Use of single doses and rapid sampling to detect interactions with cimetidine.

In this study the well-established interaction between cimetidine and theophylline has been demonstrated using only a single dose of cimetidine. Eleven healthy subjects were given a 30 min infusion of theophylline on two separate occasions and plasma levels were monitored at frequent intervals. During one of the studies, a single 400 mg oral dose of cimetidine was given after collection of the 3 h sample. After normalisation of the control and test curves, a deflection was apparent in the test theophylline elimination curve in 9 out of 11 subjects. This method may provide a rapid screening method to detect such interactions.