Guaifenesin (pronounced /ɡwaɪˈfɛnɨsɪn/) (INN) or guaiphenesin (former BAN), also glyceryl guaiacolate, is an expectorant drug sold over the counter and usually taken by mouth to assist the bringing up (expectoration) of phlegm from the airways in acute respiratory tract infections.
Availability
Guaifenesin is sold as pills or syrups under many brand names. Single ingredient formulations of guaifenesin are available, and it is also included in many other over-the-counter cough and cold remedy combinations (usually in conjunction with dextromethorphan and/or pseudoephedrine or phenylephrine and/or acetaminophen). Guaifenesin is a component of Mucinex, Robitussin DAC, Cheratussin DAC, Robitussin AC, Cheratussin AC and Bidex 400.
In certain jurisdictions, guaifenesin is available over-the-counter in combination with codeine to be sold at a pharmacist's discretion, though many pharmacists decline to do so.
Uses
The principal use of guaifenesin is in the treatment of coughing, but the drug has numerous other uses, including medical, veterinary, and personal.
Mechanism of action & effect
Guaifenesin is thought to act as an expectorant by increasing the volume and reducing the viscosity of secretions in the trachea and bronchi. Thus, it may increase the efficiency of the cough reflex and facilitate removal of the secretions; however, objective evidence for this is limited and conflicting.
Treatment of coughing
A Cochrane Collaboration meta-analysis of over the counter medicines for acute cough in children and adults found no evidence for the effectiveness of any examined drug other than guaifenesin; evidence for guaifenesin was ambiguous.[2] Guaifenesin is sometimes combined with dextromethorphan, an antitussive. In normal use this combination is believed[who?] to produce fewer, but more productive coughs.
Treatment of asthma
Guaifenesin is effective in the treatment of the thickened bronchial mucosa characteristic of asthma.[citation needed] It works by drawing water into the bronchi. The water both thins mucus and lubricates the airway, facilitating the removal of mucus by coughing.
Treatment of gout
Guaifenesin is a uricosuric, increasing excretion of uric acid from the blood serum into the urine.[3] This fact was discovered by chance, during a survey of hypouricemia in hospital inpatients.[4] Compared to other uricosuric drugs used to treat gout, guaifenesin is relatively mild.
Treatment of fibromyalgia
Because of its uricosuric effect, guaifenesin was chosen in the 1990s for the experimental guaifenesin protocol – a treatment for fibromyalgia. Proponents[who?] of the guaifenesin protocol believe that it treats fibromyalgia by removing excess phosphate from the body. However, a consumer alert on the Fibromyalgia Network's website (http://www.fmnetnews.com/resources-alert-product6.php) states that Dr. St. Amand's claims of guaifenesin's effects on fibromyalgia are groundless, and cites double blind research by Robert Bennett, M.D. which found no significant differences between guaifenesin and a placebo in terms of any effect on fibromyalgia or its markers.
Use to facilitate conception
Guaifenesin is widely used by women to facilitiate conception by thinning and increasing the amount of cervical mucus.[5] Evidence concerning the effectiveness of this use is almost entirely anecdotal; the exception[6] is a very small study without controls. One investigator[7] regards guaifenesin as the simplest but least effective method of improving cervical mucus.
Following a medical article in Czech about guaifenesin in the treatment of primary dysmenorrhea, another very small but double-blind and placebo-controlled experiment[9] found that guaifenesin reduced primary dysmenorrhea, but the effect was not significant.
Use by singers
Opera singers sometimes refer to guaifenesin as the "wonder drug" for its ability to promote secondary mucosal secretion in the respiratory system. Secondary mucus is the thinner, lubricating mucus that occurs on the vocal folds naturally when they are healthy and well hydrated. Singers use guaifenesin to improve the state of their vocal folds in extremes of humidity (very humid or very dry), after flying long distances, and during mild allergies
Other uses
Guaifenesin also has other known neurological effects, including an analgesic effect that is related to its action as a skeletal muscle relaxant, and possible inhibition of platelet aggregation.
Side effects
Consumption of guaifenesin in above-normal quantities has the potential to cause side effects. Known side effects include nausea, vomiting, and (rarely) the formation of kidney stones of uric acid (uric acid nephrolithiasis).[11] Nausea and vomiting can be reduced by taking guaifenesin with meals.[1] The risk of forming kidney stones can be reduced by maintaining good hydration and increasing the pH of urine (see Uric acid nephrolithiasis). Rarely, severe allergic reactions may occur, including a rash or swelling of the lips or face, which may require urgent medical assistance. Mild dry mouth or chapped lips may also occur when taking this medication. Drinking a glass of water is recommended each time one takes guaifenesin.[12] Water helps to reduce dry mouth, chapped lips, and the risk of kidney stones, and increases the effectiveness of the drug in hydrating mucus.
Veterinary use
Guaifenesin's neurological properties first became known in the late 1940s, and it is widely used in veterinary medicine to induce and maintain anesthesia in horses[13][14] and llamas.[15] In contrast to other propanediol drugs used for this purpose, guaifenesin has less hemolytic activity (i.e., less destruction of red blood cells) and is more soluble in water.