Codeine Side Effects

Medically reviewed by Drugs.com. Last updated on Apr 9, 2025.

Applies to codeine: oral tablet.

Precautions

It is very important that your doctor check your progress while you are using this medicine, especially within the first 24 to 72 hours of treatment. This will allow your doctor to see if the medicine is working properly and to decide if you should continue to use it. Blood tests may be needed to check for unwanted effects.

Do not use this medicine if you are using or have used an MAO inhibitor (MAOI) including isocarboxazid [Marplan®], linezolid [Zyvox®], phenelzine [Nardil®], selegiline [Eldepryl®], tranylcypromine [Parnate®]) within the past 14 days.

Check with your doctor before using this medicine with alcohol or other medicines that affect the central nervous system (CNS). The use of alcohol or other medicines that affect the CNS with codeine may worsen the side effects of this medicine, including dizziness, poor concentration, drowsiness, unusual dreams, and trouble with sleeping. Some examples of CNS depressants are antihistamines or medicine for hay fever, allergies, or colds, sedatives, tranquilizers, or sleeping medicines, medicine for depression, medicine for anxiety, prescription pain medicine or narcotics, medicine for attention deficit and hyperactivity disorder, medicine for seizures or barbiturates, muscle relaxants, or anesthetics (numbing medicines), including some dental anesthetics. This effect may last for a few days after you Stop taking codeine.

This medicine may be habit-forming. If you feel that the medicine is not working as well, do not use more than your prescribed dose. Call your doctor for instructions.

If you think you or someone else may have taken an overdose of this medicine, get emergency help at once. Your doctor may also give naloxone to treat an overdose. Signs of an overdose include: cold, clammy skin, coughing that sometimes produces a pink frothy sputum, dark urine, difficult or trouble breathing, irregular, fast or slow, or shallow breathing, nausea or vomiting, pain in the upper stomach, pale or blue lips, fingernails, or skin, pinpoint pupils of the eyes, or yellow eyes or skin.

This medicine may cause sleep-related breathing problems (eg, sleep apnea, sleep-related hypoxemia). Your doctor may decrease your dose if you have sleep apnea (stop breathing for short periods during sleep) while using this medicine.

Dizziness, lightheadedness, or fainting may occur when you get up suddenly from a lying or sitting position. Getting up slowly may help. Also, lying down for a while may relieve dizziness or lightheadedness. If this problem continues or gets worse, check with your doctor right away.

This medicine may make you dizzy, drowsy, confused, or disoriented. Do not drive or do anything else that could be dangerous until you know how this medicine affects you.

Using narcotics for a long time can cause severe constipation. To prevent this, your doctor may direct you to take laxatives, drink a lot of fluids, or increase the amount of fiber in your diet. Be sure to follow the directions carefully, because continuing constipation can lead to more serious problems.

Do not change your dose or suddenly stop using this medicine without first checking with your doctor. Your doctor may want you to gradually reduce the amount you are using before stopping it completely. This may help prevent worsening of your condition and reduce the possibility of withdrawal symptoms, including anxiety, fever, nausea, runny nose, stomach cramps, sweating, tremors, or trouble with sleeping.

Using this medicine while you are pregnant may cause serious unwanted effects, including neonatal withdrawal syndrome in your newborn baby. Tell your doctor right away if you think you are pregnant or if you plan to become pregnant while using this medicine.

Codeine is changed to morphine in the body. Some people change codeine to morphine more quickly than others. These individuals are called "ultra-rapid metabolizers of codeine". Contact your doctor immediately if you experience extreme sleepiness, confusion, or shallow breathing. These symptoms may indicate that you are an "ultra-rapid metabolizer of codeine". As a result, there is too much morphine in the body and more side effects of morphine than usual. Children may be especially sensitive to this effect. Do not give this medicine to:

• Children younger than 12 years of age.
• Children younger than 18 years of age who have had surgery removal of tonsils or adenoids.
• Children 12 to 18 years of age who have a high risk for breathing problems (eg, obstructive sleep apnea, obesity, lung disease).

If a nursing mother is an ultra-rapid metabolizer of codeine, it could lead to a morphine overdose in the nursing baby and cause very serious side effects.

For nursing mothers taking this medicine:

• Talk to your doctor if you have any questions about taking codeine or about how this medicine may affect your baby.
• Call your doctor if you become extremely tired and have difficulty caring for your baby.
• Your baby should generally nurse every 2 to 3 hours and should not sleep more than 4 hours at a time.
• Check with your doctor, hospital emergency room, or local emergency services (eg, "call 9-1-1") immediately if your baby shows signs of increased sleepiness (more than usual), difficulty breastfeeding, difficulty breathing, or limpness. These may be symptoms of an overdose and need immediate medical attention.

This medicine may cause adrenal gland problems. Check with your doctor right away if you have darkening of the skin, diarrhea, dizziness, fainting, loss of appetite, mental depression, nausea, skin rash, unusual tiredness or weakness, or vomiting.

