Codeine for pain relief is a prescription opioid medicine used for acute moderate pain when painkillers such as paracetamol or ibuprofen alone have not provided enough relief. It can be effective for some people, but it can also cause sleepiness, constipation, nausea, breathing problems, dependence and addiction, so it should be used only as directed by a prescriber.
This guide focuses specifically on codeine as a pain medicine in the UK. It explains when it may be used, how it works, common side effects, important safety risks and when medical help is needed. It is general information and does not replace advice from your doctor, prescriber or pharmacist.
Codeine Phosphate is an opioid painkiller. The NHS describes it as a medicine used for pain, including pain after an operation or injury, and notes that it is often used when other painkillers such as paracetamol or ibuprofen have not worked well enough.
Codeine itself is available on prescription in the UK. Lower-strength codeine can also appear in combination medicines with other painkillers, such as paracetamol or ibuprofen, but those are different products with their own instructions and risks.
Codeine works through the opioid system in the brain and central nervous system. A key part of its pain-relieving effect comes from the body converting some codeine into morphine through a liver enzyme called CYP2D6. Morphine then acts on opioid receptors involved in how pain signals are processed.
People do not all process codeine in the same way. Some people convert less codeine to morphine and may get less pain relief, while others can convert it more quickly and may have a higher risk of opioid side effects. This variation is one reason codeine should be used according to professional advice rather than by increasing the dose yourself.
Codeine may be considered for acute moderate pain when simpler painkillers have not provided adequate relief. Official UK product information lists acute moderate pain that is not considered to be relieved by analgesics such as paracetamol or ibuprofen alone as an indication for codeine.
The exact reason for prescribing codeine depends on the cause of the pain, the person’s medical history, other medicines being taken and the expected duration of treatment. A prescriber should decide whether an opioid is appropriate rather than codeine being treated as a general first-choice painkiller.
Take codeine exactly as directed on your prescription and medicine leaflet. The dose and duration can vary depending on why it has been prescribed. Official product information advises using the lowest effective dose for the shortest appropriate period and reviewing treatment if pain relief is not adequate.
Common side effects include constipation, nausea or vomiting, sleepiness or tiredness, and sweating. Not everyone gets side effects, and their severity can vary from person to person.
If codeine makes you sleepy or tired, do not drive, ride a bike or use machinery until those effects have passed. If side effects are troublesome, persistent or getting worse, speak to a pharmacist or doctor rather than changing the dose yourself.
The most important serious risk is excessive opioid effect, particularly slow, weak or shallow breathing. Other serious reactions can include a severe allergic reaction, marked dizziness or weakness from low blood pressure, or an unusual heartbeat. Serious effects are not expected in most people, but they need prompt medical assessment when they occur.
Taking too much codeine can cause a dangerous opioid overdose. Warning signs can include extreme drowsiness, confusion, very small pupils, slow or difficult breathing, blue or purple lips or fingernails, or loss of consciousness.
Yes. Repeated or prolonged use of codeine can lead to physical dependence, tolerance and, in some people, addiction. Dependence and addiction are related but not identical. Physical dependence means the body has adapted to the medicine and withdrawal symptoms may occur if it is stopped suddenly; addiction involves loss of control over use and continued use despite harm.
Possible warning signs include craving the medicine, feeling a need to take more than directed, using it for reasons other than pain relief, or experiencing withdrawal symptoms when stopping. If codeine seems less effective, do not increase the dose yourself. Speak to the prescriber because tolerance, the underlying pain condition or other factors may need review.
Codeine is not suitable for everyone. Before taking it, tell your prescriber about medical conditions and all medicines you use. Extra caution may be needed if you have breathing problems, liver or kidney disease, low blood pressure, a head injury, thyroid or adrenal problems, prostate problems, or a current or past history of alcohol, prescription-medicine or recreational-drug addiction.
Codeine should not be used in children under 12 because of the risk of opioid toxicity. There are also additional restrictions for some adolescents. If you are pregnant, trying to become pregnant or breastfeeding, tell your doctor; the NHS says codeine is not usually used while breastfeeding because it can cause side effects in the baby.
It is best not to drink alcohol while taking codeine because alcohol can increase opioid side effects such as sedation and can worsen breathing depression. Some other medicines can also increase drowsiness or breathing risk, including certain sedating medicines and other opioids.
Tell your doctor or pharmacist about prescription medicines, over-the-counter medicines, herbal products and supplements before starting codeine. In particular, do not combine codeine with another opioid-containing medicine simply because pain is still present without first getting professional advice.
No. Codeine is an opioid medicine, while co-codamol is a combination of codeine and paracetamol. Because co-codamol already contains codeine, taking additional codeine alongside it without medical advice can increase opioid exposure and risk.
For a focused comparison, read Co-Codamol vs Codeine: Which Is Right for Your Pain? rather than using this article as a dosing or substitution guide.
Contact NHS 111 if you have taken more than your prescribed dose of codeine, even if you are not sure whether symptoms will develop. Call 999 or go to A&E for severe symptoms such as serious breathing difficulty, collapse, loss of consciousness or another life-threatening reaction.
For non-emergency concerns, speak to your pharmacist, prescriber or GP if your pain is not adequately controlled, side effects are persistent, you are worried about dependence, or you want to stop codeine after regular longer-term use.
Yes. Codeine is an opioid painkiller. Its analgesic effect is partly produced after codeine is converted to morphine in the body.
No. The NHS states that codeine itself is prescription-only. Some lower-strength combination medicines containing codeine and another painkiller may be supplied through a pharmacy under different rules.
It can. Sleepiness or tiredness is a common side effect. Do not drive or use machinery if codeine is making you sleepy or affecting your concentration.
Do not increase the dose yourself. Speak to the prescriber or pharmacist so the cause of the pain, the treatment plan and safer alternatives can be reviewed.
For more patient-focused medicine information, visit the Medicine Guides section.
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