and Lomb calorimeter at a wavelength of 540 mp. RESULTS Distilled water
Five hundred milligrams of para-aminosalicyclic acid (PAS) in 1 cc. of distilled water was placed in the floor of the mouth. The distribution of the para-aminosalicylic acid in the blood is illustrated in Fig. 1. Peak absorption was evident 80 minutes after administration, Upon aspiration of the drug remaining in the floor of the mouth, the total amount of drug absorbed was 174 + 12.3 mg. (34.8 per cent). The absorption from the sublingual area was rapid, with
Volume 37 Number 2
Sublingual
I IO TIME
I 20
I 30
I 40
I 50
1 60
1 jr0
I 80
1 90
1 100
of PAS
absorption
1 110
1
1
1
,
120
130
I40
150
323
1 160
Winurss)
Fig. 8. Distribution of PAS in blood at various times after the sublingual administration of 500 mg. in 96 per cent ethyl alcohol. The points at each time interval represent the mean values of six experiments, with the vertical bars representing the associated standard deviation.
measurable blood concentration administration. Ethyl
being achieved as early as 10 minutes
after
alcohol
With the distilled water experiments serving as a base line, various other solutes were tested to determine if this absorption could be altered. In one group of experiments, the para-aminosalicyclic acid was dissolved in 96 per cent alcohol. Again, 1 C.C. of the alcohol solution (500 mg.) was placed sublingually following the cannulation procedures. The distribution of PAS in the blood under this condition is illustrated in Fig. 2. It is apparent that the ethyl alcohol did not significantly alter the absorption or distribution of the PAS. The total amount of drug absorbed was decreased to 26 per cent (131 mg.). The rate of absorption did appear to be affected, with the peak absorption occurring at 40 minutes instead of 80 minutes. Sucrose
In this group of experiments, the PAS was dissolved in a saturated solution of sucrose and administered in a 1 C.C. dose sublingually (500 mg.). The distribution curve is shown in Fig. 3. Again, there was no significant effect upon the distribution or absorption of the PAS (28 per cent absorbed).
324
Oral February,
De Marco and Blonunes
surg. 1974
BLOOD PAS GQ,CC 60
c 5
III1 10
I 20
30
40
SO
I1 60
1 70
80
II 90
11 100
110
120
I
I
!
130
140
150
1 160
T1.W. (54inut.s)
S. Distribution of PAB in blood at various times after the sublingual administration of 500 mg. in saturated sucrosesolution. The points at each time interval represent the mean values of six experiments,with the vertical bars representing the associated standard deviation. Fig.
Vegetable
oil
The experiments were repeated, using vegetable oil as a base. The amount absorbed was decreased to 23.2 per cent, and the peak absorption time occurred in 40 minutes instead of 80 minutes. Venous
occlusion
The jugular veins were tied off bilaterally in order to determine, by indirect means, whether the lymphatic system played any role in the absorption of PAS sublingually. In this manner, any drug that was absorbed would have to have passed through the lymphatic system. The resultant distribution curve is shown in Fig. 4. The total amount of drug absorbed was decreased to 21 per cent (108 mg.). It is assumed that any drug absorbed had to pass through the lymphatic system in order to gain access to the systemic circulation. The results of these five series of experiments are summarized in Table I. The percentage of drug in the plasma was 61.2 per cent + 6.9 per cent for all the experiments. This is in accord with our previous experiments.l DISCUSSION
It has been shown that PAS can be readily absorbed from the sublingual area. Changes in the different solvent bases appear to decrease the absorption slightly.
Volume 37 Number 2
Sublingual
absorption
of PAS
325
BLOOD PASS/H*0 mcgfcc
10
,?D
M
40
50
60
70
80
90
100
110
120
130
140
150
160
TIME (Minutes)
Fig. 4. Distribution of PAS in blood at various times after the sublingual administration of 500 mg. in 1 C.C. distilled water with the jugular veins tied off bilaterally. The points at each time interval represent the mean values of six experiments, with the vertical bars representing the associated standard deviation.
Table I. Effect of various conditions on the sublingual Peak concentrationt Peak time Condition* (?nog./c.c.) (minutes) 80 Water 45.5 + 10.0 40 Vegetable oil 39.0 ? 11.0 40 Ethyl alcohol 40.1 2 7.1 80 Sucrose 42.5 2 9.4 80 Venous occlusion 10.6 + 4.8 "500 mg. in 1.0 C.C.of vehicle. tIn blood. tsignificantly different from water, p < 0.05.
absorption of PAS
Amount remaining in mouth 326.5 k 22.9 384.3 2 35.4 369. 2 29.9 359. 2 22.9 391. ? 13t
Per cent absorbed 34.8 23.2 26.2 28.2 21.8
Both vegetable oil and alcohol changed the peak absorption time from 40 to 80 minutes. Ligation of the jugular veins bilaterally inhibited this absorption, but a significant amount of the drug was still absorbed. It is assumed that the drug had to be absorbed through the lymphatic system. In our earlier studies,’ we had found that ligation of the superior mesenteric vein did not completely inhibit the intestinal absorption of PAS. Under these conditions, 22.7 per cent of the administered dose was still absorbed. It was assumed in that case and in the present study that the material can gain access to the systemic circulation either through the lymphatic system directly or through lymphaticovenous communications made patent by the blood vessel
326
De Marco an.d Blomsnes
Oral February,
Slug. 1974
constriction. Such lymphaticovenous communications have been previously documented by several investigationsG, i Other experiments are obviously indicated in which the lymphatic vessels are cannulated so that the amount of participation of the lymphatic system in this absorption can be accurately assessed. The sublingual absorption of PAS would not appear to be a practical means of administering the drug clinically, since the compound is absorbed well orally (80 per cent orally versus 30 per cent sublingually). However, the foregoing experiment will serve as a model or base line from which to compare the sublingual absorption of other compounds. In such a survey, it would be hoped that sublingual administration would be found to be an effective route for administering some drugs. REFERENCES 1. De Marco,
Thomas J., and Levine, Ruth R.: J. Pharmacol. Exp. Ther. 169: 142-151, 1969. 2. Karmel, J.: Dtsch. Arch. Klin. Med. 12: 466-488, 1873. 3. Katz, M., and Barr, M.: J. Am. Pharm. Assoc. 44: 419-423, 1955. 4. Katz, M., and Barr, M.: J. Am. Pharm. Assoc. 44: 472-476, 1955. Katz, M., and Barr, M.: J. Am. Pharm. Assoc. 44: 476-480, 1955. ii: Roddenberry, H., and Allen, L.: Anat. Rec. 159: 147-158, 1967. Threefoot, 8. A., Kent, W. T., and Hatchett, B. F.: J. Lab. Cl&. Med. 61: 9-22, 1963. L: Walton, R. P.: J. A. M. A. 124: 138, 1944. 9. Way, E. L., Smith, P. K., Howie, D. L., Weiss, R., and Swanson, R.: J. Pharmacol. Exp. Ther. 93: 368-382, 1948. Reprint
requests
to :
Dr. Thomas J. De Marco Case Western Reserve University School of Dentistry 2123 Abington Road Cleveland, Ohio 44106