When taking Mucinex or other products containing guaifenesin, patients should first consult with a doctor or pharmacist to ensure that guaifenesin does not interact with other medications they are taking, explains MedlinePlus. Patients must not take too much guaifenesin or take the medication more often than directed. Patients who are taking Mucinex with different types of cough or cold medications should check the labels carefully to make sure the medications do not contain the same active ingredients.
Mucinex and other medications containing guaifenesin may cause side effects, such as headache, nausea and vomiting, according to MedlinePlus. Because guaifenesin may cause severe and potentially life-threatening side effects in young children, this medication is not recommended for children under 4 years old. Children between the ages of 4 and 11 years may take guaifenesin, but the adult administering the medication must ensure that the child receives the proper dose. Children must never take guaifenesin products that are formulated for adults.
Guaifenesin is an expectorant that relieves chest congestion. It works by thinning mucus in the airways, allowing the patient to cough up the mucus and clear the breathing passages, states MedlinePlus. While guaifenesin helps reduce symptoms, it does not make a patient's recovery from illness faster. Patients who continue having symptoms after taking guaifenesin for seven days should contact a doctor for evaluation.