Quick answer
What is codeine used for?
Codeine is an opioid converted in the body to morphine, used short-term for moderate pain. Effect varies between people. Constipation and drowsiness are common. It is not for children under 12, and is usually avoided when breastfeeding. Overdose can slow breathing — call 999 if this is suspected.
How codeine works
Codeine is a prodrug. The liver enzyme CYP2D6 converts it into morphine, which relieves pain. Because this enzyme varies between people, the same dose can feel weak for one person and strong for another.
It is generally a second-line option when paracetamol or ibuprofen alone have not been enough.
What codeine is used for
Codeine is used short-term for moderate acute pain — for example after injury or dental work — sometimes in combination products. It is occasionally used for diarrhoea under medical advice.
It is not a good long-term solution for chronic pain. Ongoing pain needs a proper review of causes and other treatments such as physiotherapy, non-opioid medicines, or specialist input.
Side effects
Common effects include constipation, nausea, dry mouth and drowsiness. Drinking plenty of fluid, staying mobile, and asking about a laxative can help if constipation develops.
Tolerance (needing more for the same effect) and dependence can appear with continued use. Keep courses as short as possible.
Who should avoid codeine
Codeine should not be used in children under 12, and is restricted in many under-18s, especially after tonsil or adenoid surgery. It is usually avoided when breastfeeding because morphine can pass into breast milk in unpredictable amounts.
People with severe breathing problems, acute asthma attacks, or who take other sedating medicines need particular caution. Store codeine securely away from others.
Overdose and getting help
Too much codeine — alone or with alcohol or other sedatives — can cause life-threatening breathing depression. Call 999 if breathing is slow, the person is hard to wake, or lips look blue.
If you are worried about how much codeine you are using, talk to a GP or pharmacist early. Help is available, and asking is a sign of looking after yourself.
Common questions about codeine
- Why does codeine not work for some people?
- Some people are genetic "poor metabolisers" and convert little codeine into morphine, so pain relief is weak. Others are ultra-rapid metabolisers and may get stronger effects and more side effects. If codeine fails, a GP can suggest a different painkiller.
- Can I take codeine with other opioids or sleep medicines?
- Combining opioids, or taking codeine with benzodiazepines or alcohol, increases the risk of dangerous sedation and breathing problems. Always tell a GP or pharmacist about every medicine and supplement you use.
- What withdrawal symptoms can codeine cause?
- After regular use for more than a short period, stopping suddenly can cause restlessness, runny nose, tummy cramps, sweating and poor sleep. A GP can help you taper safely rather than stopping abruptly.
- Is codeine still used for cough?
- Codeine linctus for cough is tightly restricted in the UK because of limited benefit and misuse risk. Do not use leftover painkiller codeine for cough. Ask a pharmacist about safer cough care.
- Can I drive on codeine?
- Codeine can impair driving. It is illegal to drive if you are unfit because of drugs, including medicines. Do not drive until you know how it affects you, and never drive if you feel drowsy.