The Cao et al89 RCT did not show a significant increase in hepatotoxicity in the treatment compared to the control group. However, in patients with HIV, there is a well-documented known risk of hepatotoxicity, with liver injury severity ranging from mild enzyme elevations to acute liver failure.91 Moderate-to-severe elevations in serum aminotransferases, defined as more than 5 times the ULN, are found in 3%–10%.91 Rates may be higher in patients with concurrent HIV and hepatitis C virus co-infection. In some cases, mild asymptomatic elevations are self-limited and can resolve with continuation of the medication, but re-challenging the medication can also lead to recurrence and, therefore, should be avoided when possible. Acute liver failure, although reported, is rare. Ritonavir has potent effects on cytochrome P450 and therefore affects drug levels of a large number of medications typically given in GI practices.