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Testing for the gastro-intestinal irritancy of aspirin and indomethacin
Testing for the Gastro-Intestinal lndomethacin
R. GOBURDHUN,
lrritancy of Aspirin and
K. GULREZ, H. HARUNA, AND G. B. WEST
lesions produced in rats in 4 hr by aspirin or indomethacin form a reasonable basis for testing antiulcer activity of new drugs. Two oral doses of indomethacin 24 hr apart significantly lower the tensile strength of the small intestine in 4 hr. Aspirin, on the other hand, does not exert this effect. A single intraperitoneal dose of indomethacin produces severe gastric lesions in 4 hr without altering the intestinal tensile strength. Aspirin, on the other hand, is ineffective by this route on both stomach and intestine. Sodium salicylate, like copper salicylate, almost completely prevents gastric lesions produced by either aspirin or by indomethacin in 4 hr. lndomethacin and copper salicylate, but not aspirin and sodium salicylate, are irritant when injected subcutaneously into rat hind paws.
Gastric
Key Words:
Gastric lesions; Salicylates; lndomethacin;
Copper complexes.
INTRODUCTION Castro-intestinal side-effects of nonsteroidal anti-inflammatory agents in the form of microhemorrhages in man and animals are well documented. However, many factors in animal tests influence the extent of the damage. For example, the strain of rat, sex, body-weight, length of starvation, duration of drug action, and the suspending agent for the drug all play a role in identifying a satisfactory method for detecting ulcerogenic activity. The method of scoring the degree of gastric damage is also a major problem. Recently some new anti-inflammatory agents have been shown to cause no gastric lesions but to be highly irritating outside the stomach. Consequently, there is a need for tests for gastro-intestinal irritancy and for edema production in subcutaneous areas such as the rat paw. Using simple techniques, we have investigated some of the factors involved in such tests and report here methods we have found to produce consistent results so that new ulcerogenic and antiulcer compounds can be tested and evaluated. METHODS Food was withheld from groups of eight Tuck Wistar rats (150-200 g), and after 24 hr compounds suspended in 0.1% Tween 80 were administered orally. The rats were then killed at various intervals, their stomachs removed, washed with saline, Received January 16,1978; accepted February 15,1978. From the Department of Paramedical Sciences, North East London Polytechnic, London, U.K. Address reprint requests to: Dr. R. Goburdhun, Department of Paramedical Sciences, North East London Polytechnic, Romford Road, London El5 4L2, U.K.
109 @Else&r
North-Holland,
Inc., 1978, Journal of Pharmacological Methods
1, 109-114 (1978)
0160-5402/7lv~l-01
09/$01.75
110
R. Goburdhun
et al.
and opened along the lesser curvature. Lesion production was scored by measuring the length of each lesion under a threefold magnifier and summating the values to give a total lesion index (in millimeters) for each rat. The mean scores (2 SEM) for each group were then calculated (maximum score of 40 per rat) and the results were analyzed using the Students t-test. Control groups of rats were given doses of the suspending vehicle and similarly evaluated. The tensile strength of the intestinal wall was measured by two methods: In the first, the duodenum was ligated at one end and a polyethylene cannula connected to a Condon mercury manometer and a hand bulb inflator was inserted into the other end. Pressure was slowly increased until a bubble appeared in the saline at 37” which was contained in a beaker into which the duodenum was immersed, The pressure, in mm Hg, required to rupture a unit length (1 mm) of intestinal wall was calculated and used as one measure of intestinal tensile strength. Thus, for a 20 mm length of intestine requiring 200 mm Hg pressure for rupture, the value was taken as IO units. In the second method, the duodenum was ligated at both ends and saline at 37” was injected slowly into the segment with a syringe until the intestinal wall burst. The volume, in ml, required to rupture a unit length (1 mm) of intestinal wall was calculated and 500 times this volume was used as the other measurement of intestinal tensile strength. Thus, for a 20-mm length of intestine requiring 0.4 ml saline for rupture, the value was 10 units. The means of the values obtained with the two methods in each group were calculated (intact intestine score normally about 25 units) and the results were analyzed using the Student’s t-test. In some experiments two doses of drug were given: the first at the time of food withdrawal and the second 24 hr later. In other experiments, drugs were given by the intraperitoneal route to fasted animals. Some rats also received the simultaneous oral administration of agonist and antagonist (sodium salicylate, copper salicylate). To determine irritancy outside the gastro-intestinal tract, the drugs were injected subcutaneously into one hind paw of rats and the paw swelling measured every 15 min for 2 hr in a mercury displacement differential volume meter. The other hind paw received 0.1 ml of Tween 80 (0.1%) and served as control. The paws were always immersed into the mercury to reference marks made over the lateral malleolus bone of each foot. The difference between the readings of the two foot volumes was used as a measure of edema. Percentage changes were then calculated and results analyzed as before. RESULTS Effect of Time on lesion
Production
The results shown in Fig. 1 illustrate lesion production over 4 hr when rats were given orally either 200 mg kg-’ aspirin or 20 mg kg-’ indomethacin. At these dose levels, indomethacin exerted a much greater effect on the gastric mucosa than did aspirin, particularly at 4 hr. The standard procedure for subsequent experiments involving gastric irritation was to use a 4 hr test period. Throughout these experiments, the tensile strength of the duodenum remained constant at 21-23 units. The suspending agent for the drugs (Tween 80) exerted no effect on the gastric mucosa or on the duodenum.
