Can regular Mucinex cause rapid heart rate?
• 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. Another commonly consumed substance that can increase heart rate is caffeine. Please see the following Everyday Health link for more information on Mucinex: http://www.everydayhealth.com/drugs/mucinex/side-effects.