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Drug Interactions between efavirenz and Prezista

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

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Interactions between your drugs

Moderate

efavirenz darunavir

Applies to: efavirenz and Prezista (darunavir)

MONITOR: Coadministration with efavirenz may decrease the plasma concentrations of darunavir, even in the presence of cobicistat or low-dose ritonavir as a pharmacokinetic booster. Additionally, the plasma concentration of cobicistat may be reduced. Reduced darunavir plasma levels may lead to diminished virologic response and possible resistance to darunavir. The mechanism is efavirenz induction of CYP450 3A4, the isoenzyme responsible for the metabolic clearance of darunavir and cobicistat. In 12 study subjects, administration of darunavir/ritonavir (300 mg/100 mg twice a day) with efavirenz (600 mg once a day) decreased the peak plasma concentration (Cmax), area under the concentration-time curve (AUC) and trough plasma concentration (Cmin) of darunavir by 15%, 13% and 31%, respectively, compared to administration without efavirenz. In contrast, efavirenz Cmax, AUC, and Cmin increased by 15%, 21%, and 17%, respectively, in the presence of darunavir/ritonavir. The clinical significance of these changes are unknown. Data are not available for darunavir-cobicistat.

MANAGEMENT: Caution is advised if darunavir-ritonavir is coadministered with efavirenz. Antiretroviral response should be monitored closely and darunavir-ritonavir dose adjusted if necessary. Some authorities recommend a dose adjustment of darunavir 600 mg-ritonavir 100 mg twice daily. Concomitant use of darunavir-cobicistat with efavirenz is not recommended.

References

  1. Cerner Multum, Inc. "UK Summary of Product Characteristics."
  2. (2006) "Product Information. Prezista (darunavir)." Ortho Biotech Inc
  3. Cerner Multum, Inc. "Australian Product Information."
  4. (2014) "Product Information. Prezcobix (cobicistat-darunavir)." Janssen Pharmaceuticals
View all 4 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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Moderate

darunavir food

Applies to: Prezista (darunavir)

ADJUST DOSING INTERVAL: Food enhances the absorption and oral bioavailability of darunavir administered in combination with low-dose ritonavir. The mechanism is unknown. When administered with food, the peak plasma concentration (Cmax) and area under the plasma concentration-time curve (AUC) of darunavir were approximately 30% higher than when administered in the fasting state. Darunavir exposure was similar for the range of meals studied. The total caloric content of the various meals evaluated ranged from 240 Kcal (12 grams fat) to 928 Kcal (56 grams fat).

MANAGEMENT: To ensure maximal oral absorption, darunavir coadministered with ritonavir should be taken with food. The type of food is not important.

References

  1. (2006) "Product Information. Prezista (darunavir)." Ortho Biotech Inc

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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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