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Drug Interactions between Estinyl and oxtriphylline

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

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Interactions between your drugs

Moderate

ethinyl estradiol oxtriphylline

Applies to: Estinyl (ethinyl estradiol) and oxtriphylline

MONITOR: The coadministration with contraceptive steroids may increase the plasma concentrations of theophylline and other methylxanthines. The proposed mechanism is inhibition of methylxanthine metabolism via hepatic microsomal enzymes, of which estrogens and progestins are also substrates. In one study, theophylline clearance was approximately 30% lower in oral contraceptive users than in nonusers. However, clinical data have been conflicting.

MANAGEMENT: Caution is advised during concomitant therapy with methylxanthines and hormonal contraceptives. Serum theophylline levels and pharmacologic response should be monitored and the dosage adjusted accordingly, particularly following initiation or discontinuation of hormonal contraceptives in patients who are stabilized on their theophylline regimen. Patients should be advised to notify their physician if they experience signs and symptoms of theophylline toxicity such as nausea, vomiting, diarrhea, headache, restlessness, insomnia, and irregular heartbeat.

References

  1. Tornatore KM, Kanarkowski R, McCarthy TL, et al. "Effect of chronic oral contraceptive steroids on theophylline disposition." Eur J Clin Pharmacol 23 (1982): 129-34
  2. Gardner MJ, Tornatore KM, Jusko WJ, Kanarkowski R "Effects of tobacco smoking and oral contraceptive use on theophylline disposition." Br J Clin Pharmacol 16 (1983): 271-80
  3. Roberts RK, Grice J, McGuffie, Heilbronn L "Oral contraceptive steroids impair the elimination of theophylline." J Lab Clin Med 101 (1983): 821-25

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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

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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

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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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