<unk>  is metabolized predominantly by the hepatic CYP3A4 enzyme system. The presence of other drugs which induce this system can shorten<unk>  half-life and reduce serum levels, and hence efficacy, of the drug.
Tadalafil
Avanafil
Vardenafil
Udenafil
Finasteride
Ingenol mebutate
Protollin
Acebutolol