Aspirin and lndomethacin
Gastric Lesions
20J P IO-
0
4 4
' Time (h) 2
FIGURE 1. Production of gastric lesions (lesion index in mm+SEM) in rats by oral doses of 200 mg kg-’ aspirin (0) and of 20 mg kg-’ indomethacin (0) at given times after drug.
Effect of Divided
Doses of Drug on lesion
Production
Lesion production at 4 hr was next studied in rats given two oral doses of drug 24 hr apart, as Ezer et al. (1976) had reported that indomethacin showed a delayed effect on the intestinal wall. The results are recorded in Table 1 where values using single doses are shown for comparison. Whereas the two dose schedule did not alter the effect of aspirin, the two doses of indomethacin not only increased the gastric lesion production but also significantly lowered the tensile strength of the duodenum. Two corresponding doses of suspending agent were without effect. Effect of Route of Injection
on lesion
Production
Effects obtained by the oral route were next compared with those obtained intraperitoneally. It was apparent that, whereas aspirin was ineffective in producing gastric irritation on injection, indomethacin produced gross gastric lesions at 4 hr
TABLE 1 Comparison of Effects of Single and Divided Oral Doses of Aspirin and lndomethacin on Gastric lesion Production (mm f SEM) and Intestinal Tensile Strength (Units) in Rats 4 hr after Treatment INTESTINAL DRUG Aspirin
lndomethacin
a Significant at P < 0.05 10 mg kg-l).
DOSE (MC KC-‘)
GASTRIC
LESION
TENSILE
STRENGTH
200
8.0 ? 2.7
19 2 3
2 x 200
a.7 2 3.1
20 2 2
400
10.6 -=I2.5
IQ 2 x 10 20
13.2 f 2.0 18.5 + 2.1” 19.1 ?z 5.1
16 f 1 19* 3 10 2 2” 18 f 2
(when compared with values after a single dose of
111
112
R. Goburdhun
et al.
40
0
01 01 200 400 Asbirin
Indometkacin
FIGURE 2. Production of gastric lesions (lesion index in mmltSEM) in rats by oral (0) and intraperitoneal (I) doses of aspirin (200 and 400 mg kg-l) and of indomethacin (10 and 20 mg kg-‘) 4 hr after drug treatment.
when single doses of 20 mg kg-’ were injected (Fig. 2). However, the tensile strength of the duodenum again remained unchanged throughout. The suspending agent alone was without effect on intraperitoneal injection. Effect of Antagonists on lesion
Production
Mixing sodium salicylate with aspirin or indomethacin greatly reduced gastric lesion production (Table Z), thereby confirming the observations of Ezer et al, (1976). Orally administered doses of 150 mg kg-’ of sodium silicylate, which had no action per se almost completely inhibited the effects, whereas half this dose produced about a 40% reduction in response. Copper salicylate was more effective than sodium salicylate, doses of 15 mg kg-’ exerting significant inhibition of both aspirin and indomethacin effects. Duodenal tensile strength again remained unchanged throughout (19-22 units). lrritancy in the Paw Drugs were injected into the hind paw of rats to determine irritancy outside the gastric mucosa and increases in foot volume were recorded over 2 hr. Peak increases, usually at 30 min, are summarized in Table 3, all solutions being adjusted to pH 6.0-7.0 before injection. Only the higher doses of indomethacin and copper salicylate produced significant swelling, indicating irritant action.
