Skip to main content

Drug Interactions between Estinyl and nelfinavir

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

Edit list (add/remove drugs)

Interactions between your drugs

Moderate

ethinyl estradiol nelfinavir

Applies to: Estinyl (ethinyl estradiol) and nelfinavir

ADDITIONAL CONTRACEPTION RECOMMENDED: Nelfinavir may decrease the plasma concentrations of contraceptive hormones during chronic coadministration. The proposed mechanism is nelfinavir induction of the hepatic metabolism of sex hormones. In 12 study subjects, nelfinavir (750 mg every 8 hours for 7 days) decreased the mean peak plasma concentration (Cmax), area under the concentration-time curve (AUC) and trough plasma concentration (Cmin) of ethinyl estradiol (administered as ethinyl estradiol-norethindrone 0.035 mg-0.4 mg once a day for 15 days) by 28%, 47% and 62%, respectively, compared to administration of the oral contraceptive alone. The mean AUC and Cmin of norethindrone decreased by 18% and 46%, respectively.

MANAGEMENT: Women using hormonal contraceptives should be advised of the risk of breakthrough bleeding and unintended pregnancy during concomitant therapy with nelfinavir. Alternative or additional methods of birth control should be used during and for at least 4 weeks after nelfinavir therapy.
-If a combination oral contraceptive pill is used, a regimen containing at least 50 mcg of ethinyl estradiol per day or equivalent should be selected. Although breakthrough bleeding is not necessarily indicative of low ethinyl estradiol serum levels or increased risk of ovulation, some clinicians suggest that women who experience breakthrough bleeding during enzyme-inducing therapy may be prescribed an increased dose of ethinyl estradiol above 50 mcg daily by combining more than one formulation of contraceptive pill if necessary.
-For emergency contraception in patients who have used an hepatic enzyme inducer in the past 4 weeks, a non-hormonal emergency contraceptive (e.g., copper intrauterine device) is considered preferable. If this is not possible, some authorities recommend that the usual dose of levonorgestrel (1.5 mg) should be doubled to 3 mg and taken as a single dose as soon as possible (within 72 hours of unprotected sexual intercourse). However, there are no data on efficacy, compliance, or side effects of this regimen.
-No precautions or recommendations are available for women using hormone-releasing intrauterine systems, but a significant interaction with these systems is thought to be unlikely due to their local action. -Injectable progestin-only contraceptives are also thought to be unaffected by enzyme-inducing drugs.

References

  1. "Product Information. Viracept (nelfinavir)." Agouron Pharma Inc PROD (2001):
  2. "FFPRHC Guidance (April 2005). Drug interactions with hormonal contraception." J Fam Plann Reprod Health Care 31 (2005): 139-51
  3. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0
  4. Faculty of Sexual & Reproductive Healthcare "FSRH Clinical Guidance: Drug Interactions with Hormonal Contraception. file:///C:/Users/df033684/Downloads/ceuguidancedruginteractionshormonal.pdf" (2016):
View all 4 references

Switch to consumer interaction data

Drug and food interactions

Minor

ethinyl estradiol food

Applies to: Estinyl (ethinyl 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

Switch to consumer interaction data

Minor

ethinyl estradiol food

Applies to: Estinyl (ethinyl estradiol)

The central nervous system effects and blood levels of ethanol may be increased in patients taking oral contraceptives, although data are lacking and reports are contradictory. The mechanism may be due to enzyme inhibition. Consider counseling women about this interaction which is unpredictable.

References

  1. Hobbes J, Boutagy J, Shenfield GM "Interactions between ethanol and oral contraceptive steroids." Clin Pharmacol Ther 38 (1985): 371-80

Switch to consumer interaction data

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

Report options

Loading...
QR code containing a link to this page

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.

Medical Disclaimer