Mounjaro Prescribing Guide

---
name: mounjaro-prescribing-guide
description: Bedside prescribing reference for Mounjaro (tirzepatide) — indications, dose escalation, missed-dose rule, KwikPen vs prefilled pen differences, contraindications, warnings, storage, and monitoring. Use when a clinician asks how to start tirzepatide, how to titrate Mounjaro, how to handle a missed weekly dose, Mounjaro storage, Mounjaro contraindications, Mounjaro pregnancy/MTC warnings, or needs a quick Mounjaro monograph lookup. Grounded in the Canadian Product Monograph (Eli Lilly Canada, April 2026).
---

# 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

| Step | Dose | Minimum duration |
|---|---|---|
| Start | 2.5 mg s.c. once weekly | 4 weeks (initiation — not for glycemic control) |
| Step up | 5 mg weekly | ≥ 4 weeks |
| Further | +2.5 mg every ≥ 4 weeks | as needed |
| Max | 15 mg weekly | — |

- 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

| Feature | Single-dose pen/vial | KwikPen (multi-dose) |
|---|---|---|
| Doses per device | 1 | 4 |
| Preservative | None | Benzyl alcohol 5.4 mg/0.6 mL + phenol |
| Monthly devices | 4 | 1 |
| Discard after | Single use | 4 weekly doses |
| Unrefrigerated storage | Up to **21 days** at ≤ 30°C | Up to **30 days** at ≤ 30°C |

**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.