Codeine (codeine phosphate) contains the active ingredient codeine and is used to reduce pain from headache, the flu and common cold. See here for more information and to order.
A: Mucinex contains the active ingredient guaifenesin, which is an expectorant that helps loosen phlegm and thin bronchial secretions. Mucinex does not have rapid heart rate as a possible side effect. There is a product called Mucinex-D that contains pseudoephedrine, and this ingredient can increase heart rate.
Drowsiness is found among people who take Mucinex, especially for people who are female, 60+ old , have been taking the drug for < 1 month, also take medication Synthroid, and have High blood pressure. This review analyzes which people have Drowsiness with Mucinex. It is created by eHealthMe based on reports of 9,781 people who have side effects when taking Mucinex from FDA, and is updated regularly.