Interaction of indomethacin and acetylsalicylic acid as shown by the serum concentrations of indomethacin and salicylate

Effects of aspirin and/or salicylate on hydrolysis and glucuronidation of indomethacin in rat erythrocytes and hepatocytes

This study was conducted to explore the mechanism of the pharmacokinetic interaction between aspirin (ASP) and indomethacin (IND) using rat erythrocytes (RBCs) and hepatocytes. ASP was hydrolyzed to salicylic acid (SA) in both the RBCs and hepatocytes. Within RBCs, aspirin and/or salicylate (ASP/SA) increased the concentration of IND, accompanied by a constant hydrolysis of IND. In hepatocytes, a low dose of IND was subjected to glucuronidation rather than hydrolysis, and ASP/SA inhibited both the acylglucuronidation of IND and hydrolysis of IND glucuronide. A high dose of IND underwent hydrolysis with about double the glucuronidation, and ASP/SA decreased the ratio of hydrolysis to glucuronidation, accompanied by a loss of ASP, IND and their metabolites from the medium. Collectively, the results provide metabolic insight into the mechanism of drug-drug interaction between ASP/SA and IND in the hepatocytes and RBCs.

Differential apoptosis by indomethacin in gastric epithelial cells through the constitutive expression of wild-type p53 and/or up-regulation of c-myc

Nonsteroidal anti-inflammatory drug (NSAID)-induced apoptosis is considered to be an important mechanism in the antineoplastic effects and damage produced by the drugs in the gastrointestinal tract. In this study, two different gastric cancer cell lines, MKN28 (mutant-type p53) and AGS (wild-type p53), were compared as to growth inhibition, apoptosis, and cell cycle and apoptosis-related gene expression in response to indomethacin treatment. Cell growth was measured by MTT (3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyl tetrazolium bromide) assay. Apoptosis was characterized by acridine orange staining and DNA fragmentation, and cell cycle kinetics by flow cytometry. The mRNA and protein levels of p53, p21waf1/cip1, and c-myc were determined by Northern and Western blotting. The results showed that indomethacin initiated growth inhibition and apoptosis in both cell lines without cell cycle shifting. AGS cells were more sensitive to growth inhibitory activity and apoptosis of indomethacin than MKN28 cells. In MKN28 cells, the levels of p53, p21waf1/cip1, and c-myc mRNA remained unchanged over the 24-hr treatment with indomethacin, but the p53 protein level was elevated after 4 hr. There was no change in the p21waf1/cip1 and c-myc protein levels in the MKN28 cells. In AGS cells, a progressive increase in c-myc mRNA and protein levels was noted, while p53 and p21waf1/cip1 remained unchanged. It can be concluded that wild-type p53 and/or up-regulation of c-myc is associated with indomethacin-mediated differential apoptosis in gastric epithelial cells.

Pharmacokinetics of postoperative intravenous indomethacin in children

The disposition of indomethacin was studied in children aged one to four years. Indomethacin 0.35 mg/kg was administered as an intravenous infusion during 15 min. Venous blood samples were collected until 24 hr after infusion. Serum indomethacin was determined with gas chromatography. Using a non-linear regression analysis, the individual data were fitted by a two-compartment open mammillary model with central elimination. Calculated pharmacokinetic parameters were (mean +/- SD); alpha half-life 25.2 +/- 11.3 min; beta half-life 366 +/- 295 min; steady-state volume of distribution 0.74 +/- 0.75 l/kg; volume during elimination phase 1.53 +/- 1.27 l/kg; total body clearance 3.2 +/- 1.7 ml/min./kg. Accordingly, with respect to the pharmacokinetics of indomethacin, children seem to mature early, not later than at the age of one year.

Prostaglandins mediate postoperative pain in Falope ring sterilization

To test the hypothesis that prostaglandins mediate the high incidence of postoperative pain in patients undergoing mechanical tubal occlusion, we studied the effect of premedication with a prostaglandin synthetase inhibitor in patients having Falope ring sterilization. Fifty-two women were randomly divided into two groups in which 19 (study group) received a preoperative indomethacin rectal suppository (100 mg) while 33 (control group) received nothing. Postoperative narcotic analgesics were administered as required, and for persistent pain an indomethacin suppository was given in the recovery room. Twenty-four percent of the control group required a postoperative indomethacin suppository because of persisting pain compared to none of the study group (p less than 0.02). These results suggest that prostaglandins mediate, and premedication with a prostaglandin synthetase inhibitor may lessen, postoperative pain in patients having Falope ring sterilization.

