Dear Dr McGovern,

I have a question regarding the anti-viral drug telbivudine. I am taking Tyzeka to suppress HBV replication (without coinfection from HIV or HCV ), but I do not have liver cirrhosis. What is the consequence of a few missed doses? Will a couple of consecutive missed doses ruin the therapy?

I am asking this question because I heard HIV drugs are effective as long as the patient stick to the schedule nearly 100% of the times. Even a couple missed doses can lead to drug resistance.

Is this the same case with HBV anti-viral treatment? Will I suffer severe liver damage after a couple missed doses? Will drug resistance develop quickly as a result of that?

Thanks!

Thank you for your excellent question. Any time we have to take a chronic medication, sometimes pills are missed. In patients with diabetes or high blood pressure, this can result in a bad outcome, like a hyperglycemic coma or a stroke. However, when the patient starts to take the medication faithfully - it works as well as ever.

However, with medications against viral infections, like HIV, missed doses can lead to drug resistance. Your example of HIV is the best one, because patients must do their best not to miss doses. With HBV, resistance can also occur, but it does not seem to be anywhere near as costly as in HIV. HBV resistance does occur, but at much slower rates than with HIV.

I am not encouraging sloppy adherence however. HBV resistance has a lot of implications too - since there is cross-resistance from one drug to other drugs. Try to stick to your schedule as faithfully as possible.

You should also have viral load monitoring over time to be certain you are getting a good result.

Best of luck.