indication

For the relief of mild to moderate pain, for the treatment of primary dysmenorrhea and for the treatment of idiopathic heavy menstrual blood loss. Also for relief of the signs and symptoms of acute and chronic rheumatoid arthritis and osteoarthritis.

pharmacology

Meclofenamic acid is a nonsteroidal agent which has demonstrated anti-inflammatory, analgesic, and antipyretic activity in laboratory animals.

mechanism of action

The mode of action, like that of other nonsteroidal anti-inflammatory agents, is not known. Therapeutic action does not result from pituitary-adrenal stimulation. In animal studies, meclofenamic acid was found to inhibit prostaglandin synthesis and to compete for binding at the prostaglandin receptor site. In vitro meclofenamic acid was found to be an inhibitor of human leukocyte 5-lipoxygenase activity. These properties may be responsible for the anti-inflammatory action of meclofenamic acid. There is no evidence that meclofenamic acid alters the course of the underlying disease.

toxicity

After a massive overdose, CNS stimulation may be manifested by irrational behavior, marked agitation and generalized seizures. Following this phase, renal toxicity (falling urine output, rising creatinine, abnormal urinary cellular elements) may be noted with possible oliguria or anuria and azotemia. A 24 year-old male was anuric for approximately one week after ingesting an overdose of 6 to 7 grams of meclofenamate sodium. Spontaneous diuresis and recovery subsequently occurred.

biotransformation

Hepatic. Meclofenamic acid is extensively metabolized to an active metabolite (Metabolite I; 3-hydroxymethyl metabolite of meclofenamic acid) and at least six other less well characterized minor metabolites. Only Metabolite I has been shown in vitro to inhibit cyclooxygenase activity with approximately one fifth the activity of meclofenamic acid.

absorption

Rapidly absorbed in man following single and multiple oral doses with peak plasma concentrations occurring in 0.5 to 2 hours. The concomitant administration of antacids (aluminum and magnesium hydroxides) does not interfere with absorption of meclofenamic acid. Unlike most NSAIDs, which when administered with food have a decrease in rate but not in extent of absorption, meclofenamic acid is decreased in both. It has been reported that following the administration of meclofenamic acid capsules one-half hour after a meal, the average extent of bioavailability decreased by 26%, the average peak concentration (C_max) decreased fourfold and the time to C_max was delayed by 3 hours.

half life

In a study in 10 healthy subjects following a single oral dose the apparent elimination half-life ranged from 0.8 to 5.3 hours. Metabolite I (3-hydroxymethyl metabolite of meclofenamic acid) has a mean half-life of approximately 15 hours.

route of elimination

Other metabolites, whose excretion rates are unknown, account for the remaining 35% to 62% of the dose excreted in the urine. The remainder of the administered dose (approximately 30%) is eliminated in the feces (apparently through biliary excretion). Trace amounts of meclofenamate sodium are excreted in human breast milk.

drug interactions

Colesevelam: Bile acid sequestrants may decrease the absorption of Nonsteroidal Anti-Inflammatory Agents. Monitor for decreased serum concentrations/therapeutic effects of nonsteroidal anti-inflammatory agents (NSAID) if coadministered with bile acid sequestrants. Separating the administration of doses by 2 or more hours may reduce (but not eliminate) the risk of interaction. The manufacturer of colesevelam recommends that drugs should be administered at least 1 hour before or 4 hours after colesevelam.

Cyclosporine: Monitor for nephrotoxicity

Ginkgo biloba: Additive anticoagulant/antiplatelet effects may increase bleed risk. Concomitant therapy should be avoided.

Methotrexate: The NSAID, meclofenamic acid, may decrease the renal excretion of methotrexate. Increased risk of methotrexate toxicity.

Telmisartan: Concomitant use of Telmisartan and Meclofenamic acid may increase the risk of acute renal failure and hyperkalemia. Monitor renal function at the beginning and during treatment.

Timolol: The NSAID, Meclofenamate, may antagonize the antihypertensive effect of Timolol.

Trandolapril: The NSAID, Meclofenamate, may reduce the antihypertensive effect of Trandolapril. Consider alternate therapy or monitor for changes in Trandolapril efficacy if Meclofenamate is initiated, discontinued or dose changed.

Treprostinil: The prostacyclin analogue, Treprostinil, may increase the risk of bleeding when combined with the NSAID, Meclofenamate. Monitor for increased bleeding during concomitant thearpy.

Warfarin: The antiplatelet effects of meclofenamic acid may increase the bleed risk associated with warfarin. Consider alternate therapy or monitor for signs and symptoms of bleeding during concomitant therapy.