Medically reviewed by Dr Fatimah Khan, registered with the Pakistan Medical and Dental Council (PMDC no. 104595-P). Editorial medical reviewer; does not prescribe or review patient assessments.
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What is codeine used for?
Codeine is an opioid used in some pain medicines, either alone or combined with another ingredient. The NHS codeine guide explains its use for pain when ordinary painkillers have not been sufficient.
Calling it a “weak opioid” describes a drug category, not an assurance that it is harmless. Codeine can cause dependence, sedation and serious breathing problems.
Why metabolism changes the response
The body converts some codeine into morphine. Conversion differs between people: some obtain little benefit, while ultrarapid metabolisers can develop dangerously high morphine exposure.
The EMA's 2013 review of codeine for pain relief explains the resulting restrictions, including known ultrarapid metabolisers and breastfeeding. Children's use involves additional restrictions and must not be inferred from adult guidance.
Do not compensate for poor pain relief by taking more than directed. A clinician should review the diagnosis and the treatment rather than assume that a larger amount is appropriate.
Codeine alone versus combination products
| Product type | What to check |
|---|---|
| Codeine alone | The exact strength, indication and prescribed course |
| Codeine with paracetamol, such as co-codamol | Both ingredient amounts and other paracetamol-containing medicines |
| Another codeine combination | Every active ingredient and the product-specific warnings |
Different presentations can have different indications and local controls. Information about pain medicine does not establish the right use of a cough product.
Side effects and warning signs
Constipation, nausea, dizziness and sleepiness can occur. Do not drive or operate machinery if affected. Alcohol, other opioids and sedating medicines can increase risk; a pharmacist or prescriber should check combinations.
Slow or shallow breathing, severe difficulty breathing or an inability to wake someone needs emergency help. Taking more than directed requires urgent advice. Regular use can lead to dependence, so continuing need and an eventual stopping plan should be reviewed.
This article does not give a standalone dose or a universal duration. Follow the instructions for the actual medicine and the prescriber's plan.
What can be said about access in Europe?
The EMA describes nationally authorised codeine products with different prescription and non-prescription arrangements. Check the actual product's current status with a pharmacist or the relevant national regulator; access cannot be inferred from another country's rules.
For checking a service, see medicine-access rules and warning signs. Prescrivia is a technology intermediary. Independent clinicians decide suitability, and licensed pharmacies dispense where appropriate. No opioid prescription, access or result is guaranteed.
General information only, not medical advice. Follow the leaflet for your actual product and discuss decisions with a qualified clinician. See the current clinical, legal and language review statuses for this edition.
Sources
- NHS UK guidance: pain indications, individual course selection, sedation, dependence, interactions and emergency breathing advice.
- EMA 2013 codeine review: metabolism to morphine, ultrarapid-metaboliser and breastfeeding restrictions, paediatric pain limits and nationally variable access.
Sources checked online on 6 October 2026. Country-specific guidance does not establish availability or prescribing rules throughout Europe.