Co-dydramol: paracetamol with dihydrocodeine

The NHS describes co-dydramol as a mixture of paracetamol and dihydrocodeine, an opiate. It is used for aches and pains including headaches, migraines, muscle and joint pain, period pain and toothache, and is usually taken when everyday painkillers such as aspirin, ibuprofen and paracetamol have not worked alone. It generally comes as tablets.

Both ingredients block pain messages in the nerves and brain. Dihydrocodeine can also slow breathing and digestion, which accounts for the breathing warnings and the constipation.

Each tablet has the same 500mg of paracetamol as a standard paracetamol tablet; what changes is the dihydrocodeine. The packet shows the dihydrocodeine first, so 10/500 contains 10mg of dihydrocodeine and 500mg of paracetamol. The lowest strength, 7.46/500, can be bought from a pharmacy, while the other three are only available on prescription.

Do not take more than the maximum, which for adults and over-16s is 8 tablets in 24 hours. For ages 12 to 15, the daily limit depends on strength, source and age, so the NHS says to ask a doctor or pharmacist. Tablets are swallowed whole with water, without crushing, though scored tablets may be halved if swallowing is difficult.

From a pharmacy, do not use it for more than 3 days without talking to a doctor. If prescribed, take it for as long as the prescriber advises, which may be a few days or weeks after an injury or operation. If you have taken a prescribed course for more than a few weeks, speak to your doctor before stopping.

Prolonged use can lead to tolerance, hyperalgesia (greater sensitivity to pain, handled by gradually reducing the dose) and addiction. Signs of dependence include difficulty stopping or needing more than necessary. Stopping suddenly may cause agitation, anxiety, panic attacks, palpitations, sleeplessness, shaking, sweating, body aches and restlessness.

Common effects, in more than 1 in 100 people, are constipation, feeling or being sick, sleepiness, headache and dizziness. Higher strengths make side effects more likely. Sleepiness often settles within a few days; speak to your doctor if it continues.

Rare serious effects are a skin rash, difficulty peeing and changes in eyesight; tell a doctor or call 111. Anaphylaxis needs 999. Overdose is dangerous partly because the paracetamol can damage the liver: if you take more than 2 extra tablets, more than 8 in 24 hours, or are struggling to breathe, seek urgent help.

You can take it in pregnancy if you need to. Paracetamol is safe, but dihydrocodeine towards the end of pregnancy may cause withdrawal such as drowsiness in the baby after birth, which may mean extra hospital observation. Discuss options with your doctor.

While breastfeeding it is usually fine if your doctor or midwife says your baby is healthy, but take it only on advice, in low doses and for a short time. Paracetamol alone is usually better. Long use of higher-strength co-dydramol can cause hypogonadism, making it harder to conceive or to father a child, but hormones should recover when it stops.

Tell your doctor if you have had an allergic reaction to it, have digestion problems such as irritable bowel syndrome or Crohn disease, lung problems or asthma, a head injury, adrenal insufficiency, seizures, an underactive thyroid, liver or kidney problems, myasthenia gravis, or regularly drink more than 14 units a week. Do not give it to a child under 12 unless prescribed.

Check before starting if you take sleeping pills or tranquillisers, antidepressants, domperidone or metoclopramide, warfarin, antihistamines, epilepsy medicines, antipsychotics, tuberculosis medicines or anxiety medicines. Alcohol can make you sleepier and raise serious side-effect risk, so avoid it in the early days. Cannabis, cocaine and heroin make serious effects more likely. Avoid driving if drowsy or dizzy.