Co-codamol: strengths, dependence risk and safe use

Co-codamol is a mixture of two painkillers. The NHS describes it as used for aches and pains such as period pain, muscle pain and toothache, and says it may help when everyday painkillers like ibuprofen, aspirin or paracetamol alone have not worked. It is available as tablets, capsules and soluble tablets that dissolve in water.

The two ingredients act differently. Paracetamol seems to work by blocking chemical messengers in the brain that signal pain and also lowers temperature. Codeine is an opioid that acts on pain receptors in the central nervous system and brain. The same action explains its unwanted effects: slower and shallower breathing, and slowed digestion, hence constipation.

Packets show two numbers, the codeine then the paracetamol. The three strengths are 8/500, 15/500 and 30/500. All hold the same paracetamol as a standard tablet, so the codeine is what makes them stronger. The NHS notes you are more likely to have side effects from the higher strengths.

For adults the NHS gives 1 or 2 tablets, of any strength, up to 4 times in 24 hours with a gap of at least 4 to 6 hours, and says the maximum is 8 tablets in 24 hours. It adds that you should not take more than 2 at once even if the pain is severe; if the dose is not enough, speak to a pharmacist or doctor rather than increasing it. The reason is the paracetamol: too much can cause liver damage.

With long use the body can become tolerant to codeine, so higher doses are needed to get the same effect. Some people become more sensitive to pain, called hyperalgesia; the NHS says the doctor then reduces the dose gradually. It is also possible to become addicted to the codeine, which is why doses are reviewed and why a treatment plan may set out how and when to stop.

Signs of dependence include finding it hard to stop or feeling a need to take it more often than intended. Stopping suddenly can bring withdrawal: agitation or anxiety, panic attacks, palpitations, difficulty sleeping, shaking, sweating, body aches and restlessness. If you have taken it for more than a few weeks, do not stop without speaking to your doctor.

The NHS lists constipation, feeling or being sick, and feeling sleepy or dizzy as the common effects, with headaches also possible. Constipation is best met with fibre, fluids and activity; if sickness continues beyond a few days, a doctor can discuss an anti-sickness medicine.

Rare serious effects include a skin rash, difficulty passing urine, changes in eyesight, muscle stiffness and symptoms of low blood pressure. Call 999 or go to A&E for breathing difficulty, short shallow breathing, or a fit. Swelling of the lips, mouth, throat or tongue is a possible anaphylaxis and also needs 999.

• Do not drive, cycle or use tools if you feel sleepy, dizzy or have blurred vision.

• Police can request a saliva sample to check drug levels even if driving seems unaffected.

Tell your doctor before starting if you have lung or breathing problems, a head injury, adrenal gland problems, a condition causing fits, liver problems (a lower dose may be needed), or if you regularly drink more than 14 units of alcohol a week. People under 18 who have had tonsils or adenoids removed for sleep apnoea should not take it. Most adults can take it, and most young people aged 12 to 17 can, but only if other painkillers have not worked.

Pregnancy: it can be taken, though long-term use is not recommended. Paracetamol is safe, but codeine near the end of pregnancy can leave a baby drowsy or with withdrawal after birth. Breastfeeding: do not take it, as small amounts of codeine reach the milk and could cause breathing problems in a baby; paracetamol is the better choice. Short use at normal doses is unlikely to affect fertility.

Tell your doctor if you take sleeping pills or tranquillisers (particularly benzodiazepines such as diazepam, temazepam or lorazepam), some antidepressants, anti-sickness drugs such as domperidone or metoclopramide, anticoagulants such as warfarin, the antibiotics rifampicin or ciprofloxacin, or epilepsy medicines. It is safe with ibuprofen and aspirin.

Do not take it with other paracetamol-containing products unless a doctor says so; the NHS names Tramacet, co-dydramol, some migraine remedies and cold and flu remedies such as Lemsip and Night Nurse. Alcohol makes drowsiness worse and raises the risk of serious side effects, so avoid it in the first days. Recreational drugs such as cannabis, cocaine and especially heroin make serious effects more likely.