Factors determining efficacy of NSAIDs

This article reviews the efficacy of NSAIDs and their pharmacokinetic and pharmacodynamic properties. The assumption that classic pharmacokinetic dose/plasma concentration response relationships can be applied to NSAIDs has tenuous support in the biomedical literature. Comparative efficacy studies, using ASA and indomethacin as the standards for comparison, ignore the fact that the major outcome variables are subjective responses among patients, not among drugs. Comparing inhibition of platelet malonyldialdehyde, synovial drug concentrations, urinary prostaglandin metabolites, and plasma free and total concentration with the clinical outcome provides no guidelines to serve as predictors of response. The individual agents, indomethacin, salicylates, sulindac, piroxicam, and naproxen, illustrate the complexities of NSAID pharmacotherapy. Recent proliferation of newer NSAIDs will not add significantly to the efficacy of these agents in the treatment of pain and inflammatory disease states. However, knowledge of pharmacokinetic population parameters for the individual NSAIDs will increase the likelihood of therapeutic success and diminish the possibilities for adverse reactions.

Indomethacin prevents the long-lasting inhibitory effect of aspirin on human platelet cyclo-oxygenase activity

Aspirin and indomethacin do interact with the same site on cyclo-oxygenase. This suggestion is based on in vitro studies on ram seminal vesicles and in vivo drug interaction studies on rat platelets. The purpose of the present study was to ascertain whether the same interaction also occurred after administration of both drugs to human volunteers. Platelet aggregation induced by sodium arachidonate or by collagen, and formation of platelet MDA and TxB2 were measured before, two and 48 hours after ingestion of either indomethacin (50 mg) or aspirin (500 mg) or of both drugs (30 minutes apart). While the inhibitory effect of indomethacin on these parameters was short lasting, that of aspirin persisted for at least 48 hours. However, when both drugs were given concurrently, the long-lasting effect of aspirin was no longer detectable. Since competition at levels other than platelets was unlikely, this study indicates that indomethacin and aspirin inhibit human platelet cyclo-oxygenase by the same basic mechanism. Acetylation of the enzyme appears to be a secondary mechanism which makes the inhibitory effect of aspirin persistent.

Combination use of nonsteroidal antiinflammatory drugs

Polypharmacy with nonsteroidal antiinflammatory drugs (NSAIDs) is widely practiced despite being condemned by many rheumatologist. Combination use of aspirin with other NSAIDs might be discouraged for three well-documented reasons. First, aspirin reduces the blood levels of many NSAIDs. Second, multiple drugs are antagonistic or at least less than additive in animal models of inflammation. Third, there is no good clinical data to suggest that combination use of NSAIDs is beneficial. Unless new studies become available, NSAIDs should be used one at a time, with supplementary analgesics added on a prn basis.

Piroxicam pharmacokinetics in man: aspirin and antacid interaction studies

Pharmacokinetic studies with piroxicam, a nonsteroidal antiinflammatory agent, have been carried out following the administration of single and multiple oral doses. A plasma half-life of approximately 45 hours is observed, permitting the use of single daily doses in therapy. Enterohepatic recirculation of drug is suggested by the presence of multiple peaks in plasma concentration curves. Piroxicam is highly bound to serum proteins. The absorption and disposition of piroxicam are unaffected by the concomitant administration of aspirin and antiacids. Salicylate plasma levels are similarly unaffected by piroxicam administration.

Comparative pharmacology of a 1:10 combination of indomethacin-sodium salicylate

It has been found that gastrointestinal side-effects of indomethacin could be abolished when administered in combination indomethacin:sodium salicylate (ratio 1:10). In this paper comparative pharmacological data of this combination and its basal compounds are presented. Acute toxicity of the combined preparation was 72 times less in rats than that of indomethacin alone. All therapeutic indexes were markedly increased in the combination of indomethacin-sodium salicylate compared with the separate drug treatments.

Effects of concomitant aspirin administration on the pharmacokinetics of indomethacin in man

Ten healthy volunteers each received single and multiple 50-mg doses of indomethacin orally and a single 25-mg dose of [14C]indomethacin intravenously in the absence of and concomitantly with 1200 mg of aspirin as a single dose and in a chronic t.i.d. regimen. Systematic analysis of the data resulted in the isolation and quantification of aspirin's effects on the absorption, distribution, biotransformation, excretion, enterohepatic circulation, and accumulation of indomethacin. The effects of chronic aspirin were to suppress the renal clearance, to increase the biliary clearance, to decrease the efficiency of gastrointestinal absorption, and to enhance the enterohepatic circulation of indomethacin. On concomitant administration of 1200 mg of aspirin t.i.d., mean plasma levels of indomethacin were depressed by 20% after a single oral dose, by a smaller margin after multiple oral doses, and not at all after a single intravenous dose of indomethacin. The mean plasma concentration of orally administered indomethacin was decreased by 8% when given concurrently with a single 1200 mg dose of aspirin. Concomitant chronic therapeutic dosages of indomethacin had no effect on salicylate accumulation from repetitive doses of aspirin.

Determination of indomethacin in serum by an extractive alkylation technique and gas-liquid chromatography

A method for determining indomethacin in serum has been developed, involving extractive alkylation, in which indomethacin is converted into its ethyl ester, and subsequent gas chromatographic determination of the ester. The method is specific and permits the determination of amounts down to 50 ng/ml in serum. The indomethacin concentration in serum was followed for 24 h after oral and rectal application and the results are compared with those reported in the literature.