United Kingdom. The Committee on Safety of Medicines has identified several agents that interact with terfenadine: imidazole antifungals, macrolide antibiotics and grapefruit juice. Accumulation of terfenadine can cause cardiac arrhythmias when its hepatic metabolism is reduced by disease or by agents that interact with the relevant enzymes. Similar interactions have been found to occur with the following drugs and the Committee therefore recommends that they should not be used with terfenadine:

• mibefradil (PosicorR)
• serotonin reuptake inhibitors (fluvoxamine, nefazodone, sertraline)
• HIV protease inhibitors (indinavir, ritonavir, squinavir).
• cisapride.

[See also Pharmaceuticals Newsletter Nos. 9&10, September&October and Nos. 3&4, March&April 1997]

Reference: Current Problems in Pharmacovigilance Vol. 23, December 1997.