Estradiol Drug Interactions

by on June 28, 2012

Estradiol is a female sex hormone. It is also available in the form of medicine used for the treatment of menopausal symptoms, replacement therapy after gynecological surgeries and sometimes as a part of the in vitro programs. It is also part of some contraceptive pills.

Estradiol is metabolized by a group of liver enzymes called cytochrome P450. A subclass of this group known as CYP 3A4 is particularly responsible for the deactivation and metabolism of estradiol. A lot of drugs can inhibit or induce the activity of these enzymes changing, in this way, the serum concentrations and activity of estradiol. These drugs should be avoided while you are treated with estradiol. In case you need to take them or any other drugs, including OTC ones, herbs and dietary supplements, you should inform your doctor as dose adjustment of estardiol may be necessary.

Medicines that reduce the effect of estradiol

  • Some medicines used for the treatment of epilepsy such as phenytoin (Dilantin) and carbamazepine (Tegretol).
  • phenobarbital (Luminal)
  • some antibiotics used for the treatment of tuberculosis and other infections such as rifampicin(Rifadin, Rimactane),  Rifabutin
  • some non-nucleoside reverse transcriptase inhibitors used for the treatment of HIV infection  such as efavirenz(Sustiva, Stocrin) and nevirapine(Viramune).
  • St John's wort or medicines containing St John's wort extract.

These medicines induce the activity of CYP 3A4 leading to faster deactivation of estradiol.

Medicines that enhance the effect of estradiol

  • Some macrolide antibiotics such as erythromycin (Robimycin, EryPed, Erymax) and clarithromycin (Klacid).
  • Some azole antifungal medicines such as ketoconazole (Nizoral) and itraconazole (Orungal)
  • Some HIV medicines such as ritonavir(Norvir), nelfinavir(Viracept)
  • Grapefruit juice

These medicines can increase the plasma concentrations and lead to more frequent occurrence of  adverse effects.

Other interactions

  • Estradiol interferes with the activity of some blood thinners such as Warfarin and Sintrom which leads to higher risk of thrombosis.
  • When estradiol is administered orally, it should not be combined with salycilates or atropine-containing medicines.
  • It should not be combined with oral contraceptives.
  • Alcohol can increase the tumor-stimulating effects of estradiol. Avoid drinking alcohol during the treatment with estradiol. If you have any questions, do not hesitate to discuss them with your healthcare provider. Avoid smoking during the therapy.
  • The combination of estradiol and progesterone is usually beneficial as it decreases the risk of development of uterine cancer. Ask your doctor for more information as every case is different.

This list is not complete and other drugs can also interact with estradiol and its derivates. If you are prescribed medicines containing estradiol or some of its derivates, inform your healthcare provider about any prescription, over-the-counter medicines, herbs or dietary supplements that you are using.