flora. Applies only to oral forms of hormone. Low risk of contraceptive failure. Use Caution/Monitor.pentobarbitalMonitor Closely (1)pentobarbital will decrease the level or effect of mestranol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.Serious - Use Alternative (1)pentobarbital decreases levels of mestranol by increasing metabolism. Avoid or Use Alternate Drug. May result in contraceptive failure.phenindioneSerious - Use Alternative (1)mestranol decreases effects of phenindione by pharmacodynamic antagonism. Contraindicated. Risk of thromboembolic disorders.phenobarbitalMonitor Closely (2)phenobarbital will decrease the level or effect of mestranol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. phenobarbital will decrease the level or effect of mestranol by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.Serious - Use Alternative (1)phenobarbital decreases levels of mestranol by increasing metabolism. Avoid or Use Alternate Drug. May result in contraceptive failure.phenytoinMonitor Closely (3)phenytoin will decrease the level or effect of mestranol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. phenytoin will decrease the level or effect of mestranol by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. mestranol decreases effects of phenytoin by decreasing metabolism. Use Caution/Monitor.Serious - Use Alternative (1)phenytoin decreases levels of mestranol by increasing metabolism. Avoid or Use Alternate Drug. May result in contraceptive failure.phytoestrogensMinor (1)phytoestrogens decreases effects of mestranol by pharmacodynamic antagonism. Minor/Significance Unknown.pioglitazoneMinor (1)pioglitazone decreases levels of mestranol by unknown mechanism. Minor/Significance Unknown.pivmecillinamMonitor Closely (1)pivmecillinam will decrease the level or effect of mestranol by altering intestinal flora. Applies only to oral forms of hormone. Low risk of contraceptive failure. Use Caution/Monitor.pleurisy rootMinor (1)pleurisy root decreases effects of mestranol by unspecified interaction mechanism. Minor/Significance Unknown. Theoretical interaction.posaconazoleMonitor Closely (1)posaconazole will increase the level or effect of mestranol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.Minor (1)posaconazole decreases effects of mestranol by increasing metabolism. Minor/Significance Unknown. May also cause menstrual irregularities.prednisoneMonitor Closely (1)prednisone will decrease the level or effect of mestranol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.primidoneMonitor Closely (1)primidone will decrease the level or effect of mestranol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.Serious - Use Alternative (1)primidone decreases levels of mestranol by increasing metabolism. Avoid or Use Alternate Drug. Contraceptive failure may result.protamineSerious - Use Alternative (1)mestranol decreases effects of protamine by pharmacodynamic antagonism. Contraindicated. Risk of thromboembolic disorders.protriptylineMinor (1)mestranol, protriptyline. Mechanism: unspecified interaction mechanism. Minor/Significance Unknown. Estrogens and progestins may decr tricyclic antidepressant effects, while increasing TCA plasma concentration and adverse effects.pyridoxineMinor (1)mestranol decreases levels of pyridoxine by altering metabolism. Minor/Significance Unknown.pyridoxine (Antidote)Minor (1)mestranol decreases levels of pyridoxine (Antidote) by altering metabolism. Minor/Significance Unknown.quercetinMonitor Closely (1)quercetin will decrease the level or effect of mestranol by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.quinidineSerious - Use Alternative (1)quinidine will increase the level or effect of mestranol by P-glycoprotein (MDR1) efflux transporter. Avoid or Use Alternate Drug.quinupristin/dalfopristinMonitor Closely (2)quinupristin/dalfopristin will increase the level or effect of mestranol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. quinupristin/dalfopristin will decrease the level or effect of mestranol by altering intestinal flora. Applies only to oral forms of hormone. Low risk of contraceptive failure. Use Caution/Monitor.ranolazineMonitor Closely (1)ranolazine will increase the level or effect of mestranol by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.ribociclibMonitor Closely (1)ribociclib will increase the level or effect of mestranol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.rifabutinSerious - Use Alternative (2)rifabutin will decrease the level or effect of mestranol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. rifabutin decreases levels of mestranol by increasing metabolism. Avoid or Use Alternate Drug. May result in contraceptive failure.rifampinMonitor Closely (1)rifampin will decrease the level or effect of mestranol by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.Serious - Use Alternative (2)rifampin will decrease the level or effect of mestranol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. rifampin decreases levels of mestranol by increasing metabolism. Avoid or Use Alternate Drug. May result in contraceptive failure.rifapentineMonitor Closely (1)rifapentine will decrease the level or effect of mestranol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.Serious - Use Alternative (1)rifapentine decreases levels of mestranol by increasing metabolism. Avoid or Use Alternate Drug. May result in contraceptive failure.ritonavirMonitor Closely (3)ritonavir will increase the level or effect of