Aspirin and lndomethacin
Gastric Lesions
TABLE 2 Effect of Oral Antagonists on Gastric lesion Production (mm f SEM) by Oral Aspirin (400 mg kg-l) and lndomethacin (20 mg kg-l) in Rats 4 hr after Treatment DOSE AGONIST
ANTAGONIST
Aspirin
None Sodium salicylate Copper salicylate
lndomethacin
None Sodium salicylate Copper salicylate
(MC KG-‘)
75 150 7.5 15 75 150 7.5 15
PERCENTAGE
GASTRIC
lNHl6iTi0~
LESION
-
10.5 2 2.7 6.6 k 3.0
37 95” 25 63” -
0.2 ” O.lD 7.5 + 1.8 2.8 +- 3.3” 18.9 2 5.0 11.1 + 4.3
41 90” 36 49”
1.6 k 0.2” 12.2 + 3.4 6.2 k 2.0”
’ Significant at P < 0.05 (when compared with values without antagonist).
DISCUSSION The present results show that aspirin and indomethacin irritate the gastric mucosa and produce lesions but, whereas indomethacin is effective both orally and intraperitoneally, aspirin only exerts its effect orally. The detection of gastric damage has been achieved in simple tests using one strain of Wistar rats after overnight starvation and 4 hr of drug treatment. In the literature, this latter factor has varied: 1 hr for aspirin and 4 hr for indomethacin in one case (Boyle et al., 1976); 2 hr for both drugs (Rainsford and Whitehouse, 1976); 3 hr for other anti-inflammatory drugs such as benoxaprofen (Cashin et al., 1977); and 4 hr for aspirin and indomethacin (Ezer et al., 1976). The present authors found the 4 hr test for both drugs after oral dosage to be satisfactory, producing adequate lesions in the stomach wall but not lowering duodenal tensile strength. To achieve such a lowering, it was
TABLE 3 Effect of Agonists and Antagonists of Gastric lesion Production in Rats on the Foot Volume after Subcutaneous Injection EQUIVALENT DRUG Aspirin
DOSE
ORAL DOSE
FOOT VOLUME
(MC/PAW)
(MC KG-‘)
(% INCREASE)
4 8
lndomethacin
0.2 0.4
Sodium
salicylate
1.5
Copper
salicylate
0.15
3 0.3
200 400 10 20 75 150 7.5 15
4rt_2 17 + 6 162 3 36 f 5’ 422 6-c2 16 f 5 56 f 6’
Q Significant at P < 0.05 (when compared with values for Tween
80 alone).
113
114
R. Goburdhun et al.
necessary to give the two divided doses of indomethacin (Ezer et al., 1976). Aspirin did not alter the tensile strength even when it was administered orally in divided doses or intraperitoneally as a single dose (when indomethacin was an effective irritant to the gastric mucosa). The 4 hr test forms a reasonable basis for testing antiulcer activity of new drugs. Ezer et al. (1976) reported that sodium salicylate antagonized the lesion sideeffects of aspirin and indomethacin without modifying the main effects of the compounds and we have confirmed this and extended it to copper salicylate, though the latter compound is more effective against aspirin during the 4 hr of the test. It is possible that the aspirin-like drugs separately induce ulcers, as stated by Ezer et al. (1976), by unbalancing prostaglandin equilibrium, but when mixed with sodium or copper salicylate the combined disturbances in the equilibrium are not strong enough to cause damage in the gut wall. Finally, irritancy outside the stomach may be an important side-effect and so it is important to determine this by direct application to a peripheral site (rat paw). However, indomethacin was found to be an irritant by this route, although it is a clinically effective anti-inflammatory agent, inferring that this action may not be so worrying in a powerful anti-arthritic drug.
REFERENCES Boyle E, Freeman PC, Gondie AC, Mangan ER, Thomson M (1976) The role of copper in preventing gastrointestinal damage by acidic antiinflammatory drugs. / Pharm Pharmacol28: 865868.
Ezer E, Palose E, Hajos, Gy, Szporny L (1976) Antagonism of the gastro-intestinal ulcerogenic effect of some non-steroidal anti-inflammatory agents by sodium salicylate. J Pharm Pharmacol 28: 655-656.
Cashin CH, Dawson W, Kitchen EA (1977) The pharmacology of benoxaprofen, a new compound with anti-inflammatory activity apparently unrelated to inhibition of prostaglanding synthesis. J Pharm Pharmacol29: 330-336.
Rainsford KD, Whitehouse MW (1976) Gastric mucus effusion elicited by oral copper compounds. Experientia 32: 1172.
