Dextromethorphan-Guaifenesin Risks, Warnings, and Complications

SEROTONIN SYNDROME: Serotonin is a neurotransmitter (natural chemical) in the central nervous system which regulates mood. Too much serotonin can result in a rare but life-threatening condition called serotonin syndrome. Taking dextromethorphan and guaifenesin with certain other medications that affect serotonin levels, such as lithium, antidepressants, and certain anti-Parkinson's drugs, can increase the risk of serotonin syndrome. Give your doctor or pharmacist a complete list of your medications, including prescription drugs, over-the-counter medicines, dietary supplements, and herbal products, before starting dextromethorphan and guaifenesin so they can check for a dangerous drug interaction. Seek emergency medical attention if you develop fever, sweating, a fast heart rate, muscle spasms, muscle stiffness, and confusion. 

CHRONIC COUGH: Dextromethorphan and guaifenesin are for short-term treatment of cough. You should stop using this combination medicine and ask a doctor for advice if your cough lasts more than 7 days, keeps coming back, or you develop symptoms such as rash, fever, or persistent severe headache. These can be signs of more serious conditions. 

LUNG CONDITIONS: The drug combination of dextromethorphan and guaifenesin should not be used for chronic cough caused by smoking or lung conditions such as asthma, emphysema, and chronic bronchitis. Your healthcare practitioners will prescribe appropriate medications to treat these conditions. 

USE IN VERY YOUNG CHILDREN: Do not use dextromethorphan and guaifenesin in children under 4 years old. Talk to your child’s healthcare practitioners to discuss alternatives. The adult-strength products should not be used in children under 12 years old. Read the medication label carefully before giving this combination medication to a child. Do not exceed the recommended daily maximum dose. Check with licensed healthcare practitioners if you are not sure of the correct dosage for your child. Make sure you do not exceed the recommended maximum dose from multiple cough and cold medicines. 

MISUSE AND OVERDOSE: Taking too much dextromethorphan can lead to serious problems, including breathing problems, seizures, and coma. Keep in mind that dextromethorphan is found in many OTC cough or cold products. Read the label of each cough or cold medicine carefully to make sure you do not exceed the recommended maximum daily dose of this medication. Misuse of dextromethorphan, especially by teenagers, can lead to an overdose. Many pharmacies store products containing dextromethorphan behind the counter and only sell it to people over 18 years of age. Keep all medications, including over-the-counter products like dextromethorphan and guaifenesin, safely out of reach of children and adolescents.

PHENYLKETONURIA: Some products, such as the dissolvable granules of guaifenesin and dextromethorphan (Children's Mucinex Cough Mini-Melts), contain phenylalanine and can be dangerous for people with phenylketonuria (PKU). However, the syrup and regular tablets are safe. 

ALLERGIC REACTIONS: A severe allergic reaction to guaifenesin or dextromethorphan can lead to life-threatening anaphylaxis (closing of the throat). Call 911 if this happens. Seek emergency medical attention if you develop a skin rash, hives, itching, or swelling of the lips or tongue after using this medicine.