mestranol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. ritonavir will increase the level or effect of mestranol by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. ritonavir decreases levels of mestranol by increasing metabolism. Use Caution/Monitor. May result in contraceptive failure; use additional or alternative method.romidepsinMonitor Closely (1)romidepsin decreases effects of mestranol by receptor binding competition. Use Caution/Monitor.ropiniroleMinor (1)mestranol increases levels of ropinirole by unspecified interaction mechanism. Minor/Significance Unknown.rose hipsMinor (1)mestranol decreases levels of rose hips by increasing elimination. Minor/Significance Unknown.rosuvastatinMinor (1)rosuvastatin increases levels of mestranol by unspecified interaction mechanism. Minor/Significance Unknown.roxithromycinMonitor Closely (1)roxithromycin will decrease the level or effect of mestranol by altering intestinal flora. Applies only to oral forms of hormone. Low risk of contraceptive failure. Modify Therapy/Monitor Closely.rufinamideMonitor Closely (1)rufinamide will decrease the level or effect of mestranol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.ruxolitinibMinor (1)mestranol will increase the level or effect of ruxolitinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.ruxolitinib topicalMinor (1)mestranol will increase the level or effect of ruxolitinib topical by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.saquinavirSerious - Use Alternative (1)saquinavir will increase the level or effect of mestranol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.secobarbitalMonitor Closely (1)secobarbital will decrease the level or effect of mestranol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.Serious - Use Alternative (1)secobarbital decreases levels of mestranol by increasing metabolism. Avoid or Use Alternate Drug. May result in contraceptive failure.selegiline transdermalMonitor Closely (1)mestranol increases levels of selegiline transdermal by Other (see comment). Use Caution/Monitor. Comment: Oral contraceptives inhibit the N demethylatin of selegiline.siltuximabMonitor Closely (1)siltuximab, mestranol. Other (see comment). Use Caution/Monitor. Comment: CYP450 activity in the liver is down regulated by infection and inflammation stimuli including cytokines (eg, IL-6); inhibition of IL-6 by siltuximab may restore CYP450 enzymatic activity; caution if coadministered with CYP substrates that have a narrow therapeutic index.simvastatinMonitor Closely (1)simvastatin will increase the level or effect of mestranol by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.sirolimusMonitor Closely (1)sirolimus will increase the level or effect of mestranol by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.sodium tetradecyl sulfateMinor (1)sodium tetradecyl sulfate increases toxicity of mestranol by pharmacodynamic synergism. Minor/Significance Unknown. Increased risk of thromboembolic disorder.St John's WortMonitor Closely (1)St John's Wort will decrease the level or effect of mestranol by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.Serious - Use Alternative (1)St John's Wort will decrease the level or effect of mestranol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.stiripentolMonitor Closely (1)stiripentol, mestranol. affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Stiripentol is a CYP3A4 inhibitor and inducer. Monitor CYP3A4 substrates coadministered with stiripentol for increased or decreased effects. CYP3A4 substrates may require dosage adjustment.streptomycinMonitor Closely (1)streptomycin will decrease the level or effect of mestranol by altering intestinal flora. Applies only to oral forms of hormone. Low risk of contraceptive failure. Use Caution/Monitor.sugammadexMonitor Closely (1)sugammadex decreases levels of mestranol by unspecified interaction mechanism. Use Caution/Monitor. Risk of contraceptive failure.sulfadiazineMonitor Closely (1)sulfadiazine will decrease the level or effect of mestranol by altering intestinal flora. Applies only to oral forms of hormone. Low risk of contraceptive failure. Use Caution/Monitor.sulfamethoxazoleMonitor Closely (1)sulfamethoxazole will decrease the level or effect of mestranol by altering intestinal flora. Applies only to oral forms of hormone. Low risk of contraceptive failure. Use Caution/Monitor.sulfamethoxypyridazineMonitor Closely (1)sulfamethoxypyridazine decreases effects of mestranol by unspecified interaction mechanism. Use Caution/Monitor.sulfisoxazoleMonitor Closely (1)sulfisoxazole will decrease the level or effect of mestranol by altering intestinal flora. Applies only to oral forms of hormone. Low risk of contraceptive failure. Use Caution/Monitor.tacrolimusMonitor Closely (1)tacrolimus will increase the level or effect of mestranol by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.tazemetostatMonitor Closely (2)tazemetostat will decrease the level or effect of mestranol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. mestranol will increase the level or effect of tazemetostat by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.tecovirimatMonitor Closely (1)tecovirimat will decrease the level or effect of mestranol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Tecovirimat is a weak CYP3A4 inducer. Monitor sensitive CYP3A4 substrates for effectiveness if coadministered.teicoplaninMonitor Closely (1)teicoplanin will decrease the level or effect of mestranol by altering