R. GOBURDHUN,
lrritancy of Aspirin and
K. GULREZ, H. HARUNA, AND G. B. WEST
lesions produced in rats in 4 hr by aspirin or indomethacin form a reasonable basis for testing antiulcer activity of new drugs. Two oral doses of indomethacin 24 hr apart significantly lower the tensile strength of the small intestine in 4 hr. Aspirin, on the other hand, does not exert this effect. A single intraperitoneal dose of indomethacin produces severe gastric lesions in 4 hr without altering the intestinal tensile strength. Aspirin, on the other hand, is ineffective by this route on both stomach and intestine. Sodium salicylate, like copper salicylate, almost completely prevents gastric lesions produced by either aspirin or by indomethacin in 4 hr. lndomethacin and copper salicylate, but not aspirin and sodium salicylate, are irritant when injected subcutaneously into rat hind paws.
Gastric
Key Words:
Gastric lesions; Salicylates; lndomethacin;
Copper complexes.
INTRODUCTION Castro-intestinal side-effects of nonsteroidal anti-inflammatory agents in the form of microhemorrhages in man and animals are well documented. However, many factors in animal tests influence the extent of the damage. For example, the strain of rat, sex, body-weight, length of starvation, duration of drug action, and the suspending agent for the drug all play a role in identifying a satisfactory method for detecting ulcerogenic activity. The method of scoring the degree of gastric damage is also a major problem. Recently some new anti-inflammatory agents have been shown to cause no gastric lesions but to be highly irritating outside the stomach. Consequently, there is a need for tests for gastro-intestinal irritancy and for edema production in subcutaneous areas such as the rat paw. Using simple techniques, we have investigated some of the factors involved in such tests and report here methods we have found to produce consistent results so that new ulcerogenic and antiulcer compounds can be tested and evaluated. METHODS Food was withheld from groups of eight Tuck Wistar rats (150-200 g), and after 24 hr compounds suspended in 0.1% Tween 80 were administered orally. The rats were then killed at various intervals, their stomachs removed, washed with saline, Received January 16,1978; accepted February 15,1978. From the Department of Paramedical Sciences, North East London Polytechnic, London, U.K. Address reprint requests to: Dr. R. Goburdhun, Department of Paramedical Sciences, North East London Polytechnic, Romford Road, London El5 4L2, U.K.
109 @Else&r
North-Holland,
Inc., 1978, Journal of Pharmacological Methods
1, 109-114 (1978)
0160-5402/7lv~l-01
09/$01.75
110
R. Goburdhun
et al.
and opened along the lesser curvature. Lesion production was scored by measuring the length of each lesion under a threefold magnifier and summating the values to give a total lesion index (in millimeters) for each rat. The mean scores (2 SEM) for each group were then calculated (maximum score of 40 per rat) and the results were analyzed using the Students t-test. Control groups of rats were given doses of the suspending vehicle and similarly evaluated. The tensile strength of the intestinal wall was measured by two methods: In the first, the duodenum was ligated at one end and a polyethylene cannula connected to a Condon mercury manometer and a hand bulb inflator was inserted into the other end. Pressure was slowly increased until a bubble appeared in the saline at 37” which was contained in a beaker into which the duodenum was immersed, The pressure, in mm Hg, required to rupture a unit length (1 mm) of intestinal wall was calculated and used as one measure of intestinal tensile strength. Thus, for a 20 mm length of intestine requiring 200 mm Hg pressure for rupture, the value was taken as IO units. In the second method, the duodenum was ligated at both ends and saline at 37” was injected slowly into the segment with a syringe until the intestinal wall burst. The volume, in ml, required to rupture a unit length (1 mm) of intestinal wall was calculated and 500 times this volume was used as the other measurement of intestinal tensile strength. Thus, for a 20-mm length of intestine requiring 0.4 ml saline for rupture, the value was 10 units. The means of the values obtained with the two methods in each group were calculated (intact intestine score normally about 25 units) and the results were analyzed using the Student’s t-test. In some experiments two doses of drug were given: the first at the time of food withdrawal and the second 24 hr later. In other experiments, drugs were given by the intraperitoneal route to fasted animals. Some rats also received the simultaneous oral administration of agonist and antagonist (sodium salicylate, copper salicylate). To determine irritancy outside the gastro-intestinal tract, the drugs were injected subcutaneously into one hind paw of rats and the paw swelling measured every 15 min for 2 hr in a mercury displacement differential volume meter. The other hind paw received 0.1 ml of Tween 80 (0.1%) and served as control. The paws were always immersed into the mercury to reference marks made over the lateral malleolus bone of each foot. The difference between the readings of the two foot volumes was used as a measure of edema. Percentage changes were then calculated and results analyzed as before. RESULTS Effect of Time on lesion
Production
The results shown in Fig. 1 illustrate lesion production over 4 hr when rats were given orally either 200 mg kg-’ aspirin or 20 mg kg-’ indomethacin. At these dose levels, indomethacin exerted a much greater effect on the gastric mucosa than did aspirin, particularly at 4 hr. The standard procedure for subsequent experiments involving gastric irritation was to use a 4 hr test period. Throughout these experiments, the tensile strength of the duodenum remained constant at 21-23 units. The suspending agent for the drugs (Tween 80) exerted no effect on the gastric mucosa or on the duodenum.
