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Drug Interactions between efavirenz and nevirapine

This report displays the potential drug interactions for the following 2 drugs:

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Interactions between your drugs

Moderate

nevirapine efavirenz

Applies to: nevirapine and efavirenz

GENERALLY AVOID: Coadministration of nevirapine and efavirenz has resulted in increased toxicity without additional therapeutic benefit over either agent alone. The mechanism of interaction has not been established, although this combination has exhibited strong antagonistic anti-HIV-1 activity in cell culture. In the double nonnucleoside study 2 NN, 1216 treatment-naive patients with plasma HIV-1 RNA greater than 5000 copies/ml at baseline were randomized to nevirapine 400 mg once daily, nevirapine 200 mg twice daily, efavirenz 600 mg once daily, or nevirapine 400 mg and efavirenz 800 mg once daily, plus stavudine and lamivudine for 48 weeks. Simultaneous use of nevirapine 400 mg and efavirenz 800 mg once daily was associated with the highest frequency of clinical adverse events and a higher rate of treatment failure (53.1%) at or before 48 weeks compared to nevirapine 200 mg twice daily (43.7%) or efavirenz 600 mg once daily (37.8%). Pharmacokinetically, nevirapine has been shown to reduce the plasma concentrations of efavirenz, presumably due to induction of the CYP450 3A4-mediated metabolism of efavirenz. In 14 HIV-positive subjects treated with an antiretroviral regimen containing efavirenz 600 mg once a day, the addition of nevirapine (200 mg once daily for 2 weeks followed by 400 mg once daily for 2 weeks) resulted in median decreases in efavirenz steady-state peak plasma concentration (Cmax), systemic exposure (AUC) and trough plasma concentration (Cmin) of 17%, 22% and 36%, respectively, compared to baseline. The clinical significance of these changes is unknown. The combination was well tolerated overall, with no reports of rash or other serious adverse events. Efavirenz did not appear to significantly alter the pharmacokinetics of nevirapine based on a comparison to historical control data.

MANAGEMENT: The combination of nevirapine and efavirenz is not recommended due to the efavirenz pharmacokinetic changes and the increased risk of toxicity associated with their coadministration. Moreover, no improvement in efficacy is observed during coadministration over either agent used alone. There has also been no determination of appropriate dosages for the safe and effective use of this combination.

References (3)
  1. (2001) "Product Information. Viramune (nevirapine)." Boehringer-Ingelheim
  2. Back D, Gibbons S, Khoo S (2003) "Pharmacokinetic drug interactions with nevirapine." J Acquir Immune Defic Syndr, 34 Suppl 1, S8-14
  3. Veldkamp AI, Montaner JS, Youle M, et al. (2001) "The steady-state pharmacokinetics of efavirenz and nevirapine when used in combination in human immunodeficiency virus type 1-infected persons." J Infect Dis, 184, p. 37-42

Drug and food interactions

Moderate

efavirenz food

Applies to: efavirenz

ADJUST DOSING INTERVAL: Administration with food increases the plasma concentrations of efavirenz and may increase the frequency of adverse reactions. According to the product labeling, administration of efavirenz capsules (600 mg single dose) with a high-fat/high-caloric meal (894 kcal, 54 g fat, 54% calories from fat) or a reduced-fat/normal-caloric meal (440 kcal, 2 g fat, 4% calories from fat) was associated with mean increases of 39% and 51% in efavirenz peak plasma concentration (Cmax) and 22% and 17% in systemic exposure (AUC), respectively, compared to administration under fasted conditions. For efavirenz tablets, administration of a single 600 mg dose with a high-fat/high-caloric meal (approximately 1000 kcal, 500-600 kcal from fat) resulted in a 79% increase in mean Cmax and a 28% increase in mean AUC of efavirenz relative to administration under fasted conditions.

GENERALLY AVOID: Alcohol may potentiate the central nervous system (CNS) depressant effects of efavirenz. Concomitant use may result in additive CNS depression and impairment of judgment, thinking, and psychomotor skills. In more severe cases, hypotension, respiratory depression, profound sedation, coma, or even death may occur.

MANAGEMENT: Efavirenz should be taken on an empty stomach, preferably at bedtime. Dosing at bedtime may improve the tolerability of nervous system symptoms such as dizziness, insomnia, impaired concentration, somnolence, abnormal dreams and hallucinations, although they often resolve on their own after the first 2 to 4 weeks of therapy . Patients should be advised of the potential for additive central nervous system effects when efavirenz is used concomitantly with alcohol or psychoactive drugs, and to avoid driving or operating hazardous machinery until they know how the medication affects them.

References (4)
  1. (2001) "Product Information. Sustiva (efavirenz)." DuPont Pharmaceuticals
  2. (2023) "Product Information. Sustiva (efavirenz)." Bristol-Myers Squibb, SUPPL-59/47
  3. (2024) "Product Information. Stocrin (efavirenz)." Merck Sharp & Dohme (Australia) Pty Ltd
  4. (2024) "Product Information. Efavirenz (efavirenz)." Viatris UK Healthcare Ltd

Therapeutic duplication warnings

Therapeutic duplication is the use of more than one medicine from the same drug category or therapeutic class to treat the same condition. This can be intentional in cases where drugs with similar actions are used together for demonstrated therapeutic benefit. It can also be unintentional in cases where a patient has been treated by more than one doctor, or had prescriptions filled at more than one pharmacy, and can have potentially adverse consequences.

Duplication

Nnrtis

Therapeutic duplication

The recommended maximum number of medicines in the 'NNRTIs' category to be taken concurrently is usually one. Your list includes two medicines belonging to the 'NNRTIs' category:

  • efavirenz
  • nevirapine

Note: In certain circumstances, the benefits of taking this combination of drugs may outweigh any risks. Always consult your healthcare provider before making changes to your medications or dosage.

See also

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Drug Interaction Classification

These classifications are only a guideline. The relevance of a particular drug interaction to a specific individual is difficult to determine. Always consult your healthcare provider before starting or stopping any medication.
Major Highly clinically significant. Avoid combinations; the risk of the interaction outweighs the benefit.
Moderate Moderately clinically significant. Usually avoid combinations; use it only under special circumstances.
Minor Minimally clinically significant. Minimize risk; assess risk and consider an alternative drug, take steps to circumvent the interaction risk and/or institute a monitoring plan.
Unknown No interaction information available.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

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