There appears to be no pharmacokinetic interaction between entecavir and adefovir,lamivudine or tenofovir. However,interactions with other renally excreted drugs cannot be excluded. Nointeractions mediated by cytochrome P450 isoenzymes are expected with entecavir.
Clinical evidence,mechanism, importance and management
Since entecavir is predominantly eliminated by kidney, concurrent use of drugs that reduce renal function or compete for active tubular secretion may increase serum concentrations of either entecavir or concurrent drug. However, manufacturers note that there was no pharmacokinetic interaction between entecavir and lamivudine, adefovir or tenofovir at steady state (See reference number 1,2). They say that, apart from these drugs, effects of concurrent use of entecavir with drugs that are excreted renally or affect renal function have not been evaluated, and they therefore recommend that patients should be monitored closely for adverse reactions when entecavir is given (See reference number 1).
The manufacturers say that entecavir is not a substrate,an inducer or an inhibitor of cytochrome P450 isoenzymes. Therefore drug interactions are unlikely to occur with entecavir by this mechanism (See reference number 1,2).
Baraclude (Entecavir). Bristol-Myers Squibb Pharmaceuticals Ltd. UK Summary of productcharacteristics,July 2007.
Baraclude (Entecavir). Bristol-Myers Squibb Company. US Prescribing information,March2007.