The absence of appreciable effects of recombinant INF‐α2a on CYP3A4 is consistent with the conclusion that interferon‐α can be coadministered with the drugs metabolized by CYP1A2 and CYP3A4 in patients with chronic hepatitis C without significant risks of drug interactions, although an evaluation of CYP2B6 was not provided.7 On the other hand, pegylated INF‐α2a PEGASYS inhibited P450 1A2 and increased theophylline total exposure by 25% in healthy subjects.8 This evidence concerns the gene CYP3A4 and chronic hepatitis C virus infection.