Does Phentermine And Topiramate Interact with Norethindrone And Ethinyl Estradiol?
Phentermine And Topiramate and Norethindrone And Ethinyl Estradiol have a moderate drug interaction according to U.S. FDA drug labeling data. Co-administration decreased ethinyl estradiol exposure by 16% and increased norethindrone exposure by 22%, potentially causing irregular bleeding/spotting. The mechanism involves altered pharmacokinetics of oral contraceptive components. Patients taking both medications should consult their healthcare provider before starting, stopping, or changing the dosage of either drug. This information is based on official FDA drug labeling sourced from OpenFDA and the NIH National Library of Medicine.
- Severity
- Moderate
- Phentermine And Topiramate Class
- Cytochrome P450 3A4 Inducers
- Norethindrone And Ethinyl Estradiol Class
- Estrogen
- Management
- Monitor for effects
- Data Source
- U.S. FDA via OpenFDA
How This Interaction Works
The interaction between Phentermine And Topiramate and Norethindrone And Ethinyl Estradiol occurs because altered pharmacokinetics of oral contraceptive components. Clinically, this means co-administration decreased ethinyl estradiol exposure by 16% and increased norethindrone exposure by 22%, potentially causing irregular bleeding/spotting. This is classified as a moderate interaction. While it may not require stopping either medication, your healthcare provider should be aware you are taking both so they can monitor for potential effects and adjust treatment if necessary.
What To Tell Your Doctor or Pharmacist
If you are taking Phentermine And Topiramate and your doctor is considering prescribing Norethindrone And Ethinyl Estradiol (or vice versa), make sure to:
- Inform your doctor and pharmacist of all current medications, including over-the-counter drugs and supplements
- Ask whether the benefits of combining these medications outweigh the risks for your specific situation
- Ask what symptoms to watch for that would indicate the interaction is causing problems
- Ask whether any dosage adjustments are needed
- Never stop or change either medication without first consulting your healthcare provider