Drug interaction studies and safety of famciclovir in healthy volunteers: A review

Famciclovir is the diacetyl 6-deoxy derivative of the potent antiherpes agent penciclovir. The conversion of famciclovir to penciclovir, which is cleared renally, involves oxidative metabolism. This review discusses the results of four similarly designed studies conducted in healthy volunteers which investigated the potential interaction of famciclovir with allopurinol (an inhibitor of xanthine oxidase), cimetidine (an inhibitor of cytochrome P₄₅₀) and two drugs with a narrow therapeutic index, namely theophylline and digoxin. There was no evidence of clinically significant pharmacokinetic interactions between famciclovir and any of the co-administered drugs. Single-dose famciclovir was well tolerated by healthy volunteers following its administration alone or in combination with allopurinol, cimetidine, theophylline or digoxin. Furthermore, the adverse-event profile did not differ from that seen amongst the total number of volunteers who have received famciclovir to date.