Opioid

Morphine

Natural μ-agonist

Mechanism: μ-opioid receptor agonist.

Calculate dose for your patient

Enter weight (kg or lb). Always verify before administration.

Patient weight

Computed weight

70.0 kg · 154.3 lb

Post-op analgesia

3.5 mg – 7.0 mg

= 3.50–7.00 mL (1 mg/mL)

Exceeds typical adult max 5 mg — cap and reassess.

Histamine release; avoid M6G accumulation in renal failure.

Weight is saved on this device for the next calculator you open.

Full dose calculator

Onset

5–10 min IV

Duration

3–4 h IV; up to 24 h intrathecal

Metabolism

Hepatic glucuronidation → M6G (active, renally cleared).

Dosing

Adult

IV: 2–4 mg q4h PRN. Neuraxial: intrathecal 100–300 mcg; epidural 2–5 mg.

Pediatric

0.05–0.1 mg/kg IV.

Indications

Post-op pain
Neuraxial analgesia (Duramorph)

Contraindications

Renal failure (caution — M6G accumulates)

Side Effects

Histamine release / hypotension
Pruritus
PONV
Constipation
Delayed respiratory depression with neuraxial

Clinical Pearls

1Monitor 24 h for delayed respiratory depression after intrathecal morphine.

References & Further Reading

1
Textbook
Flood P, Rathmell JP, Shafer S. Stoelting's Pharmacology and Physiology in Anesthetic Practice. 5th ed. Philadelphia: Wolters Kluwer; 2015.
2
Textbook
Gropper MA, Miller RD, Cohen NH, et al., eds. Miller's Anesthesia. 9th ed. Philadelphia: Elsevier; 2020.
3
Textbook
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC, Ortega R, Sharar SR, Holt NF. Clinical Anesthesia. 8th ed. Philadelphia: Wolters Kluwer; 2017.
4
Textbook
Adriano A, Morris R, eds. 2021 CA-1 Tutorial Textbook (15th Ed.). Stanford University Medical Center, Department of Anesthesiology.

Citations are provided to direct further study. Always check the most current edition of guidelines and society recommendations — the information in this chapter is a teaching summary, not primary source material.