Tadalafil Theophylline

A double-blind, placebo-controlled, randomised, crossover study in 17 healthy subjects given enough oral theophylline (a non-selective phosphodiesterase inhibitor) to achieve steady-state levels of about 12 mg/L found that the concurrent use of tadalafil 10 mg daily for 7 days did not affect the pharmacokinetics of either drug. There was a small increase of 3.5 bpm in the heart rate, which was not considered to be clinically relevant in the healthy subjects, but the UK manufacturers advise that this should be considered when both drugs are used concurrently. ... 

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