Where does the tirzepatide (Mounjaro) prescribing information indicate that an enteric‑coated oral contraceptive was used in the drug‑interaction study?

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Tirzepatide Drug Interaction Study: Oral Contraceptive Formulation

Location of Enteric-Coated Contraceptive Information

The tirzepatide prescribing information does not explicitly state that an enteric-coated oral contraceptive was used in the drug-interaction study. The available evidence describes the contraceptive formulation used in the pharmacokinetic study but does not specify enteric coating. 1

What the Prescribing Information Actually States

Contraceptive Formulation Details

  • The tirzepatide drug-interaction study evaluated a combined oral contraceptive containing ethinyl estradiol and norgestimate, which are the active hormonal components tested for pharmacokinetic interactions. 1

  • The study demonstrated statistically significant reductions in area under the plasma drug concentration-time curve (AUC), maximum concentration (Cmax), and time to maximum plasma concentration (Tmax) when tirzepatide was co-administered with the oral contraceptive, indicating meaningful pharmacokinetic interference. 1

Mechanism of Interaction

  • Tirzepatide causes substantially greater gastric emptying delay compared to typical GLP-1 receptor agonists due to its dual GIP/GLP-1 receptor mechanism, which is the primary driver of the oral contraceptive interaction. 1

  • The gastric emptying delay is most pronounced after the first dose of tirzepatide, with subsequent tachyphylaxis developing over time, though the interaction remains clinically relevant throughout treatment. 1

Clinical Implications

Prescribing Guidance

  • Women using oral contraceptives should switch to non-oral contraceptive methods or add barrier contraception for 4 weeks after tirzepatide initiation and after each dose escalation, as recommended in the tirzepatide prescribing information to account for the absorption interference. 2

  • This precaution is unique to tirzepatide among incretin-based therapies, as GLP-1 receptor agonists alone (semaglutide, liraglutide, dulaglutide) have not demonstrated clinically significant interactions with oral contraceptives in formal studies. 1

Contrast with GLP-1 Receptor Agonists

  • Five separate clinical trials of GLP-1 receptor agonists (without GIP co-agonism) showed no statistically or clinically significant impact on oral contraceptive pharmacokinetics, distinguishing them from tirzepatide's interaction profile. 1

  • The rapid dose escalation protocol and greater gastric emptying delay with tirzepatide enhanced the impact on oral medication absorption, creating a unique interaction not observed with standard GLP-1 monotherapy. 1

Common Pitfall to Avoid

Do not assume the contraceptive formulation was enteric-coated based on the interaction data alone—the prescribing information describes the hormonal components (ethinyl estradiol/norgestimate) but does not specify pharmaceutical coating technology. The interaction is driven by tirzepatide's gastric effects rather than by any special contraceptive formulation. 1

References

2
Guideline

Converting from Ozempic (Semaglutide) to Zepbound (Tirzepatide)

Praxis Medical Insights: Practical Summaries of Clinical Guidelines, 2025

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Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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