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HIV Meds Quarterly
Interactions
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Summer 2011 issue
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Drug Interactions
Interactions
Buprenorphine/Naloxone with Raltegravir
Pitavastatin with Lopinavir/Ritonavir
Sustained Effect of Efavirenz on Rilpivirine Serum Concentrations
Hepatitis C NS3 Protease Inhibitors and Antiretroviral Drugs
Research Briefs
Preexposure Prophylaxis with Oral Tenofovir or Tenofovir/Emtricitabine
Dolutegravir in Treatment-Naive Patients
Lersivirine: A New NNRTI
Fast Takes
Rilpivirine approved

In May, the U.S. Food and Drug Administration granted approval to the NNRTI rilpivirine (Edurant) for use in treatment-naive patients with HIV-1 infection.

The recommended dosage is 25 mg once daily. It requires gastric acid for absorption, and therefore should be taken with a meal.

Important points emerged from registrational studies.

In Phase III studies, rilpivirine was compared with efavirenz, in combination with 2 NRTIs (predominantly tenofovir + emtricitabine). The overall rates of treatment failure were not significantly different in the two groups, but several important distinctions emerged:

Subjects who received rilpivirine had higher rates of virologic failure but lower rates of treatment discontinuation owing to adverse effects.
The higher rates of virologic failure in rilpivirine recipients occurred predominantly in those with pretreatment HIV RNA of >100,000 copies/mL.
Virologic failure on rilpivirine-containing regimens was commonly associated with resistance mutations to both NNRTI and NRTI agents, and with cross-resistance to other NNRTIs.

Little information is available on drug-drug interactions involving rilpivirine, but a number of important interactions have been recognized. Of the ARVs, efavirenz may cause a significant and prolonged lowering of rilpivirine concentrations even after it is discontinued, and it is not known whether it is safe to switch directly from efavirenz to rilpivirine (see Sustained Effect of Efavirenz on Rilpivirine Serum Concentrations). Important recognized interactions with other drugs include those with rifamycins (these drugs should be avoided) and acid-blocking medications (proton pump inhibitors should be avoided; other types require time-specific administration).

The package label is available on the FDA website.

1-pill, once-daily combination regimen: rilpivirine/tenofovir/emtricitabine
Following its approval of the NNRTI rilpivirine, the FDA has approved a coformulation of rilpivirine with tenofovir/emtricitabine. The new tablet contains standard dosages of the 3 constituent ARVs (25 mg/300 mg/200 mg, respectively) and is marketed under the brand name Complera. It is to be taken once daily with a meal, and thus is a 1-pill, once-daily complete regimen for initial therapy of adults with HIV-1 infection. Treating clinicians should, of course, consider the potential benefits and risks of the overall combination and of the individual components before prescribing.

The package label is available on the FDA website.

Etravirine 200 mg tablet approved

A new 200 mg tablet formulation of etravirine (Intelence) has been approved by the FDA and is available in pharmacies. This reduces the pill burden for patients taking etravirine. The recommended adult dosage is 200 mg BID.

HCV drug approvals

Two new drugs for treatment of hepatitis C have received approval from the FDA. Boceprevir (Victrelis) and telaprevir (Incivek) are the first available agents in the new class of HCV serine protease inhibitors. Each of them is to be used in combination with pegylated interferon and ribavirin for treatment of genotype 1 HCV. They improve the rates of virologic response, particularly in patients with HCV genotype 1 infection (which is more difficult to treat). Few data from patients with HIV/HCV coinfection have been reported; studies are ongoing. Few drug interaction studies have been conducted, but it is clear that each drug may have significant interactions with certain ARVs, particularly PIs and NNRTIs; see Hepatitis C NS3 Protease Inhibitors and Antiretroviral Drugs: interactions.

Reference Table
Updates to the Database of ARV Drug Interactions