Interactions of non-steroidal anti-inflammatory drugs

Nonsteroidal anti-inflammatory drugs in systemic lupus erythematosus

Up to 80% of patients with systemic lupus erythematosus (SLE) are treated with nonsteroidal anti-inflammatory drugs (NSAID) for musculoskeletal symptoms, serositis and headache. This survey reviews the literature on non-selective and selective inhibitors of cyclooxygenases with an emphasis on the efficacy and safety profile reported in SLE patients. No lupus-specific data on gastro-intestinal side effects of NSAID exist. Both non-selective Cox-inhibitors and selective Cox-2 inhibitors induce renal side effects including sodium retention and reduction of the glomerular filtration rate. Lupus nephritis is a risk factor for NSAID-induced acute renal failure, but not for rare idiosyncratic toxic renal reactions to NSAID. In refractory nephrotic syndrome, NSAID have been used successfully. Cutaneous and allergic reactions to NSAID are increased in SLE patients as well as hepatotoxic effects, particularly with high dose aspirin. Whereas a variety of central nervous system side effects of NSAID are probably no more common in SLE patients than in others, aseptic meningitis has been reported more frequently. Ovulation and pregnancy can be adversely affected by Cox-inhibitors. The antiplatelet effect of aspirin and non-selective Cox-inhibitors has a therapeutic potential in patients with the antiphospholipid syndrome (APS). In summary, treatment of SLE with NSAID requires awareness for the increased frequency of some side effects and close monitoring of toxicity.

Nonsteroidal anti-inflammatory drugs in systemic lupus erythematosus

Up to 80% of patients with systemic lupus erythematosus (SLE) are treated with nonsteroidal anti-inflammatory drugs (NSAID) for musculoskeletal symptoms, serositis and headache. This survey reviews the literature on non-selective and selective inhibitors of cyclooxygenases, with an emphasis on the efficacy and safety profile reported in SLE patients. No lupus-specific data on gastro-intestinal side effects of NSAID exist. Both non-selective Cox inhibitors and selective Cox-2 inhibitors induce renal side effects, including sodium retention and reduction of the glomerular filtration rate. Lupus nephritis is a risk factor for NSAID-induced acute renal failure, but not for rare idiosyncratic toxic renal reactions to NSAID. In refractory nephrotic syndrome, NSAID have been used successfully. Cutaneous and allergic reactions to NSAID are increased in SLE patients as well as hepatotoxic effects, particularly with high dose aspirin. Whereas a variety of central nervous system side effects of NSAID are probably no more common in SLE patients than others, aseptic meningitis has been reported more frequently. Ovulation and pregnancy can be adversely affected by Cox inhibitors. The antiplatelet effect of aspirin and non-selective Cox inhibitors has a therapeutic potential in patients with antiphospholipid syndrome (APS). In summary, treatment of SLE with NSAID requires awareness for the increased frequency of some side effects and close monitoring of toxicity.

Potentiation of oral anticoagulation and hemarthrosis associated with nabumetone

Concomitant therapy with warfarin and nonsteroidal antiinflammatory drugs (NSAIDs) is of concern due to the potential for increased bleeding. Nonsteroidal antiinflammatory drugs may alter patient response to warfarin by pharmacodynamic or pharmacokinetic interactions. A man receiving long-term, stable warfarin therapy experienced a significant increase in international normalized ratio 1 week after nabumetone was added to his regimen. Despite prompt reduction of the warfarin dosage, he experienced hemarthrosis of his right knee. Previous reports suggested lack of interaction between nabumetone and warfarin. Caution and close monitoring are advisable when the two agents are administered concomitantly.

Interaction of meloxicam with cimetidine, Maalox, or aspirin

Meloxicam is a new enol carboxamide nonsteroidal antiinflammatory drug (NSAID). Preclinical studies have indicated that it possesses a high antiinflammatory potency and a low ulcerogenic potency. This open, randomized, crossover study was conducted to examine the effects of aspirin, the antacid Maalox (Rhone-Poulenc Rorer, Cologne, Germany), and cimetidine on the pharmacokinetics and bioavailability of a single oral dose of meloxicam 30 mg in healthy male volunteers. Plasma concentrations of meloxicam were determined and subjected to noncompartmental pharmacokinetic analysis. Meloxicam was well tolerated, and concomitant treatment with cimetidine or Maalox had little or no effect on the plasma concentration-time curves, maximum plasma concentration (Cmax), or the area under the plasma concentration-time curve (AUC0-infinity) of meloxicam. Concurrent treatment with aspirin increased plasma concentrations of meloxicam, increasing Cmax by approximately 25% and AUC0-infinity by 10%. These differences were not considered to be clinically relevant, and no adjustments of meloxicam dose should be required with coadministration of aspirin, Maalox, or cimetidine.

Adverse interactions between warfarin and nonsteroidal antiinflammatory drugs: mechanisms, clinical significance, and avoidance

OBJECTIVE

To review the mechanisms and clinical significance of adverse interactions between warfarin and nonsteroidal anti-inflammatory drugs (NSAIDs) and discuss how these interactions can be avoided.

DATA SOURCES

Previous studies of interactions between warfarin and NSAIDs or reports of adverse interactions were identified from a MEDLINE search (1976 to present) and from the reference lists of pertinent articles.

STUDY SELECTION AND DATA EXTRACTION

All articles were considered for inclusion in the review. Pertinent information was selected for discussion.

