The appropriate dosage for Mucinex DM is one or two tablets every 12 hours for adults and children who are 12 years and older. It should be taken with a full glass of water. The maximum dosage is four tablets in 24 hours, according to Drugs.com.
Mucinex DM is an over-the-counter medicine that helps loosen phlegm, reduces bronchial secretions and encourages productive coughing. It also temporarily relieves coughing caused by the common cold or irritants. Patients who suffer from a chronic or persistent cough should not take this medicine.
An overdose on Mucinex DM may cause serious side effects including brain damage, seizure and even death, as stated by WebMD.