Although coinfected people are at risk for liver toxicity from ARVs, the benefit of HIV treatment outweighs the risk for liver toxicity.
Some side effects are more common in people with HCV coinfection, including lipodystrophy (fat accumulation or fat loss) and abnormal levels of fat and insulin in the blood. People with HCV monoinfection are far more likely to develop diabetes than the general population, and diabetes is more common among coinfected people than those with HIV alone. Use of HIV protease inhibitors and nucleoside analogs, especially stavudine (Zerit; d4T), has been linked with an increased risk for high blood sugar and diabetes.
However this risk should never be used as a reason to withhold HIV treatment.
Many HIV drugs are cleared from the body by the liver and have the potential to cause liver toxicity; HCV coinfection increases the risk by two to three times. This could be through the direct action of the drugs themselves -- largely a concern with nevirapine (a non-nucleoside reverse transcriptase inhibitor, or NNRTI), tipranavir, and higher doses of ritonavir (both protease inhibitors, or PIs) -- which can be managed by choosing other HIV drugs. The use of low-dose ritonavir to boost other PIs does not seem to increase this risk. Increased liver toxicity could also be the result of higher drug concentrations of NNRTIs and PIs, especially in people with more serious liver damage. Because a damaged liver is working less efficiently, the amount of drug in the blood could increase to dangerous levels and should (ideally) be checked using therapeutic drug monitoring (TDM) so that the dose can be modified if necessary.
DdI (didanosine, Videx) should not be used during HCV treatment, because of serious interactions with ribavirin that can cause lactic acidosis, pancreatitis, and the risk of liver failure in people with advanced cirrhosis. AZT is not recommended because of the increased risk of anemia.
When possible, d4T (stavudine) should be avoided during HCV treatment. Some studies have found that people who used d4T while treating their HCV were more likely to have significant weight loss and lipoatrophy (fat loss).
Other issues relating to HIV drugs are discussed below.
TDM is a blood test that checks whether you are getting adequate blood levels of a protease inhibitor, an NNRTI, and possibly T-20.
Doses for HIV drugs are worked out for an average person as a one-size-fits-all; however, individual differences in absorption can vary considerably in real life -- especially in people with reduced liver function related to HCV coinfection.
TDM is currently available only in research settings and certain clinics in the US, but it may be an important option if you're coinfected and having problems with your ARV regimen.