Our understanding of the potential side effects associated with weight loss drugs remains incomplete. For individuals contemplating the use of tirzepatide, an alternative contraceptive method is advised over oral contraceptive pills due to the medication’s potential to diminish their effectiveness.
Certain drugs commonly prescribed for managing type 2 diabetes and obesity may lead to unintended side effects. In particular, tirzepatide, marketed as Mounjaro, has been identified with a cautionary note regarding birth control pills, indicating a potential reduction in their efficacy.
The U.S. Food and Drug Administration (FDA) has issued a warning suggesting that individuals utilizing oral contraceptives consider transitioning to a different form of birth control or adopt a barrier method for four weeks following the initiation of tirzepatide, as well as for four weeks after any subsequent dosage increments.
Despite these precautions, significant gaps persist in our knowledge regarding how certain weight loss drugs may interfere with the effectiveness of birth control pills. Furthermore, the specific association of a warning related to birth control with tirzepatide, as opposed to other drugs in the same category, remains a subject of uncertainty and warrants further investigation.
“There are a lot of unknowns and the data we have can answer some questions but not all,” Beverly Tchang, MD, an endocrinologist at Weill Cornell Medicine’s Iris Cantor Women’s Health Center in New York, said.
Weight Loss Drugs and Birth Control Pills Absorption
Among the widely used weight loss drugs, namely tirzepatide, Ozempic, and Wegovy, only Wegovy has received FDAapproval explicitly for weight loss. While tirzepatide and Ozempic are sanctioned for managing type 2 diabetes, they are frequently prescribed off-label for weight loss.
Categorized as dual agonist (tirzepitide or Mounjaro) and semaglutide (Wegovy and Ozempic), these drugs operate in similar yet distinct ways. They induce the production of specific hormones associated with appetite and satiety, mimicking the body’s natural response after eating. By artificially introducing these hormones, these medications slow down the digestive process, prolonging the feeling of fullness.
The potential impact of these drugs on the absorption of oral medications, particularly contraceptives, remains a theoretical concern. For instance, with tirzepatide, being a dual agonist acting on both glucagon-like peptide (GLP) and glucose-dependent insulinotropic polypeptide (GIP), there may be specific concerns. On the other hand, semaglutide medications exclusively act on GLP.
Despite these theoretical considerations, no conclusive studies have confirmed whether these weight loss drugs indeed affect the absorption of oral medications, including contraceptives. Sarah Mcbane, PharmD, an expert in women’s health and associate dean of pharmacy education at the University of California in Irvine, suggests that the warning regarding contraceptives, particularly for tirzepatide, might be a precaution due to its dual agonist nature.
While the precise impact on oral medication absorption remains unclear, these weight loss drugs come with general warnings about their potential interactions with oral medications. Thus, caution is advised in the absence of conclusive evidence regarding the specific effects on contraceptive efficacy or other oral medications.
“The prescribing information for all of these medications states that there is the potential to affect the absorption and efficacy of oral medications,” said Dr. McBane. She also said that at least one study has shown that semaglutide does not have a significant on the impact blood levels of the hormones that are found in birth control pills.
The preceding research, which was published in 2015 in the Journal of Clinical Pharmacology, involved a cohort of 43 women concurrently using semaglutide and combined oral contraceptives. The study aimed to assess hormonal changes by measuring hormone levels eight days prior to the initiation of semaglutide and 13 weeks thereafter. Interestingly, after this 13-week period, during which participants were administered 1 milligram of semaglutide per week, researchers observed no significant decreases in ethinylestradiol or levonorgestrel. These two hormones are integral components of common birth control pills.
Birth control pill interaction warnings are not listed on Wegovy or Ozempic’s labels. However, “they did not measure these levels during dose escalation, which is how the manufacturer of Mounjaro assessed medication interaction,” Dr. Tchang said
Eli Lilly, the manufacturer of Mounjaro, concluded a human clinical trial last year specifically examining the drug’s impact on birth control pills at various stages of dosage escalation. However, the results of this trial are still pending release. Currently, the available data on how the drug may affect oral contraceptives is limited, but it is indicated as safe on the drug’s label.
It’s important to note that each pharmaceutical company assessed the impact of their respective drugs on birth control pills using different methodologies. Consequently, the recommendations provided by these companies are based on distinct sets of data. Tchang emphasized that individuals need to be on these medications for approximately four weeks before experiencing their full effects, a period referred to as steady state.
Eli Lilly assessed the potential impact on birth control pills before reaching steady state, while Novo Nordisk, the manufacturer of Wegovy and Ozempic, measured the effects after achieving steady state. Both companies can only offer recommendations based on their specific data, which did not measure the same aspects of drug interaction.
“We’re working with incomplete information,” Tchang stated. “That’s potentially why we have two different answers to the same question.”
Tchang observed that the medications operate in slightly distinct manners, and this variation might contribute to why one includes a caution regarding the effectiveness of birth control pills, while the others do not.
Still, most of her patients believe in these and that the benefits that come with weight loss medication still outweigh the potential risks. “Every doctor and patient needs to have an in-depth conversation about all of the nuances of risk or potential risks,” Tchang added.
Should You Stop Taking Weight Loss Medications if You Are on Birth Control?
In summary, McBane advises against discontinuing tirzepatide if you have concerns about becoming pregnant.
“Someone who is taking or thinking about taking tirzepatide should consider switching to a contraceptive other than the pill,” she said. She also added that there are many options for birth control, so the fact that tirzepatide may make oral methods not as effective shouldn’t discourage people from taking these. “The specific method will really depend on that individual’s preferences and reason for using the contraceptive.”
Although birth control patches, rings, injections, implants, and intrauterine devices (IUDs) do not carry any risk of being affected by taking tirzepatide or semaglutide. “It is always a good idea to use a backup form of birth control, but especially since we do not have data on how these medications can affect pregnancy,” Tchang said.