Mucinex Sinus-Max Severe Congestion Relief Caplets fights mucus, sinus pressure, and headache, so your worst symptoms don't get the best of you. Mucinex Sinus-Max Severe Congestion Relief has a triple-action formula that contains three maximum strength medicines.* Acetaminophen relieves pain and headaches, Guaifenesin works as an expectorant and thins and loosens mucus, and Phenylephrine HCl works as a nasal decongestant and reduces swelling in the nose that causes sinus pressure.