For years the standard of care in patients with chronic hepatitis C has been 48 weeks of treatment with peginterferon alfa and ribavirin, although fewer than 50% of patients using this therapy are cured of the condition. Two new direct-acting antiviral drugs have recently been approved to treat this chronic illness: telaprevir (Incivek) and boceprevir (Victrelis). Both drugs are protease inhibitors specific for the hepatitis C virus, and neither of the new drugs produces cross-reactivity or cross-resistance with any of the protease inhibitors used to treat HIV.

Telaprevir is added to standard therapy in patients with hepatitis C who've not previously received interferon-based therapy or who've had a poor response to previous treatment.

The Food and Drug Administration (FDA) reported in May that in the various clinical trials to determine the safety and efficacy of telaprevir, a sustained virologic response was achieved 20% to 45% more often in patients taking telaprevir than in patients receiving only standard therapy. This was true across all of the studies and patient groups. Treatment with telaprevir shortens the recommended duration of therapy from 48 weeks to 24 weeks.

Telaprevir must be taken concurrently with peginterferon alfa and ribavirin. In studies its most common adverse effects were rash; fatigue; pruritus (all occurring in approximately 50% of patients); anemia; gastrointestinal symptoms (nausea, diarrhea, vomiting, and altered taste); and anorectal symptoms such as hemorrhoids, discomfort, and pruritus. Nurses who work with patients prescribed telaprevir need to provide specific patient education related to the duration of therapy. Telaprevir is taken orally three times a day, with seven to nine hours between doses, and should be taken with food that contains 20 g of fat (to promote absorption of the drug). The food should be eaten no more than 30 minutes before each dose of telaprevir. Examples of foods that contain 20 g of fat are a bagel with cream cheese, nuts (1/2 C), peanut butter (3 T), ice cream (1 C), American or cheddar cheese (2 oz.), potato chips (2 oz.), and trail mix (1/2 C). If a missed dose is discovered within four hours of the time the drug is normally taken, the dose may be made up then.

In studies of boceprevir used in combination with peginterferon alfa and ribavarin, it too significantly increased the rates of sustained virologic response. Adverse effects are similar to those of telaprevir. A major difference between these two direct-acting antivirals, however, is how the drugs react with food. Although food does increase the bioavailability of boceprevir, the amount of fat in the food doesn't affect the drug's absorption, nor is the timing of the food as important: boceprevir may be taken just before, during, or immediately after a meal. Both men and women who are capable of reproducing should be instructed to use two forms of birth control while taking either drug and for six months after stopping it.

For more information on telaprevir and boceprevir, see the FDA's complete prescribing information: http://1.usa.gov/iZRoW7 and http://1.usa.gov/jUQ9ov.