Tirzepatide
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Tirzepatide
Mounjaro (T2DM), Zepbound (obesity, OSA)
Tirzepatide is the first dual GIP / GLP-1 receptor agonist ("twincretin") approved for clinical use. Eli Lilly markets it as Mounjaro (for type 2 diabetes mellitus, FDA-approved May 2022)[1] and Zepbound (for obesity, November 2023;[2] later expanded to obstructive sleep apnea in obesity in December 2024[4]).
In direct comparison, tirzepatide produced greater HbA1c reduction and greater weight loss than semaglutide at maximum approved doses (SURPASS-2),[5] and the largest weight loss yet reported with an injectable incretin in obesity without diabetes, up to ~22.5% body weight at 72 weeks (SURMOUNT-1).[3]
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Avoid. Animal embryofetal toxicity is documented.[1] Discontinue ≥1 month before planned conception. Clinically important interaction: tirzepatide reduces absorption of oral contraceptives during initiation and dose escalation, counsel patients to switch to a non-oral or barrier method for at least the first 4 weeks of each new dose level.[1]
GLP-1 receptor agonist · Semaglutide · Liraglutide · Dulaglutide · Exenatide · Type 2 diabetes mellitus · Obesity · Obstructive sleep apnea
Experience
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Problems
Titration strategies
Mounjaro, standard T2DM titration0
2.5 mg SC weekly × 4 weeks (non-therapeutic ramp)
→ 5 mg SC weekly × ≥4 weeks → 7.5 mg weekly × ≥4 weeks if needed → 10 mg weekly × ≥4 weeks if needed → 12.5 mg weekly × ≥4 weeks if needed → 15 mg weekly (max)[1]
Hold at any tolerated dose if response is adequate. Slow titration is preferred in any patient with significant GI symptoms, holding 8–12 weeks before advancing is reasonable.Zepbound, standard obesity titration0
2.5 mg SC weekly × 4 weeks (non-therapeutic ramp)
→ 5 mg SC weekly × ≥4 weeks → 7.5 mg → 10 mg → 12.5 mg → 15 mg weekly (max), each step held ≥4 weeks[2]
Maintenance is generally 5, 10, or 15 mg/wk depending on response and tolerability. The intermediate steps (7.5 / 12.5 mg) exist to ease titration but are not typical maintenance doses.Effects
- Early satiety and reduced food intake[3]
- Food noise quieting (also reported with semaglutide)[citation needed]
- Nausea, dose-dependent, worst during titration steps[1]
- Constipation or diarrhea (variable)[1]
- Decreased appetite (clinically the desired effect)[1]
- Injection-site reactions, uncommon, generally mild[1]
GI tolerability appears modestly better than selective GLP-1 RAs at comparable HbA1c / weight-loss endpoints,[citation needed] possibly reflecting the additional GIP-receptor activity.
Pharmacokinetics
Chemistry. 39-amino-acid synthetic peptide; dual agonist at the GIP receptor and GLP-1 receptor. Acylated with a C20 fatty diacid linked via γGlu-2×AEEA spacer for albumin binding → ~5-day half-life enabling weekly dosing.[6]
Acylation with a C20 fatty diacid drives non-covalent albumin binding, producing a terminal half-life of ~120 hours and supporting once-weekly subcutaneous dosing.[6][1] Cleared predominantly by proteolytic catabolism; no CYP-mediated metabolism. Renal and hepatic impairment do not require dose adjustment.[1]
Delayed gastric emptying is greatest during dose escalation and attenuates over time. This can reduce absorption of co-administered oral medicines, including oral contraceptives, clinically relevant during the first 4 weeks of any new dose level.[1]Pharmacodynamics
Receptor pharmacology. Activates both GIP and GLP-1 receptors. The dual mechanism produces greater glucose-dependent insulin secretion, greater weight loss, and a somewhat improved GI tolerability profile relative to selective GLP-1 RAs in head-to-head comparison.[6][5]
At the 15 mg/wk maintenance dose:
- HbA1c reduction of ~2.0–2.3 percentage points in T2DM[5]
- Weight loss of ~22.5% body weight at 72 wk in obesity without T2DM (SURMOUNT-1)[3]
- In T2DM with obesity, ~15.7% weight loss at 72 wk (SURMOUNT-2)[7]
- In moderate-to-severe OSA with obesity, ~50% reduction in apnea–hypopnea index at 52 wk (SURMOUNT-OSA)[4]
Interactions
No interactions reported yet.
