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Drug Interactions between AccessPak for HIV PEP Expanded with Viracept and Oromone

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

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Interactions between your drugs

Moderate

estradiol nelfinavir

Applies to: Oromone (estradiol) and AccessPak for HIV PEP Expanded with Viracept (emtricitabine / nelfinavir / tenofovir)

MONITOR: Coadministration of conjugated estrogens with ritonavir or nelfinavir may lead to decreased plasma concentrations of conjugated estrogens. The proposed mechanism may involve induction of the CYP450 3A4-mediated metabolism of conjugated estrogens by ritonavir and nelfinavir. Increased metabolism of estrogens may lead to decreased efficacy of the hormone replacement therapy. Ritonavir is a known CYP450 3A4 substrate and inhibitor; however, it has also been shown to reduce plasma concentrations of contraceptive hormones via a possible mechanism involving induction of glucuronosyltransferase and/or CYP450 hydroxylation. In addition, along with being a strong CYP450 3A4 inhibitor, nelfinavir has also been shown to possess CYP450 3A4-inducing properties.

MANAGEMENT: Dosage adjustments as well as increased clinical and laboratory monitoring should be considered whenever ritonavir or nelfinavir is added to or withdrawn from therapy with conjugated estrogens.

References

  1. "Product Information. Norvir (ritonavir)." Abbott Pharmaceutical PROD (2001):
  2. Ouellet D, Qian J, Locke CS, Eason CJ, Cavanaugh JH "Effect of ritonavir on the pharmacokinetics of ethinyl oestradiol in healthy female volunteers." Br J Clin Pharmacol 46 (1998): 111-6
  3. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0
  4. Dixit V, Hariparsad N, Li F, Desai P, Thummel KE, Unadkat JD "Cytochrome P450 enzymes and transporters induced by anti-human immunodeficiency virus protease inhibitors in human hepatocytes: implications for predicting clinical drug interactions." Drug Metab Dispos 35 (2007): 1853-9
  5. Cerner Multum, Inc. "Australian Product Information." O 0
  6. Faculty of Sexual & Reproductive Healthcare "FSRH Clinical Guidance: Drug Interactions with Hormonal Contraception. file:///C:/Users/df033684/Downloads/ceuguidancedruginteractionshormonal.pdf" (2016):
View all 6 references

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Drug and food interactions

Minor

estradiol food

Applies to: Oromone (estradiol)

Coadministration with grapefruit juice may increase the bioavailability of oral estrogens. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall induced by certain compounds present in grapefruits. In a small, randomized, crossover study, the administration of ethinyl estradiol with grapefruit juice (compared to herbal tea) increased peak plasma drug concentration (Cmax) by 37% and area under the concentration-time curve (AUC) by 28%. Based on these findings, grapefruit juice is unlikely to affect the overall safety profile of ethinyl estradiol. However, as with other drug interactions involving grapefruit juice, the pharmacokinetic alterations are subject to a high degree of interpatient variability. Also, the effect on other estrogens has not been studied.

References

  1. Weber A, Jager R, Borner A, et al. "Can grapefruit juice influence ethinyl estradiol bioavailability?" Contraception 53 (1996): 41-7
  2. Schubert W, Eriksson U, Edgar B, Cullberg G, Hedner T "Flavonoids in grapefruit juice inhibit the in vitro hepatic metabolism of 17B-estradiol." Eur J Drug Metab Pharmacokinet 20 (1995): 219-24

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Minor

tenofovir food

Applies to: AccessPak for HIV PEP Expanded with Viracept (emtricitabine / nelfinavir / tenofovir)

Food enhances the oral absorption and bioavailability of tenofovir, the active entity of tenofovir disoproxil fumarate. According to the product labeling, administration of the drug following a high-fat meal increased the mean peak plasma concentration (Cmax) and area under the concentration-time curve (AUC) of tenofovir by approximately 14% and 40%, respectively, compared to administration in the fasting state. However, administration with a light meal did not significantly affect the pharmacokinetics of tenofovir compared to administration in the fasting state. Food delays the time to reach tenofovir Cmax by approximately 1 hour. Tenofovir disoproxil fumarate may be administered without regard to meals.

References

  1. "Product Information. Viread (tenofovir)." Gilead Sciences (2001):

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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.

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

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