A cough is a common symptom of viral respiratory infections and allergies. A cough can also be caused by other conditions, some of them serious. For example, a cough can be a symptom of asthma, acid reflux into the esophagus (gastroesophageal reflux disease or GERD), sinusitis, postnasal drip, bronchitis, cigarette smoking, pneumonia, tuberculosis, hypersensitivity pneumonia (inflammation of the lung from exposure to certain environmental chemicals), and even lung cancer. Therefore, a persistent cough or a cough that is associated with chest pain, fever, weight loss, or blood-tinged or discolored sputum should be evaluated by a doctor.
There are three types of cough medications available OTC for the temporary relief of cough due to a cold. They are oral cough suppressants, oral expectorants, and topical (externally applied) medicines.
Oral cough suppressants
Codeine and hydrocodone are narcotic oral cough suppressants that require a doctor's prescription. Dextromethorphan is an oral cough suppressant that is available OTC. Dextromethorphan is chemically related to codeine and acts on the brain to suppress cough, but it does not have the pain-relieving and addictive properties of codeine. Diphenhydramine is another non-narcotic medication that acts on the brain to suppress cough. It is also an antihistamine.
Dextromethorphan and diphenhydramine can be used to relieve a dry, hacking cough. They are not generally used to suppress a productive cough (when sputum is coughed up). Suppressing a productive cough impairs the clearing of secretions and mucous from the airways, which is generally undesirable. However, cough suppressants are sometimes used to suppress even productive coughs if they are especially bothersome and prevent restful sleep.
Guaifenesin is an oral expectorant that is believed to increase the leaking of fluid out of the lung tissue and into the airways. This action thins (liquefies) the thick mucus in the airways and facilitates the clearing of the mucous by coughing. Clearing of mucous from the airways decreases cough.
Camphor and menthol are topical cough medications. Camphor and menthol ointments are rubbed on the throat and the chest as a thick layer. The anesthetic action of their vapors is believed to relieve cough. They are also available as products for steam inhalation. Menthol is also available as lozenges and compressed tablets.
Examples of products in the cough category include the following:
Cough suppressants: Buckley's Mixture, Diabe-Tuss DM, and St Joseph Cough Suppressant for Children and Delsym (effective for 12 hours)
Expectorant: Hytuss, Robitussin, Mucinex, Duratuss G, Muco-Fen
Topical cough medicines: Hall's Mentho-Lyptus Cough Suppressant Drops, Mentholatum, Vick's VapoRub, and Vick's VapoSteam
Cough suppressant plus an expectorant and other cold/flu/allergy ingredients: Alka-Seltzer Plus Cold and Cough, Alka-Seltzer Plus Cold and Flu, Comtrex Deep Chest Cold & Congestion Relief, Coricidin HBP Cough and Cold Tablets, Dimetapp Cold and Cough Liqui-Gels Maximum Strength, PediaCare Cough-Cold Liquid and Chewable Tablets, Robitussin Maximum Strength Cough and Cold, TheraFlu Flu Cold and Cough Medicine, and Triaminic AM Cough and Decongestant formula
Since many of these combinations also contain an antihistamine, a decongestant, and an analgesic in addition to the cough suppressant and expectorant, they also provide relief of nasal congestion, sneezing, fever, and aches.
In October 2000, an advisory panel of the U.S. Food and Drug Administration (FDA) recommended that phenylpropanolamine (PPA), an ingredient contained in many OTC and prescription cold medications as well as weight-loss products, be classified as unsafe because of reports of stroke associated with the ingredient. It was removed from OTC sale in 2005 in the U.S.