Single and multiple dose pharmacokinetics of enteric coated ketoprofen: effect of cimetidine

Topical ketoprofen patch

Although oral nonsteroidal anti-inflammatory drugs (NSAIDs) are effective in the treatment of a variety of acute and chronic pain conditions, their use may be associated with serious systemic adverse effects, particularly gastrointestinal disorders. In order to minimise the incidence of systemic events related to such agents, topical NSAIDs have been developed. Topical NSAIDs, applied as gels, creams or sprays, penetrate the skin, subcutaneous fatty tissue and muscle in amounts that are sufficient to exert a therapeutic effect on peripheral and central mechanisms in the absence of high plasma concentrations. Data indicate that topical NSAIDs are effective at relieving pain in a number of acute and chronic pain indications. This review article discusses the pharmacokinetics, efficacy and tolerability of a new formulation of ketoprofen available as a topical patch. The topical patch containing ketoprofen 100mg as the active principle has been developed using a novel delivery system that dispenses therapeutic doses of the drug directly to the site of injury. Pharmacokinetic data indicate that although plasma levels of ketoprofen are higher when the drug is administered as a patch versus a gel, the total systemic bioavailability of ketoprofen 100 mg administered via a patch is no more than 10% of that reported for ketoprofen 100 mg administered orally. Because the patch facilitates ketoprofen delivery over a 24-hour period, the drug remains continually present in the tissue subjacent to the site of application. High tissue but low plasma ketoprofen concentrations mean that while tissue concentrations are high enough to exert a therapeutic effect, plasma concentrations remain low enough to not result in systemic adverse events caused by elevated serum NSAID levels. Phase III clinical trials in patients with non-articular rheumatism and traumatic painful soft tissue injuries showed that the topical ketoprofen patch was significantly more effective than placebo at reducing pain during daily activities and spontaneous pain after 7 days' treatment. Moreover, the topical ketoprofen patch was well tolerated; adverse events were primarily cutaneous in nature and occurred in a similar number of ketoprofen and placebo recipients suggesting that these events were related to the patch itself rather than the active ingredient. The incidence of gastrointestinal adverse events was low (<8% of all patients), and occurred in a similar proportion of patients receiving ketoprofen and placebo. Thus, the topical ketoprofen patch appears to be a simple, effective and safe therapeutic option for the treatment of local painful inflammation.

Pharmacokinetic drug interactions with anti-ulcer drugs

The safety profile of any pharmacological agent is defined on the basis of its toxicity, tolerability and potential for pharmacokinetic and/or pharmacodynamic interactions with other compounds, which may belong to the same or to a different pharmacological class. Drug-drug interactions are important in clinical practice because short and long term therapeutic regimens frequently require coadministration of different drugs. The pharmacological treatment of gastric and duodenal ulcers (and of related syndromes) includes older and newer compounds, which have different mechanisms of action and exert different therapeutic effects. These compounds are widely prescribed in combination with other drugs being given for the treatment of concomitant diseases. This article reviews pharmacokinetic interactions with anti-ulcer drugs, paying particular attention to those which have clinically relevant adverse effects. Drugs mentioned in the literature as causing any pharmacokinetic interaction with anti-ulcer compounds are considered in this article.

Interactions between non-steroidal anti-inflammatory drugs and H2-receptor antagonists or prostaglandin analogues

Published pharmacokinetic studies investigating possible interaction between H2-receptor antagonists (n = 22) or prostaglandin analogues (n = 6) and nonsteroidal anti-inflammatory drugs (NSAIDs) have been reviewed. With two exceptions the studies were carried out in young, healthy male volunteers rather than in arthritis patients. In addition some of the studies were poorly designed and inadequately described. Cimetidine appeared to increase the area under the plasma concentration-time curve, and hence to decrease the apparent oral clearance, of several NSAIDs including piroxicam, indomethacin, flurbiprofen, sulindac, oxaprozin and aspirin, while ranitidine co-administration resulted in similar changes for oxyprozin alone. The data currently available for prostaglandin analogues are insufficient to draw firm conclusions. It therefore remains a possibility that clinically relevant pharmacokinetic interactions may occur in elderly arthritic patients, and this issue needs to be addressed.

Drug glucuronidation in humans

Glucuronidation is a major metabolic pathway for a large number of drugs in humans. Conjugation of drugs and other chemicals with glucuronic acid is catalyzed by the multigene UDP-glucuronosyltransferase family. It is believed that a number (unspecified at present) of glucuronosyltransferase isozymes, which probably differ in terms of substrate specificity and regulation, contribute to drug glucuronidation. Factors known to influence the pharmacokinetics of glucuronidated drugs in man, presumably via an effect on specific glucuronosyltransferases, include age (especially the neonatal period), cigarette smoking, diet, certain disease states, coadministered drugs, ethnicity, genetics and hormonal effects.