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What is codeine?

Codeine is an opioid medicine used to treat pain. Codeine is also used to suppress cough. It is available as 15-mg, 30-mg, and 60-mg tablets. All are taken by mouth. Codeine also can be combined with other medicines, such as:

  • Acetaminophen (Tylenol® with codeine), to control pain (available in liquid and tablet form)
  • Guaifenesin, to suppress cough (available in liquid form)
  • Promethazine, to suppress cough (available in liquid form)

Laboratory testing

An enzyme in the body called cytochrome P450 2D6 (CYP2D6) has the ability to break down certain medicines including codeine. A genetic test can be done to determine if your CYP2D6 breaks down medicines slower or faster than normal. If your body breaks down the medicine slower or faster than normal, you should avoid taking codeine. For information about CYP2D6 and its effect on codeine, talk with your doctor or pharmacist, and see “Do you know… Cytochrome P450 2D6 (CYP2D6) and medicines.” For more details, go to

Possible side effects of codeine


  • Feeling drowsy
  • Nausea
  • Slower than normal rates of breathing
  • Low blood pressure

Later (more than a day after treatment starts)

  • Constipation (hard to have bowel movement)
  • Itching and hives
  • Feeling drowsy or very sleepy
  • Feeling dizzy
  • Nausea and vomiting
  • Mood changes (feeling sadder or happier)
  • Dry mouth
  • Fainting
  • Problems urinating

These are the most common side effects, but there may be others. Please report all side effects to the doctor or nurse.

In case of a severe side effect or reaction, call the doctor, nurse or pharmacist at 901-595-3300. If you are outside the Memphis area, dial toll-free 1-866-2STJUDE (1-866-278-5833), and press 0 once the call is connected.

Special instructions for codeine

  • If you have any of the side effects listed above, most should get better after you have taken codeine for a few of days. Tell your doctor if the side effects get worse while you are taking this medicine. It may mean you need less codeine.
  • If you are taking this medicine on a regular basis, do not stop taking it until the doctor tells you to do so. Stopping codeine without slowly decreasing the dose can lead to diarrhea, headache, sweating, muscle cramps, nausea, vomiting, or problems sleeping and resting.
  • This medicine may cause you to feel dizzy and drowsy. Do not operate heavy equipment or drive a car until you see how this medicine affects you.
  • If you have not slept well because of your pain, you may sleep more during the first few days of taking this medicine to “catch up” on missed sleep.
  • If you are taking this medicine regularly, then you should drink more fluids and eat more fiber to help prevent constipation. Tell your doctor or nurse if you have not had a bowel movement in 3 to 5 days. You may need to take a stool softener or laxative to relieve your constipation.
  • If you have taken codeine for a long time, at some point your doctor will slowly decrease your dose to wean you off the medicine. During this time, watch for a sudden onset of diarrhea, headache, sweating, muscle cramps, nausea, vomiting, or trouble sleeping and resting. If this occurs, call your doctor right away. It could mean your dose is being lowered too fast.
  • If you are taking combined drugs (codeine plus acetaminophen, guaifenesin, or promethazine), you should avoid taking other medicines that contain acetaminophen, guaifenesin, or promethazine. For example, do not take acetaminophen (Tylenol®) while taking Tylenol with Codeine®. Taking both medicines at the same time could result in a Tylenol® dose that is too high.
  • Other medicines can increase the drowsy feeling caused by codeine. These include:
    • Alcohol (found in many over-the-counter cough and cold medicines),
    • Diphenhydramine (over-the-counter Benadryl®);
    • Promethazine;
    • Diazepam or lorazepam;
    • Antidepressants, such as amitriptyline; and
    • Medicines used to treat seizures (such as carbamazepine, phenytoin, gabapentin, phenobarbital, and valproic acid).
  • Always tell your doctor if you are taking any of these medicines, or if you start taking any new medicine while you are taking codeine.


This document is not intended to take the place of the care and attention of your personal physician or other professional medical services. Our aim is to promote active participation in your care and treatment by providing information and education. Questions about individual health concerns or specific treatment options should be discussed with your physician.

St. Jude complies with health care-related federal civil rights laws and does not discriminate on the basis of race, color, national origin, age, disability, or sex.

ATTENTION: If you speak another language, assistance services, free of charge, are available to you. Call 1-866-278-5833 (TTY: 1-901-595-1040).

ATENCIÓN: si habla español, tiene a su disposición servicios gratuitos de asistencia lingüística. Llame al 1-866-278-5833 (TTY: 1-901-595-1040).

تنبيه: إذا كنت تتحدث باللغة العربية فيمكنك الاستعانة بخدمات المساعدة اللغوية المتوفرة لك مجانا. .يرجى الاتصال بالرقم. 5833-278-866-1  (الهاتف النصي: 1040-595-901-1).