Levonorgestrel and ethinyl estradiol and Phentermine and topiramate interaction
Levonorgestrel and ethinyl estradiol and Phentermine and topiramate: both prescribing labels describe an interaction that usually calls for monitoring, a dose change, or spacing the doses.
Usually manageable with monitoring or a dose change. Tell your pharmacist you take both.
What the FDA labels say
From the Levonorgestrel and ethinyl estradiol (Tyblume) label · effective 2026-08-27
Enzyme inducers (e.g., CYP3A4) : May decrease the effectiveness of TYBLUME or increase breakthrough bleeding.
Metabolic Enzyme Inducers Clinical effect Concomitant use of CHCs with metabolic enzyme inducers may decrease the plasma concentrations of the estrogen and/or progestin component of CHCs [see Clinical Pharmacology (12.3) ] .
Examples Aprepitant, barbiturates, bosentan, carbamazepine, efavirenz, felbamate, griseofulvin, oxcarbazepine, phenytoin, rifampin, primidone, phenylbutazone, rifabutin, rufinamide, topiramate, products containing St.
Counsel patients to use a back-up or alternative method of contraception when enzyme inducers are used with TYBLUME.
Prevention or management Counsel females to use an alternative method of contraception or a backup method when enzyme inducers are used with CHCs.
From the Phentermine and topiramate label · effective 2026-05-18
Oral Contraceptives Clinical Impact Co-administration of multiple-dose phentermine and topiramate extended-release capsules 15 mg/92 mg once daily with a single dose of oral contraceptive containing 35 µg ethinyl estradiol (estrogen component) and 1 mg norethindrone (progestin component), in obese otherwise healthy volunteers, decreased the exposure of ethinyl…
Although this interaction is not anticipated to increase the risk of pregnancy, irregular bleeding (spotting) may occur more frequently due to both the increased exposure to the progestin and lower exposure to the estrogen, which tends to stabilize the endometrium.
Oral Contraceptives : Altered exposure of progestin and estrogen may cause irregular bleeding, but not increased risk of pregnancy.
Intervention Inform patients not to discontinue their combination oral contraceptive if spotting occurs, but to notify their health care provider if the spotting is troubling to them.
Advise patients not to discontinue oral contraceptives if spotting occurs ( 7 ).
Taking more than these two? Interactions stack. Check your whole list at once; it stays in your browser.
Open in the checkerNot medical advice. Interaction Checker quotes FDA label text and NIH fact sheets. Whether an interaction matters for you depends on doses, timing, kidney and liver function, and other conditions. Confirm with a pharmacist or prescriber.