Tirzepatide

WHAT IT DOES

Tirzepatide is a single engineered peptide that activates two incretin receptors at once, the GIP receptor and the GLP-1 receptor. Both receptors sit on pancreatic beta cells, where activation raises insulin secretion only when glucose is elevated, and both are expressed in brain regions that regulate appetite and food intake. Across the SURPASS program the dual mechanism produced HbA1c reductions of 1.24 to 2.58% and body weight reductions of 5.4 to 11.7 kg at 5-15mg weekly, larger than a selective GLP-1 receptor agonist comparator (Nauck 2022, PMID: 36050763).

The third effect is the one that matters most for anything you swallow. Tirzepatide slows gastric emptying, and it does so more strongly than typical GLP-1 receptor agonists. The delay is most substantial after the first dose and then undergoes tachyphylaxis with subsequent doses, a pattern described in a review of tirzepatide and oral hormonal contraception, which also notes that rapid dose escalation enhances the impact on oral drugs (Skelley 2023, PMID: 37940101). Practically, food and capsules sit in the stomach longer, arrive at the small intestine later, and arrive at a different concentration profile. That single mechanism drives the nausea, the early fullness, the constipation, the oral contraceptive interaction, and the residual gastric content finding, and it is why timing advice on this page is mechanical rather than mystical.

SAFETY PROFILE

Critical Interactions (Do Not Combine Without Medical Supervision)

Moderate Interactions (Monitor Closely)

Theoretical/Low-Risk Interactions