Aspirin and lndomethacin
Gastric Lesions
20J P IO-
0
4 4
' Time (h) 2
FIGURE 1. Production of gastric lesions (lesion index in mm+SEM) in rats by oral doses of 200 mg kg-’ aspirin (0) and of 20 mg kg-’ indomethacin (0) at given times after drug.
Effect of Divided
Doses of Drug on lesion
Production
Lesion production at 4 hr was next studied in rats given two oral doses of drug 24 hr apart, as Ezer et al. (1976) had reported that indomethacin showed a delayed effect on the intestinal wall. The results are recorded in Table 1 where values using single doses are shown for comparison. Whereas the two dose schedule did not alter the effect of aspirin, the two doses of indomethacin not only increased the gastric lesion production but also significantly lowered the tensile strength of the duodenum. Two corresponding doses of suspending agent were without effect. Effect of Route of Injection
on lesion
Production
Effects obtained by the oral route were next compared with those obtained intraperitoneally. It was apparent that, whereas aspirin was ineffective in producing gastric irritation on injection, indomethacin produced gross gastric lesions at 4 hr
TABLE 1 Comparison of Effects of Single and Divided Oral Doses of Aspirin and lndomethacin on Gastric lesion Production (mm f SEM) and Intestinal Tensile Strength (Units) in Rats 4 hr after Treatment INTESTINAL DRUG Aspirin
lndomethacin
a Significant at P < 0.05 10 mg kg-l).
DOSE (MC KC-‘)
GASTRIC
LESION
TENSILE
STRENGTH
200
8.0 ? 2.7
19 2 3
2 x 200
a.7 2 3.1
20 2 2
400
10.6 -=I2.5
IQ 2 x 10 20
13.2 f 2.0 18.5 + 2.1” 19.1 ?z 5.1
16 f 1 19* 3 10 2 2” 18 f 2
(when compared with values after a single dose of
111
112
R. Goburdhun
et al.
40
0
01 01 200 400 Asbirin
Indometkacin
FIGURE 2. Production of gastric lesions (lesion index in mmltSEM) in rats by oral (0) and intraperitoneal (I) doses of aspirin (200 and 400 mg kg-l) and of indomethacin (10 and 20 mg kg-‘) 4 hr after drug treatment.
when single doses of 20 mg kg-’ were injected (Fig. 2). However, the tensile strength of the duodenum again remained unchanged throughout. The suspending agent alone was without effect on intraperitoneal injection. Effect of Antagonists on lesion
Production
Mixing sodium salicylate with aspirin or indomethacin greatly reduced gastric lesion production (Table Z), thereby confirming the observations of Ezer et al, (1976). Orally administered doses of 150 mg kg-’ of sodium silicylate, which had no action per se almost completely inhibited the effects, whereas half this dose produced about a 40% reduction in response. Copper salicylate was more effective than sodium salicylate, doses of 15 mg kg-’ exerting significant inhibition of both aspirin and indomethacin effects. Duodenal tensile strength again remained unchanged throughout (19-22 units). lrritancy in the Paw Drugs were injected into the hind paw of rats to determine irritancy outside the gastric mucosa and increases in foot volume were recorded over 2 hr. Peak increases, usually at 30 min, are summarized in Table 3, all solutions being adjusted to pH 6.0-7.0 before injection. Only the higher doses of indomethacin and copper salicylate produced significant swelling, indicating irritant action.
