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The cold season is upon us.

The colder month allow us to come together, whether it be in school, at the office, or at home. Those of us that do not brave the cold seem to confine ourselves to close quarters and this closeness allows the spread of germs. The common cold is described as a nonbacterial upper respiratory tract infection, with common clinical manifestations such as general malaise, and a runny, stuffy nose. Other symptoms may include sneezing, possible sore throat, cough, and possibly some chest discomfort. This article will discuss what agents are available to treat the common cold and why these agents are similar to what we utilize in respiratory care.


Sympathomimetic (adrenergic) agents are commonly used to treat bronchospasm. This is intention is due to its beta 2 effect on the airwary. However, in cold agents, sympathomimetics are intended for a decongestant effect, which is based on their alpha stimulating property and resulting vasoconstriction.

Sympathomimetics such as pseudoephedrine are found under brand names such as Sudafed and can be taken orally. Because of changes in the U.S. Patriot Act single agents or combination drugs using pseudoephedrine are placed behind the counter and regulated sales documented, because the drug was being overpurchased for use in methamphetamines. In some states you must have a prescription from a licensed physician to obtain over the counter pseudoephedrine. Pharmaceutical companies have turned to phenylephrine as a substitute, however, the U.S. Food and Drug Administration approved dose of 10 mg has little effect on nasal decongestion when used orally because of the drug's high first-pass effect. This agent is common under the name PE, for example Sudafed PE. In a study by McLaurin and associatesl it was found that 10 mg of phenylephrine was no more effective than placebo. Oxymethazoline, a sympathomimetic with brand names such as Afrin can be used topically for the nasal mucosa. In general, topical applications require lower dosages than oral use. Much as the same with inhaled agents. Topical sympathomimetic decongestant sprays or drops produce results faster than oral applications. However, repeated use can cause the mucosa to swell, which is known as rebound congestion. Rebound nasal congestion occurs with overuse of these agents, the result of which is that the vasoconstriction does not occur.

Systemic, compared with topical, application has the advantage of giving more extensive decongestant effects involving deeper blood vessels. However, producing nasal vasoconstriction through systemic routes will often lead to other systemic effects of sympathomimetics, such as a rise in blood pressure and increased heart rate.

First-generation antihistamines, such as Benadryl and Tavist are non-selective agents. These agents will have a primary effect, however, the will produce drowsiness. Many times these agents are used as a sleep aid. Look at your local pharmacy and pick up a bottle of Benadryl and a generic sleep aid. The ingredients will be the same, diphenhydramine. Second-generation antihistamines, such as Allegra and Zyrtec are longer acting and non-sedating.

Antihistamines have three major classes of effects, antihistaminic, sedative, and anticholinergic activity. Second-generation agents are selective for H1 receptors and are less sedating than first-generation agents. Antihistaminic activity blocks the increased vascular permeability and bronchial smooth muscle constriction caused by histamine. These actions are the reason antihistamines are used to treat allergic disorders such as allergic rhinitis.

The sedative effect of antihistamines is thought to be caused by penetration of the agents into [he brain and block receptors causing drowsiness. There is also antagonism of other central nervous system receptors, such as serotonin and acetylcholine.

An anticholinergic effect produces considerable upper airway drying, just as would occur with an antimuscarinic agent such as atropine sulfate. In addition, effects seen with cholinergic blockade may occur, including central nervous system effects of stimulation, anxiety, and nervousness, as well as peripheral effects of dilated pupils, blurred vision, urinary retention, and constipation.

One of the beneficial effects of antihistamine use with a cold is the drying of upper airway secretions, which lessens the rhinitis and accompanying sneezing. There is some question whether the drying of secretions is due to histamine antagonism or to the anticholinergic effect of these agents. How much histamine release occurs with colds is debated. In allergic rhinitis, there is no question that histamine causes much of the inflammatory response, and in fact the newer long-acting agents are particularly helpful with this condition. Blockade of H1 receptors prevents the histamine contribution to the symptoms of nasal itching, congestion, sneezing, rhinorrhea, and ocular irritation.

Expectorants are agents that facilitate removal of mucus from the lower respiratory tract. An example is guaifenesin, which is thought to reduce the adhesiveness and surface tension of mucus, and thus increase the movement and clearance of the secretions. Because mucus is mostly water the intake of fluid is essential in the treatment of a cold. Guaifenesin may help by reducing the surface tension of the mucus, however, in studies it has not been effective in the treatment of persons with pulmonary disease due to the production of sputum, which contains more than mucus.

Coughing is a defense mechanism to protect the upper airway from irritants such as dust particles or aerosols, liquids, and other foreign objects. This mechanism is a reflex, coordinated by a postulated cough center in the medulla. For some with a cold a cough can be irritating and interfere with sleep.

Cough suppressants ad by depressing the cough center in the medulla. Narcotics exert a powerful depressant effect on the medullary centers and are often used for this purpose. Common agents are codeine or hydrocodone. A commonly used nonnarcotic is dextromethorphan. Both dextromethorphan and codeine are available in OTC preparations. The need for a prescription antitussive is unusual, especially in a cold, with the availability of OTC preparations.

Cough suppres are helpful and indicated to suppress dry, hacking, nonproductive irritating coughs, especially if the coughing causes sleep loss. Furthermore, a constant nonproductive cough can cause irritation of the trachea, leading to more coughing. Do not suppress the cough reflex in the presence of copious bronchial secretions that need to be cleared. This includes situations of cystic fibrosis and other chronic obstructive lung diseases such as bronchitis. Excess mucus secretions from the lower respiratory tract are not present in an uncomplicated cold and indicate the need for further evaluation and possible treatment with an antibiotic. The combination of an expectorant and an antitussive in a cold medication is questionable. This amounts to suppressing the clearance mechanism while stimulating secretions to be cleared. Use of a single-entity cough preparation to treat a dry, irritating cough is recommended.

Because compounds change fairly rapidly, no list remains current in terms of what is on the market. However, the basic principle of the typical four classes of ingredients remains, and new compounds can be evaluated for particular uses by considering the effects of these four classes of agents. Many compounds are available as OTC preparations, thus requiring no prescription. The possibility of overdosing and abuse by combining prescribed compounds and OTC compounds is very real. Often OTC preparations have the same classes of ingredients but in lower concentrations.

There is no cure for the common cold, and the four classes of drugs used in cold remedies treat only symptoms. Furthermore, their potentially undesirable effects should be considered. Fluids and rest remain a basic and rational approach to surviving colds and preventing spread of the rhinovirus, but is probably the least feasible for current lifestyles. Be safe and be current, look at what OTC agent you put into your body.

Douglas Gardenhire is a veteran therapist, author, educator and the Director of Clinical Education in the RC Program at GA State University.

By Doug Gardenhire MS, RRT-NPS
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Author:Gardenhire, Doug
Publication:FOCUS: Journal for Respiratory Care & Sleep Medicine
Article Type:Disease/Disorder overview
Geographic Code:1USA
Date:Sep 1, 2010
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