Effective and nontoxic new drugs for eradicating hepatitis C virus (HCV) have inspired a well-deserved wave of enthusiasm among clinicians. However, an intriguing pair of case reports suggests these drugs should be used with caution in HCV-positive patients who also are infected with hepatitis B virus (HBV). These two patients, HIV-negative men in their mid-50s, had chronic HBV and HCV genotype 1a infections; HCV treatment with peginterferon plus ribavirin had failed.

One patient had barely detectable HBV DNA (2300 IU/mL) at the beginning HCV treatment with sofosbuvir (Sovaldi) and simeprevir (Olysio). By week 4 after the start of treatment, HCV viral load was undetectable. At week 7, jaundice, abdominal pain, and other evidence of severe viral hepatitis developed; HCV RNA remained undetectable, but HBV DNA was 22 million IU/mL. HCV treatment was stopped, and HBV treatment with combination tenofovir and emtricitabine was begun. At week 28, the patient was well, and neither virus was detectable in his blood.

In the other patient, HBV viral load was monitored from the outset of treatment with sofosbuvir and simeprevir. HBV DNA was undetectable prior to treatment but rose to 11,255 IU/mL by week 4. Although the patient remained asymptomatic, tenofovir was added to the treatment regimen, and both viruses were undetectable at week 12.