The Food and Drug Administration (FDA) has approved Stribild, a new combination of four drugs for the treatment of HIV. Stribild contains two new drugs, elvitegravir and cobicistat, as well as two previously approved anti-HIV drugs, emtricitabine (Emtriva) and tenofovir (Viread). The drug is approved for use in treatment-naïve patients infected with HIV-1 and is effective in reducing viral load and increasing CD4+-cell counts. The four drugs are combined in a single tablet taken once a day. Elvitegravir is an HIV integrase strand transfer inhibitor that prevents HIV from integrating itself into the genetic material of the host's cells. Cobicistat is considered a pharmacoenhancing or boosting agent. In the cytochrome P-450 (CYP) isoenzyme system, the enzyme CYP3A metabolizes certain drugs. Cobicistat blocks CYP3A-mediated metabolism and allows the anti-HIV drugs to remain in the systemic circulation longer.
Tenofovir and emtricitabine are nucleotide analog HIV-1 reverse transcriptase inhibitors that prevent viral RNA from creating viral DNA. Tenofovir and emtricitabine, like other drugs in the same class, have the potential to induce lactic acidosis and severe hepatomegaly with steatosis, which can be fatal. All preparations of tenofovir and emtricitabine, including Stribild, carry a boxed warning that lists these possible serious adverse effects. Stribild's label also includes a boxed warning that the drug hasn't been approved for the treatment of hepatitis B virus as a coinfection with HIV infection. Severe acute exacerbations of hepatitis B may occur if Stribild is discontinued. Other precautions include the possibility that the drug can cause a new onset or worsening of renal impairment, decreases in bone mineral density and osteomalacia, immune reconstitution syndrome, and fat redistribution and accumulation. The most common adverse effects—nausea, diarrhea, abnormal dreams, headache, and fatigue—aren't serious.
The FDA recommends that creatinine clearance, urine glucose, and urine protein values be obtained and documented in all patients prior to the start of treatment with Stribild. Serum phosphorus levels should also be measured in those at risk for renal impairment. Stribild should be discontinued if the patient's creatinine clearance falls below 50 mL per minute.
Nurses should conduct a thorough drug history before a patient begins treatment with Stribild, including assessment for use of over-the-counter or herbal supplements such as St. John's wort. Because of Stribild's effect on CYP3A, it shouldn't be coadministered with other drugs that rely on CYP3A for metabolism if elevations in the circulating plasma level of that drug are associated with serious or life-threatening events. The drug should also not be coadministered with drugs that increase the amount of CYP3A because that's likely to cause a loss of therapeutic effectiveness. Other nephrotoxic drugs should be avoided. Because antacids can decrease absorption, nurses should instruct patients to separate the administration of Stribild and antacids by at least two hours. Because a single, combination pill decreases the pill burden in patients undergoing HIV treatment, it should be easier for patients to adhere to Stribild therapy than to other treatment regimens. It is a complete regimen for HIV-1 treatment, and no other antiretroviral drugs should be coadministered.
Complete FDA prescribing information can be found at http://1.usa.gov/S7cbTX.