Efavirenz: Price, Dosage & Where to Buy

Efavirenz is an antiretroviral medicine belonging to the non-nucleoside reverse transcriptase inhibitor class, used with other antiretroviral medicines to treat human immunodeficiency virus type 1 (HIV-1) infection. It is used in adults and eligible children, rather than as a treatment on its own, and requires a prescription in the United Kingdom.

Efavirenz is indicated for the treatment of HIV-1 infection in adults and children at least 3 months old who weigh at least 3.5 kg. Its use is always in combination with other antiretroviral medicines.

The label does not support using efavirenz alone or adding it as the only new medicine to a treatment combination that is failing. Selection of the accompanying medicines needs to account for the possibility of viral resistance, including cross-resistance to other antiretroviral agents.

The label lists oral capsules containing 50 mg, 100 mg and 200 mg, and oral tablets, including film-coated tablets, containing 600 mg. The label lists the recommended adult dosage as 600 mg orally once daily, in combination with other antiretroviral medicines, on an empty stomach, preferably at bedtime. Food can increase efavirenz concentrations and the frequency of adverse reactions; bedtime administration may improve tolerability of nervous system symptoms.

The label lists weight-based paediatric dosing, with 600 mg once daily for children weighing 40 kg or more. A capsule sprinkle method is described for children who cannot swallow capsules. Tablets must not be broken or crushed.

The label lists an increase to 800 mg once daily with rifampin for patients weighing 50 kg or more. The label lists an efavirenz reduction to 300 mg once daily using capsules when coadministered with voriconazole, alongside adjustment of voriconazole. Liver function monitoring is recommended before and during treatment.

Efavirenz belongs to a class called non-nucleoside reverse transcriptase inhibitors. HIV uses an enzyme called reverse transcriptase to copy its genetic material during replication. Medicines in this class bind to that enzyme and interfere with its activity, helping to limit the virus's ability to multiply.

Efavirenz is combined with other antiretroviral medicines so that treatment acts against the virus through complementary mechanisms. Using it alone allows resistant virus to emerge rapidly.

The label advises that efavirenz should not be used in the first trimester because of a potential risk of neural tube defects. Reports exist, but a causal relationship has not been established, and prospective data are insufficient to assess this risk adequately. Pregnancy testing before treatment and effective contraception during treatment and for 12 weeks after stopping are recommended.

Barrier contraception should accompany other methods, as progesterone-containing hormonal methods may be less effective. The label recommends against breastfeeding because of the potential for HIV transmission.

A missed dose interrupts the regular schedule of antiretroviral treatment. General pharmacy advice is to resume a missed dose when remembered unless the next scheduled dose is nearly due; in that case, the missed dose is omitted.

A double dose should not be used to compensate. A pharmacist or HIV treatment team can clarify the appropriate approach, particularly after repeated missed doses.

The label specifies storage of efavirenz tablets at 20° to 25°C, with excursions permitted to 15° to 30°C. Keep medicines out of the sight and reach of children and follow the pack's storage directions to maintain quality.