Check with your doctor right away if you have anxiety, restlessness, a fast heartbeat, fever, sweating, muscle spasms, twitching, nausea, vomiting, diarrhea, or see or hear things that are not there. These may be symptoms of a serious condition called serotonin syndrome. Your risk may be higher if you also take certain other medicines that affect serotonin levels in your body.

Using too much of this medicine may cause reduced infertility (unable to have children). Talk with your doctor before using this medicine if you plan to have children.

Do not take other medicines unless they have been discussed with your doctor. This includes prescription or nonprescription (over-the-counter [OTC]) medicines and herbal or vitamin supplements.

Common side effects of codeine

Some side effects of codeine may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

Serious side effects of codeine

Along with its needed effects, codeine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur while taking codeine:

Get emergency help immediately if any of the following symptoms of overdose occur while taking codeine:

Symptoms of overdose

• bluish lips or skin
• chest pain or discomfort
• cold, clammy skin
• constricted, pinpoint, or small pupils (black part of the eye)
• coughing that sometimes produces a pink frothy sputum
• decreased awareness or responsiveness
• extreme sleepiness or unusual drowsiness
• increased sweating
• irregular, fast or slow, or shallow breathing
• pale or blue lips, fingernails, or skin
• slow or irregular heartbeat
• swelling in the legs and ankles

For healthcare professionals

Applies to codeine: compounding powder, injectable solution, oral solution, oral tablet.

General adverse events

The most frequently observed adverse reactions include drowsiness lightheadedness, dizziness, sedation, shortness of breath, nausea, vomiting, sweating, and constipation.^[Ref]

Respiratory

• Uncommon (0.1% to 1%): Bronchospasm, laryngospasm, respiratory depression
• Frequency not reported: Respiratory arrest, dyspnea
• Postmarketing reports: Deaths due to respiratory depression^[Ref]

Respiratory depression resulting in death has been reported in children who received codeine postoperatively following tonsillectomy and/or adenoidectomy. These children had evidence of being ultra-rapid metabolizers of codeine. Death has also been reported in nursing infants exposed to high levels of morphine in breast milk due to their breastfeeding mother being an ultra-rapid metabolizer of codeine.^[Ref]

Cardiovascular

• Uncommon (0.1% to 1%): Heartbeat irregularities, blood pressure changes, syncope
• Frequency not reported: Flushing, hypotension, palpitations, circulatory depression, shock, cardiac arrest, circulatory depression, bradycardia, tachycardia, edema^[Ref]

Nervous system

• Common (1% to 10%): Drowsiness, dizziness
• Uncommon (0.1% to 1%): Headache, lightheadedness, feeling faint, paradoxical CNS stimulation (especially in children), disorientation, restlessness, shakiness, somnolence, weakness
• Frequency not reported: Seizures^[Ref]

Other

• Frequency not reported: Fatigue, vertigo, malaise, hypothermia, fever, addiction, tolerance, dependence, withdrawal reactions upon discontinuation of chronically administered drug included diarrhea, sweating, vomiting, insomnia, agitation, tremor, body aches, gooseflesh, loss of appetite, nervousness or restlessness, runny nose, sneezing, shivering, stomach cramps, nausea, sleep disturbances, yawning, weakness, tachycardia, fever, irritability, mydriasis^[Ref]

Hypersensitivity

• Uncommon (0.1% to 1%): Itching, facial swelling, pruritus, urticaria, histamine release (hypotension, sweating, flushing of the face, tachycardia, breathlessness)
• Frequency not reported: Allergic reactions including maculopapular rash^[Ref]

Gastrointestinal

• Common (1% to 10%): Constipation
• Uncommon (0.1% to 1%): Dry mouth, loss of appetite, nausea, vomiting, paralytic ileus, toxic megacolon, anorexia, stomach cramps
• Frequency not reported: Gastrointestinal distress, anorexia, diarrhea, pancreatitis^[Ref]

Hepatic

• Frequency not reported: Biliary spasm^[Ref]

Genitourinary

• Uncommon (0.1% to 1%): Urinary retention or hesitance, ureteric spasm, reduced libido and/or potency^[Ref]

Dermatologic

• Uncommon (0.1% to 1%): Rash
• Frequency not reported: Sweating, urticaria, pruritus^[Ref]

Ocular

• Uncommon (0.1% to 1%): Miosis, blurred or double vision
• Frequency not reported: Visual disturbances^[Ref]

Endocrine

• Uncommon (0.1% to 1%): Antidiuretic effect
• Frequency not reported: Decreased libido or potency, erectile dysfunction, sexual dysfunction^[Ref]

Psychiatric

• Uncommon (0.1% to 1%): Euphoria, dysphoria, unusual dreams, hallucinations, insomnia, anxiety
• Frequency not reported: Mood changes, restlessness, confusion, mental depression^[Ref]

Metabolic

• Frequency not reported: Hyperglycemia, anorexia^[Ref]

See also:

Frequently asked questions

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Further information

Codeine side effects can vary depending on the individual. Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Note: Medication side effects may be underreported. If you are experiencing side effects that are not listed, submit a report to the FDA by following this guide.

Medical Disclaimer