Indobufen interacts with the sulphonylurea, glipizide, but not with the beta-adrenergic receptor antagonists, propranolol and atenolol.

This study assessed the possible interactions of the cyclooxygenase inhibitor indobufen with one sulphonylurea, glipizide, and with two beta-adrenoceptor antagonists, one of which is extensively metabolised already in the first passage through the liver (propranolol) while the other essentially escapes biotransformation (atenolol). Indobufen was first given as a single 200 mg dose and then for a 5 day period in a dosage of 200 mg twice daily, to six healthy volunteers. Glipizide (5 mg), propranolol (80 mg) and atenolol (100 mg) were given as single doses before and during indobufen medication. The drug concentrations were measured by selective and sensitive h.p.l.c. methods. The findings suggest that the lipophilic acid indobufen can inhibit the metabolic inactivation of another lipophilic acid, glipizide, but does not interfere with the disposal of the two basic drugs, propranolol and atenolol. The increased glipizide concentrations following indobufen were associated with an enhanced blood glucose reduction. Hence, this interaction may be clinically relevant.