tirzepatide (Mounjaro)

General Information

Mounjaro is a once-weekly injectable form of tirzepatide, a dual GIP/GLP-1 receptor agonist indicated for type 2 diabetes (label).

It is not a psychiatric medication. In psychiatric practice, it is most often considered when diabetes/obesity complicate care or when cardiometabolic risk from weight-gain–promoting psychotropics is clinically limiting (clinical).

A high-impact practical warning is reduced efficacy of oral hormonal contraceptives during initiation and dose escalation due to delayed gastric emptying; contraception counseling should be explicit and proactive (label).

The compare view, evidence feed, and print page help compare titration schedules and monitoring themes.

In psychiatric populations, feasibility often depends on coverage, follow-up capacity during titration, and coordination across prescribers (especially when diabetes medications need adjustment). GI tolerability and hydration planning can be critical to avoid destabilizing adherence to psychotropics (clinical).

Mechanism of Action

Refer to the Glossary entry on Neurotransmitters for background on receptor systems involved in serious mental illness.

Tirzepatide is a dual GIP and GLP-1 receptor agonist. Clinically it improves glycemic control and supports weight loss through incretin-based metabolic signaling, appetite effects, and delayed gastric emptying (label/clinical).

In mental health care, the most common rationale is metabolic risk reduction while maintaining psychiatric stability and medication adherence (clinical).

• Dual GIP/GLP-1 receptor agonism (incretin-based metabolic signaling).
• Appetite and satiety effects (clinical framing).

Metabolism and Pharmacokinetics

• Long half-life supports once-weekly dosing (approximately 5 days per labeling conventions).
• Major CYP-mediated interactions are not expected (peptide metabolism), but delayed gastric emptying can affect absorption of some oral drugs during initiation and dose escalation (label/clinical).

Dosing and Administration

• Typical: 5–15 mg subcutaneously once weekly after titration (start 2.5 mg once weekly for 4 weeks, then 5 mg once weekly; increase in 2.5 mg steps at 4-week intervals if needed) (label).
• If a dose is missed, administer as soon as possible within 4 days (96 hours); if more than 4 days have passed, skip the missed dose and resume the regular schedule. Do not take two doses within 3 days of each other (label).
• Injection sites include abdomen, thigh, or upper arm; rotate sites (label).
• GI tolerability often improves with slower escalation, smaller meals, and attention to hydration; severe vomiting warrants evaluation for dehydration and rare complications (clinical).

Monitoring & Labs

• Weight/BMI and metabolic parameters (HbA1c/fasting glucose) when clinically indicated; coordinate diabetes regimen changes across prescribers (clinical).
• Monitor for symptoms of pancreatitis and gallbladder disease (persistent severe abdominal pain, vomiting) (label).
• Monitor for dehydration and renal function concerns when significant GI losses occur (label/clinical).
• Contraception counseling for patients using oral hormonal contraceptives during initiation and dose escalation (label).
• Screen for disordered eating and monitor for excessive appetite suppression when weight-loss goals could be unsafe (clinical).

Consider coordination with primary care/endocrinology for diabetes and cardiovascular risk management; avoid siloed medication changes (clinical).

Adverse Effects

Interactions

• Oral hormonal contraceptives: advise patients to switch to a non-oral contraceptive method or add a barrier method for 4 weeks after initiation and for 4 weeks after each dose escalation (label).
• Hypoglycemia risk increases when combined with insulin or sulfonylureas; coordinate dose adjustments with the diabetes prescriber (label/clinical).
• Delayed gastric emptying can affect absorption of some oral medications during titration; review narrow-therapeutic-index agents and time-sensitive regimens (clinical).

Other Useful Information

• In serious mental illness care, the key trade-off is often metabolic benefit vs feasibility. Stabilizing nausea, hydration, and follow-up can prevent downstream adherence problems with psychiatric medications (clinical).

References

1. MOUNJARO (tirzepatide) injection prescribing information — DailyMed (2026)
2. Tirzepatide versus semaglutide once weekly in patients with type 2 diabetes — New England Journal of Medicine (2021)
3. Tirzepatide once weekly for the treatment of obesity — New England Journal of Medicine (2022)
4. Therapeutic Management OF Atypical Antipsychotic Related Metabolic Dysfunctions Using GLP 1 Receptor Agonists: A Systematic Review — Experimental and Therapeutic Medicine (2023)