Codeine phosphate is a type of medicine called an opioid. It's a painkiller, but also has cough suppressant and anti-diarrhoeal actions.

What is codeine phosphate used for?

  • Codeine phosphate is often just known as codeine. It's prescribed for:
  • Relieving mild to moderate pain in adults over 18 years of age.
  • Relieving dry, irritating, unproductive or painful coughs in adults and adolescents over 18 years of age.
  • Treating acute diarrhoea in adults and adolescents over 12 years of age.
  • Short-term relief of acute moderate pain in adolescents aged 12 to 18 years, when other painkillers such as paracetamol and ibuprofen have not been effective.

How does codeine phosphate work?

  • Codeine phosphate is a type of medicine called an opioid.
  • In treating pain, codeine works by mimicking the action of natural pain-reducing chemicals called endorphins that are produced in the brain and spinal cord.
Codeine acts on the same opioid receptors as natural endorphins and this blocks the transmission of pain signals sent by the nerves to the brain. This means that even though the cause of the pain may remain, less pain is actually felt.
  • In treating cough, codeine works by reducing the nerve signals sent from a part of the brain called the coughing centre to the muscles that produce coughing. Coughing is a reflex response to irritation of the airways and is usually helpful for clearing mucus, dust and other particles from the throat and lungs. However, sometimes, coughing can become overstimulated even when there is no mucus to clear from the lungs or throat. In this situation coughing serves no purpose and can become painful and frustrating. Codeine phosphate can be used to block the cough reflex in situations where the cough serves no purpose, ie when no phlegm is being coughed up.
  • In treating diarrhoea, codeine works by acting on opioid receptors that are found in the muscles lining the walls of the intestines. This slows done the muscular contractions of the intestine. It reduces the speed at which the gut contents are pushed through the intestines, allowing more time for water and electrolytes to be reabsorbed from the gut contents back into the body. This results in firmer stools that are passed less frequently and so controls diarrhoea.
  • How do I take codeine phosphate?

    • The codeine phosphate dosage prescribed, how often to take it and how long to take it for depends on the condition being treated, your age and your kidney and liver function. It's important to follow the instructions given by your doctor. These will also be printed on the dispensing label that your pharmacist has put on the packet of medicine.
    • Codeine phosphate tablets and liquids can be taken either with or without food.
    • If you forget to take a dose of codeine phosphate just leave out the missed dose. Do not take a double dose to make up for a missed dose.
    • Adolescents aged 12 to 18 years should not take codeine phsophate more often than every six hours, or for longer than three days.
    • If your symptoms persist despite taking codeine, get medical advice from your doctor or pharmacist.

    Important information about codeine phosphate

    • Codeine phosphate may cause drowsiness and dizziness.
    • It may be an offence to drive while you are taking codeine phosphate. Do not drive if you think it affects your ability to drive safely, for example if it makes you feel sleepy, dizzy, unable to concentrate or make decisions, or if you have blurred or double vision.
    • If you are driving dangerously while taking codeine you will be breaking the law. If you feel you are safe to drive while taking codeine, it's sensible to carry your prescription with you in case you are asked to take a saliva test by the police. If you test positive there is a medical defence if you are taking codeine as prescribed, as long as your driving is not impaired.
    • Do not drink alcohol while taking codeine phosphate, as it is likely to make any drowsiness or dizziness worse.
    • Do not exceed the prescribed dose of codeine, or take it more frequently or for longer than prescribed by your doctor. Taking codeine regularly for a long time can lead to addiction, which might cause you to feel restless and irritable when you stop taking the medicine.
    • If you find you need to use this medicine all the time you should consult your doctor for advice.
    • Taking a painkiller for headaches too often or for too long can actually make the headaches worse

    People can vary considerably in the way that their body metabolises codeine. For some people this may lead to an increased chance of getting side effects, such as reduced levels of consciousness; sleepiness; slow, shallow breathing; 'pin-point' pupils; lack of appetite; constipation; or nausea and vomiting. If you experience any of these you should stop taking this medicine and get medical advice straight away. For other people it may mean that the codeine is less effective, so if you find this medicine doesn't relieve your symptoms well enough you should consult your doctor.

    Who shouldn't take codeine phosphate?

    • Children under 12 years of age.
    • Adolescents aged 12 to 18 years who have had surgery to remove their tonsils or adenoids (tonsillectomy or adenoidectomy or both) for obstructive sleep apnoea.
    • People who are known to have a genetic variation of a liver enzyme called CYP2D6, which metabolises codeine into morphine (CYP2D6 ultra-rapid metabolisers). These people are more likely to experience side effects after taking codeine, because they convert more codeine into morphine than other people.
    • People with very slow, shallow breathing (respiratory depression).
    • People with chronic obstructive pulmonary disease (COPD).
    • People having an asthma attack.
    • People with liver failure.
    • People who have a blockage in their gut (paralytic ileus) or who are at risk of this.
    • People with a head injury or raised pressure inside the skull (intracranial pressure).
    • Women who are breastfeeding.
    • People who are allergic to any ingredient of the medicine.
    • Codeine is not recommended for treating diarrhoea or pain in adolescents aged 12 to 18 years who have problems with breathing, including those with neuromuscular disorders; severe heart or lung conditions; upper airway or lung infections; multiple trauma; or who have had extensive surgical procedures.
    • Codeine should not be used to treat a cough in adolescents under 18 years of age.