Aspirin and lndomethacin
Gastric Lesions
TABLE 2 Effect of Oral Antagonists on Gastric lesion Production (mm f SEM) by Oral Aspirin (400 mg kg-l) and lndomethacin (20 mg kg-l) in Rats 4 hr after Treatment DOSE AGONIST
ANTAGONIST
Aspirin
None Sodium salicylate Copper salicylate
lndomethacin
None Sodium salicylate Copper salicylate
(MC KG-‘)
75 150 7.5 15 75 150 7.5 15
PERCENTAGE
GASTRIC
lNHl6iTi0~
LESION
-
10.5 2 2.7 6.6 k 3.0
37 95” 25 63” -
0.2 ” O.lD 7.5 + 1.8 2.8 +- 3.3” 18.9 2 5.0 11.1 + 4.3
41 90” 36 49”
1.6 k 0.2” 12.2 + 3.4 6.2 k 2.0”
’ Significant at P < 0.05 (when compared with values without antagonist).
DISCUSSION The present results show that aspirin and indomethacin irritate the gastric mucosa and produce lesions but, whereas indomethacin is effective both orally and intraperitoneally, aspirin only exerts its effect orally. The detection of gastric damage has been achieved in simple tests using one strain of Wistar rats after overnight starvation and 4 hr of drug treatment. In the literature, this latter factor has varied: 1 hr for aspirin and 4 hr for indomethacin in one case (Boyle et al., 1976); 2 hr for both drugs (Rainsford and Whitehouse, 1976); 3 hr for other anti-inflammatory drugs such as benoxaprofen (Cashin et al., 1977); and 4 hr for aspirin and indomethacin (Ezer et al., 1976). The present authors found the 4 hr test for both drugs after oral dosage to be satisfactory, producing adequate lesions in the stomach wall but not lowering duodenal tensile strength. To achieve such a lowering, it was
TABLE 3 Effect of Agonists and Antagonists of Gastric lesion Production in Rats on the Foot Volume after Subcutaneous Injection EQUIVALENT DRUG Aspirin
DOSE
ORAL DOSE
FOOT VOLUME
(MC/PAW)
(MC KG-‘)
(% INCREASE)
4 8
lndomethacin
0.2 0.4
Sodium
salicylate
1.5
Copper
salicylate
0.15
3 0.3
200 400 10 20 75 150 7.5 15
4rt_2 17 + 6 162 3 36 f 5’ 422 6-c2 16 f 5 56 f 6’
Q Significant at P < 0.05 (when compared with values for Tween
80 alone).
113
114
R. Goburdhun et al.
necessary to give the two divided doses of indomethacin (Ezer et al., 1976). Aspirin did not alter the tensile strength even when it was administered orally in divided doses or intraperitoneally as a single dose (when indomethacin was an effective irritant to the gastric mucosa). The 4 hr test forms a reasonable basis for testing antiulcer activity of new drugs. Ezer et al. (1976) reported that sodium salicylate antagonized the lesion sideeffects of aspirin and indomethacin without modifying the main effects of the compounds and we have confirmed this and extended it to copper salicylate, though the latter compound is more effective against aspirin during the 4 hr of the test. It is possible that the aspirin-like drugs separately induce ulcers, as stated by Ezer et al. (1976), by unbalancing prostaglandin equilibrium, but when mixed with sodium or copper salicylate the combined disturbances in the equilibrium are not strong enough to cause damage in the gut wall. Finally, irritancy outside the stomach may be an important side-effect and so it is important to determine this by direct application to a peripheral site (rat paw). However, indomethacin was found to be an irritant by this route, although it is a clinically effective anti-inflammatory agent, inferring that this action may not be so worrying in a powerful anti-arthritic drug.
REFERENCES Boyle E, Freeman PC, Gondie AC, Mangan ER, Thomson M (1976) The role of copper in preventing gastrointestinal damage by acidic antiinflammatory drugs. / Pharm Pharmacol28: 865868.
Ezer E, Palose E, Hajos, Gy, Szporny L (1976) Antagonism of the gastro-intestinal ulcerogenic effect of some non-steroidal anti-inflammatory agents by sodium salicylate. J Pharm Pharmacol 28: 655-656.
Cashin CH, Dawson W, Kitchen EA (1977) The pharmacology of benoxaprofen, a new compound with anti-inflammatory activity apparently unrelated to inhibition of prostaglanding synthesis. J Pharm Pharmacol29: 330-336.
Rainsford KD, Whitehouse MW (1976) Gastric mucus effusion elicited by oral copper compounds. Experientia 32: 1172.