Guaifenesin

Absorption

Studies have shown that guaifenesin is well absorbed from and along the gastrointestinal tract after oral administration .

Toxicity

The most prevalent signs and symptoms associated with an overdose of guaifenesin have been nausea and vomiting .
Although adequate and well-controlled studies in pregnant women have not been performed, the Collaborative Perinatal Project monitored 197 mother-child pairs exposed to guaifenesin during the first trimester . An increased occurrence of inguinal hernias was found in the neonates . However, congenital defects were not strongly associated with guaifenesin use during pregnancy in 2 large groups of mother-child pairs .
Moreover, guaifenesin is excreted in breast milk in small quantities . Subsequently, caution should be exercised by balancing the potential benefit of treatment against any possible risks .
Additionally, an LD50 value of 1510 mg/kg (rat, oral) has been reported for guaifenesin .

Description

Guaifenesin was originally derived from the guaiac tree and used by Native Americans for health purposes. Synthesis of guaifenesin was first reported in 1912. Guaifenesin has been used in the treatment of respiratory diseases since the nineteenth century. The United States’ Food and Drug Administration (FDA) approved guaifenesin for use in overthe- counter medications in 1989. Guaifenesin is widely consumed alone and combined with antihistamines, cough suppressants, and decongestants. Guaifenesin is also a centrally acting muscle relaxant and is used routinely in combination with analgesics and sedatives in large-animal veterinary surgery.

Description

Guaifenesin is an expectorant found in over-the-counter cough and cold medicines such as Robitussin. By loosening phlegm and increasing lubrication in the lungs, it can allow for a productive cough and decreased chest congestion.

The Uses of Guaifenesin

Guaifenesin is commonly used as an expectorant.
Guaifenesin comes in tablet and capsule form, as syrup, as dissolving granules, and recently as an extended-release (longacting) tablet. The tablets, capsules, dissolving granules, and syrup are usually taken with or without food every 4 h as needed. The extended-release tablet is usually taken with or without food every 12 h.
In veterinary medicine, guaifenesin is given intravenously to induce muscle relaxation when administering anesthesia. It relaxes both laryngeal and pharyngeal muscles, allowing easier intubation. Guaifenesin is also used in the treatment of horses with exertional rhabdomyolysis and in dogs with strychnine intoxication.

Background

Guaifenesin possesses a storied history, having been originally formally approved by the US FDA in 1952 and continues to be one of very few - if not perhaps the only drug that is readily available and used as an expectorant . Since that time the agent has been a combination component of various prescription and non-prescription over-the-counter cough and cold products and is currently a widely available over-the-counter generic medication . Although it is principally believed that guaifenesin elicits an action to facilitate productive cough to manage chest congestion , it is not known whether the agent can reliably mitigate coughing.
Regardless, on March 1, 2007, the FDA received a petition asking the FDA to notify the public that some antitussives, expectorants, decongestants, antihistamines, and cough/cold combinations are not known to be safe and effective in children under the age of 6 years . After the negotiation between FDA and major manufacturers, a voluntary transition of labels for not using guaifenesin in children under the age of 4 years was endorsed by FDA in 2008 .
Furthermore, there has also been contemporary research to suggest that guaifenesin possesses and is capable of demonstrating anticonvulsant and muscle relaxant effects to some degree possibly by acting as an NMDA receptor antagonist .

Indications

Guaifenesin is an expectorant that is indicated for providing temporary symptomatic relief from congested chests and coughs which may be due to a cold, bronchitis, and/or other breathing illnesses .

What are the applications of Application

Guaifenesin is a compound with expectorant and sedative properties

Pharmacokinetics

Guaifenesin is categorized as an expectorant that acts by enhancing the output of phlegm (sputum) and bronchial secretions via decreasing the adhesiveness and surface tension of such material . Furthermore, guaifenesin elicits an increased flow of less viscous gastric secretions that subsequently promote ciliary action - all actions that ultimately change dry, unproductive coughing to coughs that are more productive and less frequent . Essentially, by decreasing the viscosity and adhesiveness of such secretions, guaifenesin enhances the efficacy of mucociliary activity in removing accumulated secretions from the upper and lower airway .

Metabolism

After the oral administration of 400 mg guaifenesin, the agent experiences rapid hydrolysis (more than 60% of the dose hydrolyzed over a range of seven hours) with β-(2-methoxyphenoxy)-lactic acid found as the major urinary metabolite but no parent drug detectable in the urine . Moreover, it has been observed that guaifenesin also experiences both oxidation and demethylation . In particular, the medication is quickly metabolized hepatically by way of oxidation to β-(2-methoxyphenoxy)-lactic acid . Furthermore, guaifenesin is also demethylated by O-demethylase in liver microsomes to the point where about 40% of an administered dose is excreted as this metabolite in the urine within 3 hours . In fact, O-demethylase appears to be the primary enzyme for the metabolism of guaifenesin and the primary metabolites of the substance are β-(2-methoxyphenoxy)-lactic acid and the demethylated hydroxyguaifenesin, both of which are themselves inactive moieties .