DATA SYNTHESIS

All NSAIDs can prolong bleeding time by inhibiting platelet function. High-dose aspirin has a direct hypoprothrombinemic effect. Phenylbutazone and its analogs enhance the hypoprothrombinemic effect of warfarin through a pharmacokinetic interaction by inhibiting the hepatic metabolism of warfarin. Mefenamic acid also enhances the anticoagulant effect of warfarin, but the mechanism is not known. The clinical relevance of protein binding displacement in the interaction between warfarin and NSAIDs has been overstated, although a significant one may be more likely in the presence of high concentrations of NSAIDs in patients with slow elimination of warfarin (e.g., those with severe heart failure or impaired liver function). NSAIDs can induce gastrointestinal bleeding, which is likely to be more severe if warfarin is also given.

CONCLUSIONS

The combined use of warfarin and NSAIDs is generally discouraged because of the increased risk of bleeding in these patients. In patients receiving warfarin who also require NSAIDs, phenylbutazone and its analogs, high-dose aspirin, mefenamic acid, excessive use of topical methyl salicylate, and NSAIDs that are associated with a higher risk of bleeding peptic ulcers should be avoided. Patients should be closely monitored for anticoagulant control and bleeding complications during the combined use of warfarin and NSAIDs.

Non-steroidal anti-inflammatory drugs

The elderly are at higher risk of adverse reactions from non-steroidal anti-inflammatory drugs (NSAIDs), including those due to drug interactions, than younger people. Before prescribing oral NSAIDs in the elderly, the clinician should consider other forms of therapy and topical NSAIDs. When an oral NSAID is used, the dose should be minimised and the need for treatment reviewed periodically to reduce duration of therapy. NSAIDs with a high risk of toxicity (such as phenylbutazone, salicylates, piroxicam and indomethacin) should be avoided in the elderly.

Pharmacokinetics of etodolac enantiomers in the rat after administration of phenobarbital or cimetidine

The influences of phenobarbital and cimetidine on the pharmacokinetics of etodolac enantiomers were studied in male Sprague-Dawley rats. Phenobarbital caused significant reductions in the AUC of both the active S-enantiomer (24%) and the inactive R-enantiomer of etodolac (26%), and an increase in the urinary excretion of glucuronidated S-etodolac. In bile duct-cannulated rats the initial biliary recoveries of the acyl-glucuronidated etodolac enantiomers were not affected by phenobarbital. In vitro, phenobarbital caused no changes in the hepatic microsomal net glucuronidation of etodolac enantiomers after phenobarbital, although it did result in significant increases in the apparent oxidative metabolism of both enantiomers. Therefore, phenobarbital seems to cause an enhanced CL of etodolac by induction of hepatic non-conjugative metabolism. Cimetidine had no discernible effect on the pharmacokinetics of etodolac enantiomers.

The problems and pitfalls of NSAID therapy in the elderly (Part II)

The elderly are most susceptible to pharmacokinetic drug interactions between various NSAIDs and anticoagulants, sulphonylurea hypoglycaemic agents, certain anticonvulsants, methotrexate, digoxin, aminoglycosides and lithium. Pharmacodynamic interactions between some NSAIDs and antihypertensive drugs, anticoagulants, sulphonylurea agents and other NSAIDs are also potentially significant in the elderly. Despite the finding that mean therapeutic responses of large groups of patients have been generally equivalent for the wide range of NSAIDs studied thus far, it is also apparent that marked variability exists in the response of individual patients to different NSAIDs. Subsequent dosage increments may predispose 'nonresponders' and some less sensitive 'responders' to toxicity from NSAIDs. This interindividual variability in response to NSAIDs may be contributed to by the differing physicochemical properties of NSAIDs, physician prescribing habits and patient expectations, variations in NSAID pharmacokinetics, and the differing effects of NSAIDs other than their common ability to inhibit prostaglandin synthesis. The principles for drug prescribing in the elderly are no different from those that should be applied to the prescribing of medication in any patient. The clinician should strive to make a diagnosis and should avoid treating symptoms in isolation. Critical assessment of the indication for prescribing NSAID therapy must include consideration of the available effective and safe alternatives. If an NSAID is commenced the lowest effective dose should be the desired goal, but after an appropriate trial it is acceptable clinical practice to employ an alternative NSAID. There is no justification for combination NSAID therapy. The progress of each patient must be carefully monitored, particularly during the first few months of treatment, while periodic review of the ongoing need for the NSAID is essential.

The effects of sulindac and diclofenac in essential hypertension controlled by treatment with a beta blocker and/or diuretic

A placebo-controlled, double blind crossover study of the non-steroidal anti-inflammatory drugs (NSAIDs) sulindac and diclofenac was conducted in 16 patients with essential hypertension that was controlled by treatment with a beta blocker, a diuretic or co-administration of both. In 4 cases, another antihypertensive agent (prazosin or verapamil) was also co-administered. In every patient, plasma creatinine concentration was less than 0.14 mmol/l (normal range 0.07-0.12 mmol/l). Sulindac and diclofenac were each given for 7 weeks. Diclofenac caused a decrease of borderline significance in plasma aldosterone concentration. Neither NSAID altered the mean values for systolic or diastolic blood pressure, body weight, plasma electrolyte concentrations, urate clearance, creatinine clearance or plasma renin activity. However, rises in plasma creatinine concentration and falls in creatinine clearance occurred during NSAID therapy in three individual subjects. No significant differences were observed in this study between the effects on renal function or blood pressure of sulindac and diclofenac, both of which appear not to interfere with the antihypertensive actions of beta blockers and diuretics.