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Guaifenesin Products—Available or Not?

Single-ingredient guaifenesin extended-release products have long been a mainstay for many clinicians. Until recently there have been many different products available, manufactured by many different pharmaceutical companies. As of December 1, 2003, all single-ingredient guaifenesin extended-release products, with the exception of Mucinex®, have been removed from the market.

In October 2002, the FDA sent warning letters to sixty-six companies about their marketing of single-release guaifenesin extended-release products. The products were being marketed without ever having applied for New Drug Applications (NDA), and therefore never having been FDA approved. The only manufacturer whom had submitted an NDA was the maker of Mucinex®, which was approved in July 2002 for over-the-counter use. The warning stated that all manufacturers of single-release guaifenesin extended-release products must submit an NDA and have their drug approved, or remove it from the market.

As a result of the FDA warning, many manufacturers decided to discontinue the marketing of their products instead of filing for an NDA. Many of these companies offer what most consider suitable alternatives—dual-ingredient guaifenesin extended-release products. For example, Humibid L.A.® has been reformulated to contain two expectorants, guaifenesin 600 mg and potassium guaiacolsulfonate 300 mg per tablet.

The new formulation of Humibid L.A. is thought to have similar efficacy to the older formulation, though there is no clinical evidence to lend credence. However, there are some known differences with the two products. Following the FDA warning in Fall 2003, the manufacturer of Humibid L.A.®, Celltech, sold the brand name rights (not the formulation) to Carolina Pharmaceuticals. Carolina Pharmaceuticals then reformulated the product and marketed it under the same name. The products should not be considered bioequivalent, though, since the ingredients are not the same. Celltech’s formulation of the drug contained 600 mg of guaifenesin per tablet and was dosed one to two tablets every 12 hours (maximum 2400 mg per day). The new Humibid L.A.® formulation is dosed one tablet every 12 hours, not to exceed two tablets in 24 hours (1800 mg total expectorant). The new formulation will remain a prescription product.

Prescribing clinicians need to be cautious when prescribing Humibid L.A.®, and pharmacists need to be sure to verify the correct dosing for the product.

References:

1. The Pharmacist’s Letter Online. http://www.pharmacistsletter.com. Detail-document #200102.
   
2. Drug Information Handbook. 2003-2003.