In brief: Mucinex.
Mucinex is the old drug guaifenesin in an new FSA-approved OTC extended-release formulation. In recommended dosages, it is generally regarded as safe. Medical Letter consultants have not been impressed by guaifenesin's effectiveness in older formulations.
D003692:Delayed-Action Preparations; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D006140:Guaifenesin / Q000008:administration & dosage* / Q000191:economics; D006801:Humans
D003692:Delayed-Action Preparations; D006140:Guaifenesin