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Side Effects


Codeine phosphate should be used with caution in:

It should not be used in: children under 12 years of age, patients who are allergic to codeine or other opioids or any of the other ingredients in the medicine, patients who have severe breathing problems, patients who have suffered a head injury or raised pressure in the skull (symptoms of painful eyes changes in sight or headache behind the eyes), patients who are having an asthma attack, liver disease, alcoholism, conditions with symptoms of severe acute diarrhoea (acute ulcerative colitis, antibiotic-associated colitis), patients who may have a blocked intestine, swollen abdomen.

Also see list of precautions and interactions


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  • Codeine phosphate is used to relieve mild to moderate pain, coughing and diarrhoea.
  • It is an opioidanalgesic, sometimes known as a painkiller.
  • It is used to relieve pain by mimicking the action of endorphins which are pain-reducing chemicals that occur naturally in the body. Codeine phosphate also relieves coughing by suppressing the cough reflex which reduces the nerve signals that travel from the coughing centre in the brain to the muscles that produce the coughing. By acting on opioid receptors in muscles lining the walls of the intestine, codeine phosphate also enables the body to produce firmer stools that are passed less often, relieving the symptoms of diarrhoea.
  • In general this drug is used treat mild to moderate pain, diarrhoea and cough.
  • Benefits of being on this drug can include relief from pain, relief from the symptoms of diarrhoea with firmer less frequent stools, and a reduction in coughing.

Listed below are the typical uses of codeine phosphate.

  • Mild to moderate pain
  • Diarrhoea
  • Dry or painful cough

On occasion your doctor may prescribe this medicine to treat a condition not on the above list.


How often do I take it?

  • Take this medication orally usually three to four times a day, with or without food. For pain relief, codeine phosphate may be taken every 4 hours. Swallow the tablets whole with water. It is important that you do not take more than the maximum amount of codeine phosphate that you have been recommended to take each day. If you have any questions about this consult with your doctor or pharmacist. Some patients may be prescribed codeine phosphate injection instead of an oral (by mouth) preparation. Codeine phosphate injection is injected into a muscle usually every 4 hours by a doctor or nurse.
  • Use this medication regularly in order to get the most benefit from it.
  • Remember to use it at the same time each day - unless specifically told otherwise by your doctor.
  • It may take up to 4 hours before the full benefit of this drug takes effect.
  • Certain medical conditions may require different dosage instructions as directed by your doctor.

What dose?

  • Dosage is based on your age, gender, medical condition, response to therapy, and use of certain interacting medicines.

Do I need to avoid anything?

  • Codeine phosphate may cause drowsiness, confusion, dizziness, fitting, blurred or double vision or make you see things that are not there. If you have any of these symptoms do not drive or operate machinery. Consult your doctor or pharmacist for more details.

When can I stop?

  • Always complete the full course as prescribed by your doctor.


  • Pains in the abdomen
  • Feeling or being sick
  • Dry mouth
  • Weight loss (anorexia)
  • Fitting (seizures)
  • Tiredness
  • Drowsiness
  • Dizziness and spinning sensation
  • Reduction in body temperature (hypothermia)
  • Muscle stiffness
  • Inflammation of the pancreas (pancreatitis)
  • Constipation
  • Reduction in breathing rate (respiratory depression) or difficulty breathing
  • Slow or fast heart rate
  • Low blood pressure including when standing up
  • Pain and difficulty when passing water (urine)
  • Needing to pass water (urine) less frequently
  • Mood changes
  • Depression
  • Decrease in sex drive
  • Seeing or hearing things that are not real (hallucinations)
  • Restlessness
  • Feeling very excited
  • Nightmares
  • Confusion
  • Blurred or double vision
  • Very small pupils
  • Painful eyes, changes in eyesight and headache behind the eyes (caused by increased pressure in the skull)
  • Withdrawal symptoms if the medicine is stopped too quickly (tremor, sweating, increased heart rate and breathing rate, increase in blood
  • pressure and feeling sick)
If any of these persist or you consider them severe then inform your doctor or pharmacist.

Tell your doctor immediately if you develop any of the following symptoms:

  • Skin rash or itchy skin, difficulty breathing, increased sweating, redness or flushed face.

Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

A serious allergic reaction to this drug is unlikely, but seek immediate medical attention if it occurs. Symptoms of a serious allergic reaction include: rash, itching/swelling (especially of the face/tongue/throat), dizziness, trouble breathing.

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

The Yellow Card Scheme allows you to report suspected side effects from any type of medicine (which includes vaccines, herbals and over the counter medicines) that you are taking. It is run by the medicines safety watchdog called the Medicines and Healthcare products Regulatory agency (MHRA). Please report any suspected side effect on the Yellow Card Scheme website.


Before taking codeine phosphate, tell your doctor or pharmacist if you are allergic to it; or to other opioids; or if you have any other allergies.

