Investigation of the potential interaction between terfenadine and tedisamil in human liver microsomes.

1. The potential drug-drug interaction of terfenadine and tedisamil has been investigated. Terfenadine is a widely used antihistamine drug with the potential for QTC prolongation. Tedisamil is a potassium channel blocking agent known to produce bradycardia and prolong the effective refractory period in man. 2. Tedisamil and terfenadine were incubated with human liver microsomes for 30 min at 37 degrees C. No significant inhibition of terfenadine biotransformation was seen with 0.1 or 10 microM tedisamil as the formation of the terfenadine alcohol and acid metabolites were unaffected. 3. Based on the in vitro results it is suggested that tedisamil will not interact pharmacokinetically with terfenadine as it does not impair metabolism of terfenadine.