Tenofovir Entecavir

All the nucleoside (and nucleotide) analogues that have entered the clinic for the treatment of HBV infections (i.e., nucleoside analogues lamivudine, entecavir, tel-bivudine nucleotide analogues adefovir and tenofovir) are fairly well tolerated without side effects that would preclude their long-term usage. The nucleoside analogues in (pre)clinical development for the treatment of HCV infections are not yet sufficiently advanced to assess their tolerability and/or safety. 

In addition to the NRTI lamivudine (3TC) and the NtRTI adefovir dipivoxU and tenofovir disoproxil fumarate (which has been recently licensed for the treatment of chronic hepatitis B), two other nucleoside analogues, that is, entecavir and L-dT (tel-bivudine) (Fig.4aa), have been licensed for the treatment of HBV infections. Two other compounds 3 -Val-L-dC (valtorcitabine) and L-FMAU (clevudine) (Fig. 4aa) are in clinical development for the treatment of HBV infections, and yet two other compounds, that is, racivir and elvucitabine (Fig. 3), yield potential for the treatment of both HBV and HIV infections. 

The therapeutic armementarium in this field is enlarging with promising results but at the expense of viral resistance and cost.The drugs used in HBV treatment are mainly interferons (mostly pegylated), and nucleos(t)ide analogs (Lamivudine, Adefovir and the more recent ones Telbivudine, Entecavir and Tenofovir). Different... 

There appears to be no pharmacokinetic interaction between entecavir and adefovir, iamivudine or tenofovir. However, interactions with other renaiiy excreted drugs cannot be excluded. No interactions mediated by cytochrome P450 isoenzymes are expected with entecavir. 

Since entecavir is predominantly eliminated by the kidney, the concurrent use of drugs that reduee renal funetion or eompete for aetive tubular secretion may increase serum concentrations of either enteeavir or the concurrent drug. However, the manufaeturers note that there was no pharmacokinetic interaction between enteeavir and iamivudine, adefovir or tenofovir at steady state.They say that, apart from these drugs, the effects of concurrent use of enteeavir with drugs that are excreted renally or affect renal funetion have not been evaluated, and they therefore recommend that patients should be monitored elosely for adverse reactions when enteeavir is given. ... 

Koklu S, Tuna Y, Gulsen MT, Demir M, Koksal AS, Kockar MC, et al. Long-term efiicacy and safety of lamivudine, entecavir, and tenofovir for treatment of hepatitis B virus-related cirrhosis. Clin Gastroenterol Hepatol 2013 ll(l) 88-94. 

Gish RG, Clark MD, Kane SD, Shaw RE, Mangahas MF, Baqai S. Similar risk of renal events among patients treated with tenofovir or entecavir for chronic hepatitis B. Clin Gastroenterol Hepatol 2012 10(8) 941-6. 

Pol S, Lampertico. First-line treatment of chronic hepatitis B with entecavir or tenofovir in real-life settings from clinical trials to clinical practice. J Viral Hepat 2012 19(6) 377-86. 

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