intestinal flora. Applies only to oral forms of hormone. Low risk of contraceptive failure. Use Caution/Monitor.temocillinMonitor Closely (1)temocillin will decrease the level or effect of mestranol by altering intestinal flora. Applies only to oral forms of hormone. Low risk of contraceptive failure. Use Caution/Monitor.tetracyclineMonitor Closely (1)tetracycline will decrease the level or effect of mestranol by altering intestinal flora. Applies only to oral forms of hormone. Low risk of contraceptive failure. Use Caution/Monitor.ticarcillinMonitor Closely (1)ticarcillin will decrease the level or effect of mestranol by altering intestinal flora. Applies only to oral forms of hormone. Low risk of contraceptive failure. Use Caution/Monitor.tigecyclineMonitor Closely (1)tigecycline will decrease the level or effect of mestranol by altering intestinal flora. Applies only to oral forms of hormone. Low risk of contraceptive failure. Use Caution/Monitor.tinidazoleMonitor Closely (1)mestranol will increase the level or effect of tinidazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.tipranavirSerious - Use Alternative (2)tipranavir will increase the level or effect of mestranol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. tipranavir decreases levels of mestranol by increasing metabolism. Avoid or Use Alternate Drug. May result in contraceptive failure.tizanidineMinor (1)mestranol increases levels of tizanidine by unspecified interaction mechanism. Minor/Significance Unknown.tobramycinMonitor Closely (1)tobramycin will decrease the level or effect of mestranol by altering intestinal flora. Applies only to oral forms of hormone. Low risk of contraceptive failure. Use Caution/Monitor.tolvaptanMonitor Closely (1)tolvaptan will increase the level or effect of mestranol by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.topiramateMonitor Closely (1)topiramate will decrease the level or effect of mestranol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.tranexamic acid injectionMonitor Closely (1)tranexamic acid injection, mestranol. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Increased risk of thromboembolic disorder.tranexamic acid oralContraindicated (1)tranexamic acid oral, mestranol. Either increases toxicity of the other by pharmacodynamic synergism. Contraindicated. Coadministration of tranexamic acid oral and combination hormonal contraceptives increases thrombotic risk .trazodoneMonitor Closely (1)trazodone will decrease the level or effect of mestranol by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.Minor (1)mestranol, trazodone. Mechanism: unspecified interaction mechanism. Minor/Significance Unknown. Estrogens and progestins may decr tricyclic antidepressant effects, while increasing TCA plasma concentration and adverse effects.trimethoprimMonitor Closely (1)trimethoprim will decrease the level or effect of mestranol by altering intestinal flora. Applies only to oral forms of hormone. Low risk of contraceptive failure. Use Caution/Monitor.trimipramineMinor (1)mestranol, trimipramine. Mechanism: unspecified interaction mechanism. Minor/Significance Unknown. Estrogens and progestins may decr tricyclic antidepressant effects, while increasing TCA plasma concentration and adverse effects.tucatinibSerious - Use Alternative (1)tucatinib will increase the level or effect of mestranol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid concomitant use of tucatinib with CYP3A substrates, where minimal concentration changes may lead to serious or life-threatening toxicities. If unavoidable, reduce CYP3A substrate dose according to product labeling.ursodiolMinor (1)mestranol decreases effects of ursodiol by pharmacodynamic antagonism. Minor/Significance Unknown.vancomycinMonitor Closely (1)vancomycin will decrease the level or effect of mestranol by altering intestinal flora. Applies only to oral forms of hormone. Low risk of contraceptive failure. Use Caution/Monitor.verapamilMonitor Closely (2)verapamil will increase the level or effect of mestranol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. verapamil will increase the level or effect of mestranol by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.voriconazoleMonitor Closely (1)voriconazole will increase the level or effect of mestranol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.voxelotorSerious - Use Alternative (1)voxelotor will increase the level or effect of mestranol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Voxelotor increases systemic exposure of sensitive CYP3A4 substrates. Avoid coadministration with sensitive CYP3A4 substrates with a narrow therapeutic index. Consider dose reduction of the sensitive CYP3A4 substrate(s) if unable to avoid.zafirlukastMonitor Closely (1)zafirlukast will increase the level or effect of mestranol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Frequency Not Defined Common Emotional lability Headache Breast symptoms Menstrual cramps Abdominal pains Nausea Serious Arterial/venous thromboembolism Hypertension MI Cerebral hemorrhage Gallbladder disease Hepatic adenoma Black Box Warnings Cigarette smoking & risk of cardiovascular disease Cigarette smoking increases risk of serious cardiovascular adverse effects from combination hormonal contraceptive use This risk increases w/ age (>35 yr) & with heavy smoking (15 or more cigarettes/day) Advise women who use hormonal oral contraceptives not to smoke Contraindications Documented hypersensitivity Active or history of