This medication should not be used if you have certain medical conditions. Before using this medicine, consult your doctor or pharmacist if you have: an allergy to codeine or other opioids or to any of the other ingredients in the medicine, severe breathing problems, suffered a head injury or raised pressure in the skull with symptoms of painful eyes changes in sight or headache behind the eyes, an asthma attack, liver disease, alcoholism, conditions with symptoms of severe acute diarrhoea (acute ulcerative colitis, antibiotic-associated colitis), a blocked intestine, swollen abdomen.

Before using this medication, tell your doctor or pharmacist your medical history, especially any of the following abnormal heart rhythm (cardiac arrhythmias), gallstones or gall bladder disease, asthma, kidney disease, liver problems (but not actual liver disease), asthma or breathing problems, history of drug abuse or alcoholism, disease of the adrenal gland (Addison's disease), high blood pressure caused by a tumour near the kidney (phaeochromocytoma), inflammation of the bowel (inflammatory bowel disease), have recently had surgery on their urinary system (including the kidney, bladders, ureter, urethra and penis) or gastrointestinal tract (including stomach and intestines), an enlarged prostate gland and difficulty passing water (urine), epilepsy (seizures), underactive thyroid (hypothyroidism), muscle weakness (myasthenia gravis), low blood pressure or are in shock, history of mental illness, an intolerance to certain sugars.

Before having surgery, tell your doctor or dentist that you are taking this medication.

Does alcohol intake affect this drug?

  • Avoid alcohol whilst taking codeine phosphate.

The elderly: codeine phosphate should be used with caution in the elderly at a lower dose, particularly in those with liver or kidney problems.

Pregnancy and breastfeeding - please ensure you read the detailed information below


Codeine phosphate is not safe to take if you are, or are planning to become, pregnant.

It is sensible to limit use of medication during pregnancy whenever possible. However, your doctor may decide that the benefits outweigh the risks in individual circumstances and after a careful assessment of your specific health situation.

If you have any doubts or concerns you are advised to discuss the medicine with your doctor or pharmacist



Codeine phosphate is not safe to take if you are breastfeeding

It is sensible to limit use of medication during breastfeeding whenever possible. However, your doctor may decide that the benefits outweigh the risks in individual circumstances and after a careful assessment of your specific health situation.

If you have any doubts or concerns you are advised to discuss the medicine with your doctor or pharmacist.


Before using this medicine, tell your prescriber of all the medicines you are taking including prescription medicines and medicines you have bought over the counter without a prescription. Tell your prescriber if you are taking vitamins or complementary remedies such as herbal products, as these can also interact with medicines.

If you are taking more than one medicine, these may interact with each other. Your prescriber may decide to use medicines which interact with each other if the benefit outweighs the risks. In these cases, the dose of your medicines may need to be adjusted or you may be monitored more closely.

The following medicines may interact with codeine phosphate:

  • Monoamine oxidase inhibitor drugs (MAOIs) such as moclobemide, linezolid, selegiline. Codeine phosphate tablets should not be taken for 2 weeks after stopping MAOIs
  • Alcohol
  • Tricyclic antidepressants, such as amitriptyline
  • Ciprofloxacin
  • Mexiletine
  • Quinidine
  • Metoclopramide
  • Domperidone
  • Loperamide
  • Kaolin
  • Cimetidine
  • Medicines for high blood pressure
  • Antihistamine medicines that may cause drowsiness
  • Atropine
  • Chlorpromazine
  • Haloperidol
  • Diazepam
  • Nitrazepam
  • Temazepam
  • Anaesthetics
  • Opioid antagonists such as buprenorphine, naltrexone, naloxone
  • Medicines for viral infections (such as ritonavir)

This information does not contain all possible interactions. Therefore, tell your prescriber of all the products you are using before taking this medicine.

If you have a question or want to discuss anything about your medicine, speak to your local pharmacist.


Symptoms of an overdose include feeling or being sick, feeling drowsy and tired, low blood pressure, very small pupils (pinpoint pupils), slow breathing rate and fast heart rate. If you or someone else take too much codeine phosphate or a you think a child may have taken codeine phosphate contact your nearest hospital casualty department or tell your doctor immediately.

If you think you, or someone you care for, might have accidentally taken more than the recommended dose of codeine phosphate or intentional overdose is suspected, contact your local hospital, GP or if in England call 111. In Scotland call NHS 24. In Wales, call NHS Direct Wales. In the case of medical emergencies, always dial 999.


If you miss a dose, take it as soon as you remember. If it is near the time of the next dose, skip the missed dose and resume your usual dosing schedule. Do not double the dose to catch up.

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Source: Selected from data included with permission and copyrighted by Boots UK Limited. This copyrighted material is sourced from a licensed data provider and is not for distribution, except as may be authorised by the applicable terms of use.
CONDITIONS OF USE: The information in this database is intended to supplement, not substitute for, the expertise and judgement of healthcare professionals. The information is not intended to cover all possible uses, directions, precautions, drug interactions or adverse events, nor should it be construed to indicate that use of a particular medicine is safe, appropriate or effective for you or anyone else. A healthcare professional should be consulted before taking any medicine, changing any diet, or discontinuing any course of treatment.

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