Written by Chloe Doris
Last Reviewed: September 2019
Review Due: September 2020
mechanism of action2
Morphine belongs to a group of drugs known as opioids – they exert their effect through direct G-protein coupling to the ion channels on neuronal membranes in the CNS and GI tract.
They promote the opening of potassium channels and inhibit the opening of voltage-gated calcium channels. These membrane effects decrease neuronal excitability and reduce neurotransmitter release – the overall effect is therefore inhibitory.
Pain (acute and chronic)
Acute pulmonary oedema
Palliative care (cough, pain, dyspnoea at rest)
Dependence or withdrawal
Constipation, GI discomfort, reduced appetite
Dizziness, drowsiness, dry mouth
Acute respiratory depression
Raised intracranial pressure
Should be cautious. Avoid oral administration in acute impairment.
Avoid use or reduce dose. Opioid effects increased and prolonged.
Alcohol causes rapid release of morphine.
Buprenorphine and pentazocine are predicted to increase the risk of opiate withdrawal when given with morphine.
Many drugs can have CNS depressant effects which might affect ability to perform skilled tasks.
Drowsiness may affect performance of skilled tasks and the effects of alcohol will be enhanced. Driving should be avoided at the start of therapy and following any dose changes.
Repeated use of Morphine is associated with the development of psychological and physical dependence – caution is prescribing to patients with a history of drug abuse.
British National Formulary. Morphine. (2019)
Rang H.P, Ritter J.M, Flower R.J, Henderson G. Rang & Dale’s Pharmacology. 8th Ed. Elsevier Churchill Livingstone; 2016. Page 519.
British National Formulary. Interactions: Morphine. (2019)