Table 1.

Primary resistance mutations, frequency of resistance at one year and preferred management strategies to resistance with the approved nucleoside analogues.

Antiviral Agent	Primary antiviral resistant mutation	Frequency of resistance at 1 year		Preferred Management
		HBeAg (+)	HBeAg(−)
Lamivudine	rtM204V/I rtA181V/T	15–30%31, 32	11–27%81, 82	Add adefovir Add or switch to tenefovir
Telbivudine	rtM204I	5%12	2%12	Add adefovir Add or switch to tenefovir
Adefovir	rtA181V/T rtN236T	0%83	0%84	Add lamivudine or telbivudine Switch to tenofovir Switch to entecavir
Tenofovir	None	0%45	0%45
Entecavir	rtL180M & rtM204V plus rtI169T & rtM250V or rtT184G & rtS202I	0%52	0%34	? Add adefovir Add or switch to tenofovir