A strong opioid painkiller
Morphine
A strong opioid for severe pain, available as fast-acting and slow-release forms — a controlled drug with real risks of dependence and dangerous breathing problems.
What is Morphine?
Morphine is a strong opioid painkiller used for severe pain, for example after major surgery or injury, in cancer, and in palliative care. It is one of the most established medicines for serious pain but needs careful, supervised use.
Education and reference only. This is a plain-language guide to Morphine — it deliberately contains no doses. Doses depend on the person, the brand and the reason for treatment, and belong with your prescriber. Always check the BNF, the product labelling (SmPC) and follow medical advice.
What it is
Morphine is a strong opioid painkiller used for severe pain — for example after major surgery or injury, in cancer, and in palliative care. It is one of the most effective treatments for serious pain but, because of its risks, it is a controlled drug and is used carefully and for clear reasons. It comes in two broad types: immediate-release forms that act quickly for a few hours (such as Oramorph liquid and Sevredol tablets) and modified-release forms that release slowly for steady, longer cover (such as MST Continus and Zomorph). It works on the same system as the body's natural painkillers.
How it works
Morphine attaches to opioid receptors in the brain, spinal cord and elsewhere — the same receptors the body's own natural painkillers use. By switching these on, it changes how pain signals are processed and how the brain perceives pain, dialling down both the intensity and the distress of severe pain. The same receptors influence breathing, the bowel and the reward pathways, which is why morphine can also slow breathing, cause constipation, and, with repeated use, lead to tolerance and dependence.
Company & origin
Originated / developed by: Merck.
Morphine was first isolated from opium around 1804 by the German pharmacist Friedrich Wilhelm Sertürner, and was later commercialised on an industrial scale by the German firm Merck from the 1820s onward.
Practical use
How to take Morphine
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- Take morphine exactly as prescribed and never more often than directed, as opioids carry a real risk of dependence and overdose.
- Expect drowsiness, especially at first; do not drive or use machinery until you know how it affects you.
- Strong opioids can impair driving and there are specific UK rules on driving while taking them — check with your prescriber before you drive.
- Do not drink alcohol or take sedatives, sleeping tablets or other opioids alongside it, as the combination can dangerously slow your breathing.
- Constipation is very common, so ask your team about a laxative and keep up your fluids and fibre.
- Do not stop morphine suddenly after regular use, as this can cause withdrawal symptoms; any reduction should be planned with your prescriber.
- Report severe drowsiness, confusion or slow, shallow breathing urgently.
Weighing it up
Advantages & disadvantages of Morphine
Advantages
- Very effective for severe and palliative pain when milder painkillers are not enough.
- Available in different forms, allowing flexible pain control.
- Long-established medicine with well-understood effects.
- Central to good end-of-life and cancer pain care.
Disadvantages
- Carries a genuine risk of tolerance, dependence and addiction with longer-term use.
- Commonly causes constipation, drowsiness, nausea and itching.
- Dangerous if combined with alcohol or other sedating medicines because of breathing risk.
- Must not be stopped abruptly after regular use, to avoid withdrawal.
Practical use
Good to know
Morphine is highly effective but must be respected. Constipation is almost universal and is usually managed with a laxative from the start; drowsiness and feeling sick are common early on and often settle. The most dangerous risk is slowed breathing (respiratory depression), which can be fatal — this danger rises sharply if morphine is combined with alcohol, sleeping tablets, or other sedatives. With ongoing use the body develops tolerance and physical dependence, so it should not be stopped suddenly but reduced gradually. Immediate-release forms are for quick or breakthrough pain, while modified-release forms give steady background cover — mixing them up can be dangerous. The effect is stronger and longer in people with reduced kidney function.
Who should not take it / use with caution
- People with significant breathing problems or respiratory depression, or a severe acute asthma attack.
- Used with great caution in reduced kidney or liver function, head injury, very low blood pressure, or a blocked or paralysed bowel.
- Care in older or frail people, in those who also take sedatives or alcohol, and in pregnancy and breastfeeding — used only when clearly needed and monitored.
Monitoring
- Pain control and how it affects daily function
- Drowsiness, breathing and signs of overdose
- Bowel function (constipation) and ongoing need for the opioid
Side effects
- Constipation (very common — usually needs a laxative), nausea and vomiting, and drowsiness.
- Dry mouth, itching, sweating, confusion, or low blood pressure and dizziness.
- Most seriously, slowed or shallow breathing (respiratory depression), which can be life-threatening — especially with sedatives or alcohol, in overdose, or where kidney function is reduced.
Key interactions
- Alcohol, sleeping tablets, benzodiazepines, gabapentin/pregabalin and other sedating medicines greatly increase the risk of dangerous breathing problems and excessive drowsiness.
- Other opioids and some medicines for nausea or mental health can add to its sedating effects.
- Tell every prescriber and pharmacist that you take morphine, and avoid alcohol while on it.
Available as: Immediate-release tablets and liquid (such as Sevredol and Oramorph) for fast or breakthrough pain, modified-release tablets and capsules (such as MST Continus and Zomorph) for steady cover, and injectable forms used in hospital and palliative care.
Answers
Morphine: frequently asked questions
What is the difference between immediate-release and modified-release morphine?
Immediate-release forms (such as Oramorph liquid and Sevredol tablets) act quickly and last a few hours, useful for sudden or breakthrough pain. Modified-release forms (such as MST Continus and Zomorph) release morphine slowly for steady, longer background cover. They are used for different purposes, and confusing the two can be dangerous — always follow exactly which form is which.
Will I become addicted to morphine?
Used as prescribed for genuine severe pain, the helpful pain relief is the main effect, but the body does develop tolerance and physical dependence over time. That is why morphine is reviewed regularly and reduced gradually rather than stopped suddenly. Tell your team about any concerns or a history of dependence so it can be managed carefully.
Why is mixing morphine with alcohol or sleeping tablets dangerous?
Morphine can slow your breathing, and alcohol, sleeping tablets and other sedatives do the same. Combined, they can dangerously — even fatally — depress breathing. Avoid alcohol while taking morphine, and tell your prescriber about any sedating medicines you take.
Why have I been given a laxative with it?
Constipation from morphine is almost universal and, unlike drowsiness, does not wear off with time. A laxative is usually started alongside the morphine to prevent it. Drink plenty of fluids and tell your team if constipation is still a problem.
What is the difference between morphine and its brand names?
They are the same active ingredient — morphine is the generic name, and Oramorph, Sevredol, MST Continus and Zomorph are brands of its different (immediate- or modified-release) forms. The active ingredient is identical; the forms differ in how quickly and for how long they release it.
The wider class
About Opioid analgesics
Morphine belongs to the opioid analgesics class. For how the class as a whole works, its shared safety principles and monitoring, see the full guide.
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Authoritative sources
- BNF: Morphine.
- electronic Medicines Compendium (SmPC): Morphine (Oramorph, MST Continus, Zomorph, Sevredol).
- NICE CKS: Morphine.
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