Mounjaro Prescribing Guide

Mounjaro (Tirzepatide) — Prescribing Guide

Indication

Adjunct to diet and exercise for glycemic control in adult T2D.

• Monotherapy (if metformin inappropriate)
• With metformin ± SU, with metformin ± SGLT2i, or with basal insulin ± metformin
• Not for T1D, DKA, combination with short/medium-acting or dual insulin
• Not indicated for pediatrics (< 18 y)

Contraindications

• Personal/family history of MTC or MEN-2
• Pregnancy (contraindicated)
• Hypersensitivity to tirzepatide or excipients (incl. benzyl alcohol in KwikPen)

Dose Escalation

• Any day, any time, with or without meals.
• Inject abdomen, thigh, or upper arm — rotate sites.
• Never IM or IV; never mix with insulin (separate injections).
• No dose adjustment for renal or hepatic impairment or age ≥ 65. Not recommended in ESRD.

Missed Dose

• Within 4 days (96 h) of missed dose → administer ASAP; resume schedule.
• > 4 days → skip; resume on regularly scheduled day.
• To change weekly day: ≥ 72 h must separate two doses.

KwikPen vs Single-Dose Pen/Vial

Hepatic or renal impairment + KwikPen: inform patient of metabolic acidosis risk from benzyl alcohol accumulation — prefer single-dose if concerned.

Storage

• Refrigerate 2–8°C until expiry.
• Do not freeze. If frozen → discard.
• Protect from light (original carton).
• Discard used pens in puncture-resistant container.

Key Warnings

• Thyroid C-cell tumours (black-box): counsel on neck mass, dysphagia, dyspnea, hoarseness. Routine calcitonin/US monitoring not recommended.
• Gastrointestinal AEs (see glp1-gi-ae-symptom-advisor + glp1-dose-escalation-troubleshooter).
• Severe gastroparesis — not studied; caution / consider dose modification / discontinuation.
• Malnutrition — reported including severe/fatal; consider nutritional supplementation; discontinue if severe/persistent.
• Acute pancreatitis (0.2% in trials) — see glp1-pancreatobiliary-risk-monitor. Not evaluated in prior AP — caution.
• Acute gallbladder disease (0.6%) — cholelithiasis/cholecystitis/cholecystectomy.
• Acute kidney injury via dehydration from GI AEs — monitor renal function during dose escalation if severe GI reactions.
• Diabetic retinopathy — rapid glucose correction may transiently worsen; caution in proliferative/macular edema.
• Heart rate increase 2–4 bpm mean; caution in patients where HR rise could worsen cardiac status. No NYHA IV experience.
• Pulmonary aspiration under GA / deep sedation — see glp1-perioperative-aspiration.
• Suicidal ideation — monitor for mood changes.
• Hypersensitivity / anaphylaxis / angioedema — discontinue if occurs.

Monitoring

• HbA1c for long-term glycemic response.
• Self-monitored glucose only needed when combined with SU/insulin.
• Monitor renal function if severe GI AEs with dehydration.
• Refer to endocrinology if thyroid nodules found incidentally or serum calcitonin elevated.

Special Populations

• Elderly ≥ 65: no dose adjustment; 30% of trial pop was ≥ 65, 4% ≥ 75.
• Pregnancy: contraindicated. Discontinue ≥ 1 month before planned pregnancy (long half-life ~5 days).
• Breastfeeding: very low milk transfer; individualise risk/benefit.
• Oral contraceptives: reduced absorption — use non-oral contraception or add barrier method for 4 weeks after initiation AND for 4 weeks after each dose escalation. See glp1-oral-contraceptive-interaction.

Drug Combinations Requiring Dose Reduction

• Sulfonylurea / basal insulin → reduce dose to lower hypoglycemia risk (trial reduced baseline insulin by 20%). See glp1-insulin-su-dose-reduction.
• Other incretin drugs (GLP-1 RA, DPP-4i) → do not combine.

Overdose

Expected symptom: GI (nausea). Supportive care; prolonged observation due to long half-life.

Reference

MOUNJARO Product Monograph, Eli Lilly Canada, authorised 2026-04-02. Control #301221.