Pregnancy and lactation
Monitoring
- Baseline: HbA1c, weight, BP, renal function, lipid panel
- Personal or family history of MTC or MEN2, contraindicated, do not start[1]
- Every 3 months for first year: HbA1c, weight, GI tolerability, signs of pancreatitis or gallbladder disease[1]
- Annual: renal function, lipids
- Pre-procedure: hold weekly dose ≥7 days before any planned anesthesia (per ASA 2024 guidance)[8]
Patient counseling
- Slow titration is non-negotiable.
- Inject SC in abdomen, thigh, or upper arm; rotate sites.[1]
- GI side effects peak in the first 2–4 weeks of each new dose level, then attenuate.
- Oral contraceptives: switch to a non-oral / barrier method for at least 4 weeks after starting and after each dose escalation.[1]
- Hydrate aggressively (volume depletion → AKI is a real risk).[1]
- Resistance training during weight loss protects lean mass.[citation needed]
- If a weekly dose is missed: take within 4 days; if >4 days, skip and resume on the next regular day.[1]
- Surgery: hold dose 7 days pre-op and tell every anesthesiologist.[8]
- Pregnancy planning: stop ≥1 month before trying to conceive.[1]
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See also
References
- ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 1.12 1.13 1.14 1.15 1.16 1.17 1.18 1.19 1.20 1.21 1.22 1.23 1.24 1.25 US FDA. Mounjaro (tirzepatide) prescribing information. Eli Lilly. https://www.accessdata.fda.gov/drugsatfda_docs/label/2022/215866s000lbl.pdf
- ↑ 2.0 2.1 2.2 2.3 US FDA. Zepbound (tirzepatide) prescribing information. Eli Lilly. https://www.accessdata.fda.gov/drugsatfda_docs/label/2023/217806s000lbl.pdf
- ↑ 3.0 3.1 3.2 3.3 Jastreboff AM et al. (2022). Tirzepatide once weekly for the treatment of obesity (SURMOUNT-1). NEJM 387:205–16. doi:10.1056/NEJMoa2206038
- ↑ 4.0 4.1 Malhotra A, Grunstein RR, Fietze I et al. (2024). Tirzepatide for the treatment of obstructive sleep apnea and obesity (SURMOUNT-OSA). NEJM 391(13):1193–205. doi:10.1056/NEJMoa2404881
- ↑ 5.0 5.1 5.2 Frías JP et al. (2021). Tirzepatide versus semaglutide once weekly in patients with type 2 diabetes (SURPASS-2). NEJM 385(6):503–15. doi:10.1056/NEJMoa2107519
- ↑ 6.0 6.1 6.2 Coskun T, Sloop KW, Loghin C et al. (2018). LY3298176, a novel dual GIP and GLP-1 receptor agonist for the treatment of type 2 diabetes mellitus. Mol Metab 18:3–14. doi:10.1016/j.molmet.2018.09.009
- ↑ Garvey WT, Frias JP, Jastreboff AM et al. (2023). Tirzepatide once weekly for the treatment of obesity in people with type 2 diabetes (SURMOUNT-2). Lancet 402(10402):613–26. doi:10.1016/S0140-6736(23)01200-X
- ↑ 8.0 8.1 Kindel TL et al. (2024). Perioperative GLP-1 receptor agonist safety guidance. Surg Obes Relat Dis 20(12):1183–8.
Summary
Classes
Pharmacy
Starting dose
2.5 mg SC weekly × 4 wk (non-therapeutic ramp)[1]
Pharmacology
Routes
Subcutaneous (abdomen, thigh, upper arm)[1]
Onset
Glycemic effect within days; full weight effect over months[3]
Duration
~7 days (weekly dosing)[1]
Half-life
~5 days (~120 h)[1]
Bioavailability
SC ~80%[citation needed]
Pregnancy
Avoid. Discontinue ≥1 month pre-conception. May reduce oral contraceptive efficacy during titration.[1]
Legal status
Rx-only;[1] not a controlled substance
Purported mechanism
Dual agonist of the GIP receptor and GLP-1 receptor ("twincretin").