Mefenamic acid adverse effects

Meclofenamate and mefenamic acid (Table 36-1) inhibit both COX and phospholipase A2. Meclofenamate appears to have adverse effects similar to those of other NSAIDs, though diarrhea and abdominal pain may be more common it has no advantages over other NSAIDs. This drug enhances the effect of oral anticoagulants. Meclofenamate is contraindicated in pregnancy its efficacy and safety have not been established for young children. 

Fenamic acid. The principal adverse effects of mefenamic acid are diarrhoea, upper abdominal discomfort, peptic ulcer and haemolytic anaemia. Elderly patients who take mefenamic acid may develop nonoliguric renal failure especially if they become dehydrated, e.g. by diarrhoea the drug should be avoided or used with close supervision in the elderly. 

Flufenamic acid and meclofenamic acid are anthranilic acid derivatives similar to mefenamic acid. The withdrawal rate because of adverse effects is 7-31% and is higher in longterm studies. Flufenamic acid and meclofenamic acid are not widely prescribed and so there is little evidence to show whether they have any advantages over other NSAIDs. Both have a high incidence of gastrointestinal adverse effects (30-60% of patients at recommended doses). Diarrhea affects 11 6% of patients (SEDA-4, 68) (SEDA-6, 99) (SEDA-7, 116) (SEDA-14, 95). Thrombocytopenia with positive rechallenge has been described (1). Rashes occur in under 10% of patients. Meclofenamic acid exacerbates psoriasis in psoriatic arthropathy (2). 

The NSAID mefenamic acid is an anthranilic acid derivative. It has been argned for more than a decade that, since there is a wide range of effective and less toxic drugs, there is no reason for continning to prescribe mefenamic acid and related drngs (SEDA-5, 93). All the same, some of the fignres have been dispnted, and, strictly speaking, a comparative controlled stndy to estimate the incidence of the adverse effects of mefenamic acid is still needed. The main reasons for concern are particular effects that are unexpected of an NSAID, such as hemolytic anemia, and which may therefore take the user by surprise. 

Gastrotoxicity due to mefenamic acid is marked. Other than the common adverse effects (nausea, anorexia, vomiting, pain, diarrhea), acute peptic ulcer, intestinal hemorrhage, hematemesis, abdominal distension, and profuse steatorrhea (SEDA-2, 97) have been reported. Mefenamic acid, unhke other NSAIDs, can provoke enteritis and cohtis in patients with no known predisposing factors (8). It accelerates bowel transit in healthy volunteers (SEDA-16,112). 

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