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Drug Interactions between efavirenz and tretinoin

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

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Interactions between your drugs

Moderate

tretinoin efavirenz

Applies to: tretinoin and efavirenz

MONITOR: Coadministration with efavirenz may decrease the plasma concentrations of retinoids that are substrates of the CYP450 3A4 isoenzyme such as alitretinoin, bexarotene, isotretinoin, and tretinoin. The mechanism is accelerated clearance due to induction of CYP450 3A4 activity by efavirenz.

MONITOR: Coadministration of efavirenz with other agents known to induce hepatotoxicity, including retinoids, may potentiate the risk of liver injury. Efavirenz has been associated with hepatotoxicity during postmarketing use. Among reported cases of hepatic failure, a few occurred in patients with no preexisting hepatic disease or other identifiable risk factors. Retinoids have been associated with hepatotoxicity ranging from transient and reversible increases in liver transaminases to clinical jaundice, hepatitis, and cirrhosis.

MANAGEMENT: Caution is advised if efavirenz must be used concomitantly with retinoids that undergo metabolism by CYP450 3A4. Pharmacologic response to the retinoid should be monitored more closely whenever efavirenz is added to or withdrawn from therapy, and the retinoid dosage adjusted as necessary. The risk of hepatic injury should also be considered during treatment with this combination. Patients should be advised to seek medical attention if they experience potential signs and symptoms of hepatotoxicity such as fever, rash, itching, anorexia, nausea, vomiting, fatigue, right upper quadrant pain, dark urine, light-coloured stools, and jaundice. Monitoring of liver function tests should occur before and during treatment, especially in patients with underlying hepatic disease (including hepatitis B or C coinfection) or marked transaminase elevations. The benefit of continued therapy with efavirenz and/or the retinoid should be considered against the unknown risks of significant liver toxicity in patients who develop persistent elevations of serum transaminases greater than five times the upper limit of normal.

References

  1. (2001) "Product Information. Accutane (isotretinoin)." Roche Laboratories
  2. (2001) "Product Information. Sustiva (efavirenz)." DuPont Pharmaceuticals
  3. (2001) "Product Information. Vesanoid (tretinoin)." Roche Laboratories
  4. (2001) "Product Information. Targretin (bexarotene)." Ligand Pharmaceuticals
  5. Cerner Multum, Inc. "UK Summary of Product Characteristics."
  6. Canadian Pharmacists Association (2006) e-CPS. http://www.pharmacists.ca/function/Subscriptions/ecps.cfm?link=eCPS_quikLink
View all 6 references

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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.

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

  1. (2001) "Product Information. Sustiva (efavirenz)." DuPont Pharmaceuticals

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Therapeutic duplication warnings

No warnings were found for your selected drugs.

Therapeutic duplication warnings are only returned when drugs within the same group exceed the recommended therapeutic duplication maximum.

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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

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