Something You Can Worry About Less: Interference and Hormonal Birth Control

For those of us without medical degrees, the inner biochemical workings of the body can seem confusing. When people choose to use hormonal methods of birth control⁠ -- that's the pill⁠ , patch, ring, injection or implant -- they are changing these biochemical processes and introducing new variables into the equation. When pregnancy⁠ prevention is at stake, confusion or misinformation about these chemical processes and changes can produce anxiety.

One of the most common questions we receive in our direct services at Scarleteen are about chemical interactions or interference with hormonal birth control, and concerns that other medications (or foods, drinks and other things) may render contraception⁠ ineffective. With lots of misleading, contradictory, or downright confusing information out⁠ there, we wanted to set the record straight (or queer⁠ , if that’s more your style!).

As always, if you have specific questions about birth control and your body, or about the other medications you take, ask your doctor or pharmacist. When you discuss birth control options with a provider, always be sure to give a complete medical history and list of medications, so they can let you know right at the start if you have any possible interactions you should know about.

What does NOT interfere with the efficacy of hormonal birth control?

  • The food or beverage you use to take your pill
  • The sulfa class of antibiotics, often prescribed for urinary tract infections (UTIs)

What MAY interfere with the efficacy of hormonal birth control?

  • Conditions that cause vomiting or diarrhea: If you are vomiting or having diarrhea (you have had a pattern, over more than a day, of loose, watery stools) your body may not absorb your pill completely, so you should use a backup method during and for at least one week after your symptoms subside.
  • Common antibiotics such as amoxicillin, ampicillin, ciprofloxacin, clarithromycin, doxycycline or metronidazole: Current research indicates that almost all antibiotics have no effect on the efficacy⁠ of hormonal birth control. However, much of this research has included sample sizes considered too small to detect a rare interaction that may occur in less than 1% of users. So if you are taking an antibiotic, your decision to take more precautions depends on how much risk you are or are not comfortable with. Keep in mind also that if you are taking an antibiotic, your body is probably also battling an infection⁠ , which makes you more susceptible to other infections like STIs. The bottom⁠ line: if you are someone who wants to minimize these risks as much as you can, consider using condoms as a backup, the only method that can protect you from infections and pregnancy: not just for a week or so after finishing your antibiotic regimen as doctors often suggest, but all the time, too.
  • Higher body weights or higher BMIs (a weight over 165 pounds, or a BMI over 27), or certain health conditions: Individual differences and certain environmental or bodily factors may affect the efficacy of hormonal birth control or increase its risks. Research remains unclear on which factors specifically pose a risk to users of various hormonal birth control methods, and to what extent. Backup/barrier methods are a great idea for anyone who wants to practice safer sex⁠ and keep pregnancy and STI⁠ risks low.
  • Warfarin (blood-thinner): Evidence about this interaction is inconsistent. Talk with your doctor about the safest and most effective methods for you, which may depend on the specific conditions for which you take warfarin. Additionally, birth control itself may impact the efficacy of this drug. Consult with your doctor if you think this is a concern for you.

What DOES interfere with the efficacy of hormonal birth control, or might hormonal methods interfere with the efficacy of?

  • The antibiotic rifampin, used to treat both latent and active tuberculosis (TB): Regimens for rifampin and similar drugs often last several months. Consult with your doctor about special considerations for sexual⁠ activity and contraception if you are being treated for TB.
  • Some antiepileptic/anticonvulsant drugs: Some drugs used to treat epilepsy, bipolar disorder and migraines interfere with hormonal birth control by increasing the body’s metabolism (aka the breakdown) of hormones⁠ in the pill. Ask your doctor if you are unsure if the particular medication you take interferes with hormonal contraceptives. If it does, don’t worry: there are several safe and effective hormonal birth control options that you can discuss with your doctor. Additionally, birth control itself may impact the efficacy of these drugs. Consult with your doctor if you think this is a concern for you.
  • St. John’s Wort: This popular natural remedy for mild to moderate depression increases the metabolism of hormonal birth control, which means that those who take it might experience breakthrough bleeding, and should always use a backup method.
  • Antiretrovirals (ARVs): Antiretroviral medications, used to treat HIV⁠ , decrease the level of hormone present in the blood for users of certain hormonal methods. If you take ARVs, talk to your doctor about your options in order to decide on a method that will work best for you. HIV-positive individuals should always use condoms or other barriers, in order to prevent HIV transmission to partners, and because HIV-positive people are more prone to infection with other STIs.
  • Troglitazone: This antidiabetic, antinflammatory drug reduces the concentration of hormone in the blood. Higher doses of hormone can be prescribed to compensate for this interaction.
  • Drugs that affect gastric pH interfere with ella, a particular brand of emergency contraception⁠ Antacids, proton pump inhibitors, and H2 antagonists, used to treat GERD, interfere with ella (and only ella). Another kind of EC should be used for people who take these drugs. These medications are not a problem with other methods of hormonal birth control. 

This article is intended as a brief and limited factsheet about the most common and relevant drug interactions with birth control. It is not as a substitute for expert medical advice. As long as your doctor and/or pharmacist are aware of all of the medications you take, they will almost certainly know to brief you on any potential interactions (contraindications, in medical parlance) between your medications, including hormonal birth control. Trust your doctor to provide you with accurate, thorough information about your medical conditions and the medications you take.

For Nerds Only: Bibliography

  • Ament, Paul W., John G. Bertolino and James L. Liszewski: Clinically Significant Drug Interactions. American Family Physician 61(6): 1745-1754.
  • Archer, Johanna S.M. and David F. Archer: Oral contraceptive efficacy and antibiotic interaction: A myth debunked. Journal of the American Academy of Dermatology 46(6): 917-923.
  • Back, DJ et al.: Interindividual Variation and Drug Interactions with Hormonal Steroid Contraceptives. Drugs 21(1):46-61.
  • Centers for Disease Control and Prevention: Tuberculosis (TB) Treatment. Division of Tuberculosis Elimination. Accessed May 6, 2015 at
  • DeRossi, SS and EV Hersh: Antibiotics and oral contraceptives⁠ . Dental Clinics of North America 46(4): 653-64.
  • Guirguis, AB, A Airee and D Cobb: Probable Drug Interaction Between Warfarin and Hormonal Contraceptives. The Annals of Pharmacotherapy 43(12):2096-2102.
  • Helms, Stephen E. et al.: Oral contraceptive failure rates and oral antibiotics. Journal of the American Academy of Dermatology 36(5): 705-710.
  • Lopez LM et al.: Hormonal contraceptives for contraception in overweight or obese women. Cochrane Database of Systematic Reviews, Issue 7. Accessed May 6, 2015
  • Robinsion, Jennifer A., Roxanne Jamshidi and Anne E. Burke: Contraception for the HIV-positive Woman: A Review of Interactions between Hormonal Contraception and Antiretroviral Therapy. Infectious Diseases in Obstetrics and Gynecology, vol. 2012, Article ID 890160. Accessed May 5, 2015
  • Royal College of Obstetricians and Gynecologists: Drug Interactions with Hormonal Contraception. Faculty of Sexual and Reproductive Healthcare Clinical Guidance. Accessed May 6, 2015
  • Thorne, Sara, Anne MacGregor, and Cetherine Nelson-Piercy: Risks of contraception and pregnancy in heart disease. Heart 92(10): 1520-1525.

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