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Codar GF Side Effects

Generic name: codeine / guaifenesin

Medically reviewed by Last updated on Feb 27, 2024.

Note: This document contains side effect information about codeine / guaifenesin. Some dosage forms listed on this page may not apply to the brand name Codar GF.

Applies to codeine / guaifenesin: oral liquid, oral solution, oral syrup.


For all patients taking this drug:
  • This drug has an opioid drug in it. Opioid drugs can put you at risk for addiction, abuse, and misuse. Misuse or abuse of this drug can lead to overdose and death. If you have questions, talk with your doctor.
  • This drug has an opioid drug in it. Severe side effects have happened when opioid drugs were used with benzodiazepines or other drugs that may make you drowsy or slow your actions. This includes slow or troubled breathing and death. Benzodiazepines include drugs like alprazolam, diazepam, and lorazepam. Benzodiazepines may be used to treat many health problems like anxiety, trouble sleeping, or seizures. If you have questions, talk with your doctor.
  • Many drugs interact with this drug and can raise the chance of side effects like deadly breathing problems. Talk with your doctor and pharmacist to make sure it is safe to use this drug with all of your drugs.
  • Avoid alcohol or other drugs and natural products that slow your actions.
  • Get medical help right away if you feel very sleepy, very dizzy, or if you pass out. Caregivers or others need to get medical help right away if the patient does not respond, does not answer or react like normal, or will not wake up.
  • Very bad and sometimes deadly breathing problems have happened with this drug. Talk with the doctor.
  • Get medical help right away if you have slow breathing, shallow breathing, or trouble breathing.
  • This drug is not for use in children younger than 18 years of age. The benefits of taking this drug for a cough due to allergies, a cold, or other infection do not outweigh the risks in children. If your child has been given this drug or if you have any questions, talk with your child's doctor.

Serious side effects of Codar GF

WARNING/CAUTION: Even though it may be rare, some people may have very bad and sometimes deadly side effects when taking a drug. Tell your doctor or get medical help right away if you have any of the following signs or symptoms that may be related to a very bad side effect:

Other side effects of Codar GF

All drugs may cause side effects. However, many people have no side effects or only have minor side effects. Call your doctor or get medical help if any of these side effects or any other side effects bother you or do not go away:

These are not all of the side effects that may occur. If you have questions about side effects, call your doctor. Call your doctor for medical advice about side effects.

You may report side effects to the FDA at 1-800-332-1088. You may also report side effects at

For Healthcare Professionals

Applies to codeine/guaifenesin: oral capsule, oral liquid, oral syrup, oral tablet.


The more commonly reported adverse effects of codeine include nausea, vomiting, and diarrhea. Guaifenesin is generally well tolerated.

Nervous system


Frequency not reported: CNS depression, lightheadedness, dizziness, sedation, headache, convulsions, weakness[Ref]



Frequency not reported: Tachycardia, bradycardia, palpitation, faintness, syncope, orthostatic hypotension, circulatory depression



Frequency not reported: Nausea, vomiting, constipation, biliary tract spasm, increased colonic motility, toxic dilation


Frequency not reported: Abdominal pain (upper), diarrhea, nausea, vomiting[Ref]



Frequency not reported: Oliguria, urinary retention, antidiuretic effect[Ref]



Frequency not reported: Rash


Frequency not reported: Rash[Ref]

Codeine-induced rash may be related to direct stimulation of histamine release.[Ref]



Frequency not reported: Pruritus, giant urticaria, angioneurotic edema, laryngeal edema


Frequency not reported: Hypersensitivity reactions (pruritus, urticaria)



Frequency not reported: Visual disturbances



Frequency not reported: Euphoria, dysphoria, transient hallucination, disorientation



Frequency not reported: Respiratory depression[Ref]

Respiratory depression and death have occurred in children who received codeine in the postoperative period following tonsillectomy and/or adenoidectomy. Further investigation has shown these patients to be ultra-rapid metabolizers of codeine. Children with obstructive sleep apnea who are treated with codeine appear to be particularly sensitive to the respiratory depressant effects of codeine.[Ref]


1. de Groot AC, Conemans J (1986) "Allergic urticarial rash from oral codeine." Contact Dermatitis, 14, p. 209-14

2. (2001) "Product Information. Robitussin (guaifenesin)." Wyeth-Ayerst Laboratories

3. Gonzalogarijo MA, Revengaarranz F (1996) "Fixed drug eruption due to codeine." Br J Dermatol, 135, p. 498-9

4. US Food and Drug Administration (2016) FDA News Release: FDA requires strong warnings for opioid analgesics, prescription opioid cough products, and benzodiazepine labeling related to serious risks and death from combined use.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.