Morphine: clinical use

Prescribing considerations

• Agree treatment goals, review ongoing benefit and harm, and establish a discontinuation plan before prolonged treatment.
• Assess current medicines, respiratory disease, gastrointestinal motility, hepatic and renal function, mental health, and personal or family history of substance use disorder.
• Consider tolerance, opioid-induced hyperalgesia or disease progression when pain control deteriorates.
• Account for route and formulation when switching. Prolonged-release brands may not be bioequivalent.
• Use additional caution in older or frail people and those at increased risk from sedation or respiratory depression.

Contraindications and cautions

• Hypersensitivity to morphine or relevant excipients.
• Severe respiratory depression, severe asthma or severe obstructive pulmonary disease, as specified by the product.
• Paralytic ileus, acute abdomen or delayed gastric emptying.
• Acute hepatic disease.
• Concurrent or recent monoamine oxidase inhibitor treatment.
• Some products additionally contraindicate acute head injury, raised intracranial pressure, uncontrolled seizures or particular paediatric age groups; verify the selected product information.

Monitoring

• Pain relief, function and continued clinical need.
• Sedation, respiratory status and signs of sleep-related breathing disorder.
• Constipation, nausea, urinary retention and biliary symptoms.
• Renal and hepatic function where impairment is present or develops.
• Tolerance, withdrawal, early refill requests, non-prescribed opioid use and other signs of opioid use disorder.
• Possible endocrine or adrenal effects during long-term treatment.
• New diffuse or poorly defined pain suggesting opioid-induced hyperalgesia.

Clinical pharmacology

Morphine is principally a mu-opioid receptor agonist, with lesser activity at kappa receptors. It undergoes hepatic glucuronidation. Metabolites, including active morphine-6-glucuronide, are predominantly cleared renally and may accumulate in renal impairment.

Formulation and product differences

• Immediate-release oral solution and orodispersible tablets are distinct from prolonged-release products and must not be substituted without considering release characteristics.
• MST Continus and Morphgesic SR are prolonged-release tablets that must be swallowed whole.
• MXL is a prolonged-release capsule that may be opened for sprinkling onto soft, cold food, but its granules must remain intact.
• Actimorph is an orodispersible tablet that disperses in the mouth or in a small amount of water on a spoon.
• The selected injection is intended for intravenous patient-controlled analgesia in appropriately staffed and equipped clinical settings.
• Excipients differ between products, including sugars, alcohol, lactose, colourings, sulphites and benzyl alcohol; check the product-specific information.

Dispersible tablet

Route: Oral

Strengths: 1 mg, 2.5 mg, 5 mg, 10 mg, 20 mg, 30 mg