Zomepirac is an orally effective NSAID that has antipyretic actions. It was developed by McNeil Pharmaceutical and approved by the FDA in 1980 and sold as the sodium salt, zomepirac sodium, under the brand name Zomax. Due to its clinical effectiveness, it was preferred by doctors in many situations and obtained a large share of the analgesics market; however, it was subsequently withdrawn in March 1983 due to its tendency to cause serious anaphylaxis in an unpredictable subset of the patient population.[1][2]


Zomepirac was indicated for the management of mild to severe pain.[3] Multiple clinical trials demonstrated zomepirac to be more effective than aspirin or codeine alone and to be as effective as analgesic combinations containing codeine or other opioids.[4][5][6][7][8][9][10] Zomepirac provided analgesia comparable with usual intramuscular doses of morphine in postoperative pain and that with long-term use, neither tolerance to its analgesic effect nor psychological or physical dependence had been demonstrated.[3][11]

Chemical structure

Zomepirac is the sodium salt of 5-(4-chlorobenzoyl)-1,4 dimethyl-1H-pyrrole-2-acetate dihydrate. It is a pyrrole-acetic acid which is structurally related to tolmetin.

Mechanism of action

It is a prostaglandin synthetase inhibitor.[12]


Zomepirac does not cause anaphylaxis directly, but it is metabolised by UGT to a reactive glucuronide, which binds irreversibly to plasma albumin.[13]