    Who might need a lower codeine dose or extra monitoring?

    • Elderly people.
    • People with kidney or liver problems.
    • People who suffer from breathing problems such as asthma.
    • People with a condition called bronchiectasis, in which there is persistent widening of the airways as a result of lung disease, eg infection, inflammation, tumours or cystic fibrosis.
    • People with gallstones or bile duct disorders.
    • People with acute abdominal conditions such as appendicitis.
    • People who have recently had surgery on the stomach, intestines, biliary tract or urinary tract.
    • People who are constipated.
    • People with bowel disorders such as Crohn's disease, ulcerative colitis or irritable bowel syndrome.
    • People who have difficulty passing urine, for example men with an enlarged prostate gland (prostatic hypertrophy).
    • People with an underactive thyroid gland (hypothyroidism).
    • People with underactive adrenal glands, eg Addison's disease.
    • People with low blood pressure (hypotension) or shock.
    • People with a condition involving abnormal muscle weakness called myasthenia gravis.
    • People with a history of convulsions or fits, eg epilepsy.
    • People with an irregular heartbeat (arrhythmia).
    • People with a history of drug or alcohol abuse or dependence.

    Can I take codeine while pregnant or breastfeeding?

    • The safety of codeine for use during pregnancy has not been established. If codeine is used regularly in the third trimester it may cause withdrawal symptoms in the baby after birth. If used during labour it may cause breathing difficulties in the baby after birth. It should be avoided during pregnancy and the late stages of labour, unless considered essential by your doctor, and then only if the expected benefit to the mother outweighs any potential risk to the baby. Seek further medical advice from your doctor.
    • Codeine passes into breast milk in amounts that are probably too small to be harmful in most people. However, because some people metabolise codeine in a slightly different way that can increase the risk of getting side effects from the medicine, it is recommended that women who are breastfeeding do not take codeine. It is impossible to predict which women and babies will metabolise codeine differently. Potential side effects in a nursing baby may include drowsiness or sedation, difficulty breastfeeding, vomiting, breathing difficulties and floppiness. You should not breastfeed while taking this medicine. If you do breastfeed, you should consult your doctor immediately or seek emergency medical care if your baby shows any of the symptoms just mentioned.

    What are the possible side effects of codeine phosphate?

    Medicines and their possible side effects can affect individual people in different ways. The following are some of the side effects that are known to be associated with codeine. Just because a side effect is stated here doesn't mean that all people taking codeine phosphate will experience that or any side effect.

    • Constipation.
    • Nausea and vomiting.
    • Dizziness or spinning sensation.
    • Drowsiness. See warnings above.
    • Confusion.
    • Headache.
    • Itching or nettle rash.
    • Slow, shallow breathing (respiratory depression).
    • Decreased blood pressure (hypotension).
    • Difficulty passing urine (urinary retention).
    • Dry mouth.
    • Sweating.
    • Flushing.
    • Mood changes.
    • Hallucinations.
    • Pin point pupils.
    • Blurred or double vision.
    • Changes in heart rate.
    • Decreased sex drive.
    • Convulsions.
    • Abdominal pain.
    • Loss of appetite.
    • Dependence on the medicine if used long periods of time.

    Read the leaflet that comes with the medicine or talk to your doctor, nurse or pharmacist if you want any more information about the possible side effects of codeine phosphate.

    Can I take codeine phosphate with other medicines?

    • It's important to tell your doctor or pharmacist if you're already taking any medicines, including those bought without a prescription and herbal medicines, before you start taking codeine phosphate. Similarly, check with your doctor or pharmacist before taking any new medicines alongside codeine, to make sure that the combination is safe.
    • You shouldn't take codeine phosphate if you've taken a type of medicine called a monoamine oxidase inhibitor (MAOI) in the last 14 days. MAOIs include the antidepressants phenelzine, tranylcypromine, isocarboxazid and moclobemide and the anti-Parkinson's medicine selegiline.

    You're more likely to feel drowsy if you take codeine phosphate with other medicines that cause drowsiness, such as the following:

    • antipsychotics, eg haloperidol, chlorpromazine
    • benzodiazepines, eg temazepam, diazepam
    • sedating antihistamines, eg chlorphenamine, promethazine, triprolidine, hydroxyzine (some of these may be found in non-prescription cough, cold and flu or hayfever remedies)
    • sleeping tablets, eg zopiclone
    • other strong opioid painkillers, eg dihydrocodeine, morphine, tramadol, co-codamol
    • tricyclic antidepressants, eg amitriptyline.

    You're more likely to get side effects like constipation, dry mouth and blurred vision if you take codeine with antimuscarinic medicines that can cause these type of side effects, such as the following:

    • antimuscarinic medicines for Parkinson's symptoms, eg procyclidine, orphenadrine, trihexiphenidyl
    • antimuscarinic medicines for urinary incontinence, eg oxybutynin, flavoxate, tolterodine, propiverine, trospium
    • antispasmodics, eg atropine, hyoscine.

    There is a risk of severe constipation if codeine is used with antimotility medicines for diarrhoea, such as loperamide.

    As codeine phosphate can reduce the muscular activity in the gut, it may oppose the effect of the following medicines:

    • domperidone
    • metoclopramide.
    • Codeine may be less effective if you're taking rifampicin or ritonavir.