Table 1.

Brief history of guaifenesin and its regulatory path in the US

Time	Key events
Pre-1500s	Used as natural remedy by Native Americans
1500s	Guaiac extract used as stimulant remedies, e.g. for sore throat, syphilis
1800s	Guaiac extract used to treat respiratory diseases in Europe
1952	First accepted by US Food and Drug Administration (FDA)
1989	Guaifenesin was reclassified to Category I (generally recognized as safe and effective) and was included in the Final Monograph (Cold, Cough, Allergy, Bronchodilator, and Antiasthmatic Drug Products for Over-the-Counter Human Use, 21 CFR 341) as an expectorant for the symptomatic treatment of colds and stable chronic bronchitis.
2002	12-h extended-release (ER) guaifenesin bi-layer tablets were approved by the FDA. From 2007, the FDA removed all marketed, but unapproved, timed-release guaifenesin products from the market.