Effects of Drospirenone on Other Drugs
Metabolism of DRSP and potential effects of DRSP on hepatic cytochrome P450 (CYP) enzymes have been investigated in in vitro and in vivo studies (see Metabolism). In in vitro studies, DRSP did not affect turnover of model substrates of CYP1A2 and CYP2D6, but had an inhibitory influence on the turnover of model substrates of CYP1A1, CYP2C9, CYP2C19 and CYP3A4 with CYP2C19 being the most sensitive enzyme. The potential effect of DRSP on CYP2C19 activity was investigated in a clinical pharmacokinetic study using omeprazole as a marker substrate. In the study with 24 postmenopausal women [including 12 women with homozygous (wild type) CYP2C19 genotype and 12 women with heterozygous CYP2C19 genotype] the daily oral administration of 3mg DRSP for 14 days did not affect the systemic clearance of the CYP2C19 substrate omeprazole (40 mg) and the CYP2C19 product 5-hydroxy-omeprazole. Furthermore, no significant effect of DRSP on the systemic clearance of the CYP3A4 product omeprazole sulfone was found. These results demonstrated that DRSP did not inhibit CYP2C19 and CYP3A4 in vivo.
Two further clinical drug-drug interaction studies using simvastatin and midazolam as marker substrates for CYP3A4, were each performed in 24 healthy, postmenopausal women. The results of these studies demonstrated that pharmacokinetics of the CYP3A4 substrates were not influenced by steady-state DRSP concentrations achieved after administration of 3 mg DRSP/day.
Based on the available results of in vivo and in vitro studies, it can be concluded that, at clinical dose level, DRSP is unlikely to interact significantly with cytochrome P450 enzymes.
In vitro and in vivo studies have shown that estrogens are metabolized partially by cytochrome P450 3A4 (CYP3A4). Therefore, inducers or inhibitors of CYP3A4 may affect estrogen drug metabolism. Inducers of CYP3A4 such as St. John's Wort preparations (Hypericum perforatum), phenobarbital, carbamazepine, and rifampin may reduce plasma concentrations of estrogens, possibly resulting in a decrease in therapeutic effects and/or changes in the uterine bleeding profile. Inhibitors of CYP3A4 such as erythromycin, clarithromycin, ketoconazole, itraconazole, ritonavir and grapefruit juice may increase plasma concentrations of estrogens and may result in side effects.
In cases of
overdose, monitor serum concentrations of potassium and sodium since drospirenone has antimineralocorticoid properties.
Serious ill effects have not been reported following acute ingestion of large doses of progestin/estrogen-containing oral contraceptives by young children. Overdosage may cause nausea and withdrawal bleeding may occur in females.
Progestogens/estrogens should not be used in individuals with any of the following conditions:
1. Undiagnosed abnormal genital bleeding.
2. Known, suspected, or history of cancer of the breast.
3. Known or suspected estrogen-dependent neoplasia.
4. Active deep vein thrombosis, pulmonary embolism or history of these conditions.
5. Active or recent (e.g., within the past year) arterial thromboembolic disease (e.g., stroke, myocardial infarction).
6. Renal insufficiency.
7. Liver dysfunction or disease.
8. Adrenal insufficiency.
should not be used in patients with known hypersensitivity to its ingredients.
10. Known or suspected pregnancy. There is no indication for
in pregnancy. There appears to be little or no increased risk of birth defects in children born to women who have used estrogens and progestins from oral contraceptives inadvertently during early pregnancy. (See Precautions).