Strong Opioid·Analgesia - Opioids

Morphine (IR/IV)

Severe acute/chronic pain, myocardial infarction, acute pulmonary oedema, palliative dyspnea

S8OPIOIDSevredol, Ordine (liquid)20 mg tabletTGA

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At a glance

Max Dose

Titrated

Half-life

2-4 h

High risk: Renal Tox

ACTIVE METABOLITES

Caution: Histamine

HIGH RISK

Cautions

Avoid / Cautions

Severe renal impairment (eGFR < 30), severe asthma, paralytic ileus. Pregnancy Category C.

Where it stands

Rapid Summary

Overview

The classical gold-standard mu-opioid agonist. Highly effective for severe pain and dyspnea (APO/palliative).

Clinical Focus

Morphine produces highly active toxic metabolites that rely 100% on the kidneys for clearance. Lethal if used in severe renal failure.

Bottom Line

Morphine (IR/IV) is the gold-standard strong opioid for severe acute pain and palliative care, but causes respiratory depression, histamine release, and accumulates active metabolites in renal failure.

Formulation & Access

Brand Names

Sevredol, Ordine (liquid)

Oral Routes

Tablets IR (10, 20 mg). Oral liquid (2 mg/mL, 10 mg/mL).

Parenteral

Ampoules (10 mg/1 mL) for IV / IM / SC.

Prescribing & PBS

Highly Restricted (S8).

Indications & Use

Primary

TGA

Severe acute/chronic pain, myocardial infarction, acute pulmonary oedema, palliative dyspnea.

Clinical Place

First-line IV opioid on the ward. Unmatched for reducing preload in cardiac emergencies.

Quick reference

Class & Role

Strong Opioid — The classical gold-standard mu-opioid agonist.

Route / Formulation

Tablets IR (10, 20 mg). Oral liquid (2 mg/mL, 10 mg/mL). (Sevredol, Ordine (liquid))

Usual Dose & Max

IV 2-5 mg bolus, repeat every 5-10 mins PRN until pain controlled. OR PO 5-10 mg (IR liquid/tablet) q4h PRN. Titrated to effect.

Key Indication Doses

Acute Severe Pain: IV 2-5 mg bolus, repeat every 5-10 mins PRN until pain controlled. OR PO 5-10 mg (IR liquid/tablet) q4h PRN. Acute Pulmonary Oedema: IV 2.5-5 mg STAT (Reduces preload via histamine release and blunts air hunger). Renal Impairment: If eGFR < 30, avoid Morphine entirely. Switch to Hydromorphone or Fentanyl to prevent neurotoxic metabolite accumulation.

Best Uses

Key Risks

Respiratory: Respiratory depression, apnoea. Renal/Neuro: M3G accumulation in CKD causes severe hyperalgesia, massive myoclonic jerks, and intractable seizures. Cardiovascular: Hypotension (due to massive histamine release). Gastrointestinal: Constipation, nausea, biliary spasm (Sphincter of Oddi spasm).

Key Interactions

Benzodiazepines, Gabapentinoids (fatal respiratory arrest). Antihypertensives (Morphine's histamine release guarantees a massive BP drop if given fast IV to a patient on BP meds).

Monitoring

Monitor SpO2, RR, BP, and Sedation Score. If pushing IV, push slowly over 2-3 mins to minimize histamine/hypotension. Check eGFR before charting regular morphine.

Clinical Pearl

If an elderly patient with bad kidneys is given regular morphine, the M3G metabolite builds up in the brain. They will start violently twitching (myoclonus) and their pain will paradoxically get worse. Do not give them more morphine! Switch to Fentanyl/Hydromorphone and flush with fluids.

Access

Sevredol, Ordine (liquid)20 mg tablet

Brand: Sevredol, Ordine (liquid)
Formulation: Tablets IR (10, 20 mg). Oral liquid (2 mg/mL, 10 mg/mL).

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