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Drug Interactions between Rescriptor and Systen

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

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Interactions between your drugs

Minor

estradiol delavirdine

Applies to: Systen (estradiol) and Rescriptor (delavirdine)

Serum concentrations and effects of medications that are metabolized by the 3A4 enzymatic pathways may theoretically be elevated in patients receiving delavirdine. The mechanism is inhibition of these enzymes by delavirdine. The clinical significance is unknown. Monitoring for clinical and laboratory evidence of safety and tolerance is recommended. Dosage adjustments or alternatives may be needed if an interaction is suspected.

References

  1. Cheng CL, Smith DE, Carver PL, Cox SR, Watkins PB, Blake DS, Kauffman CA, Meyer KM, Amidon GL, Stetson PL "Steady-state pharmacokinetics of delavirdine in HIV-positive patients: Effect on erythromycin breath test." Clin Pharmacol Ther 61 (1997): 531-43
  2. "Product Information. Rescriptor (delavirdine)." Pharmacia and Upjohn PROD (2001):
  3. Barry M, Mulcahy F, Merry C, Gibbons S, Back D "Pharmacokinetics and potential interactions amongst antiretroviral agents used to treat patients with HIV infection." Clin Pharmacokinet 36 (1999): 289-304
  4. Voorman RL, Maio SM, Payne NA, Zhao Z, Koeplinger KA, Wang X "Microsomal metabolism of delavirdine: evidence for mechanism-based inactivation of human cytochrome P450 3A." J Pharmacol Exp Ther 287 (1998): 381-8
  5. vonMoltke LL, Greenblatt DJ, Granda BW, Giancarlo GM, Duan SX, Daily JP, Harmatz JS, Shader RI "Inhibition of human cytochrome P450 isoforms by nonnucleoside reverse transcriptase inhibitors." J Clin Pharmacol 41 (2001): 85-91
  6. Fichtenbaum CJ, Gerber JG "Interactions between antiretroviral drugs and drugs used for the therapy of the metabolic complications encountered during HIV infection." Clin Pharmacokinet 41 (2002): 1195-211
View all 6 references

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Drug and food interactions

Minor

estradiol food

Applies to: Systen (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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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

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

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