Treating an Acute Cough

Treatment of underlying conditions contributing to cough is paramount. For example, in gastroesophageal reflux disease, treatment of the reflux itself can alleviate associated cough. Smokers presenting with cough are prime candidates for discussing smoking cessation strategies.

A specific treatment is not always possible. For example, there is no cure for the viral infection that causes the common cold. Despite a lack of evidence to support their use, nonspecific treatments such as nonprescription antitussives and protussives (expectorants) are frequently used in these cases depending on the presence/absence of mucus (sputum) production; their use cannot be recommended until further evidence becomes available

The efficacy of drugs used in the treatment of cough has been evaluated in numerous studies including many systematic reviews.They show a lack of evidence for the effectiveness of nonprescription products in terms of reducing the frequency or severity of cough in children or adults. Some studies have shown benefit; however, the positive results in these studies were often of questionable clinical relevance.​^[Overall, there is little evidence for or against the effectiveness of nonprescription cough medicines. When counselling patients on selecting products, also consider the placebo effect, which can be significant.

Antihistamines

First-generation antihistamines (e.g., diphenhydramine) may have a small effect on cough caused by upper respiratory tract infections.​Their anticholinergic properties may reduce postnasal drip, which is one of the mechanisms responsible for cough in the common cold. The effect is modest and side effects such as drowsiness, dry mouth and confusion may outweigh potential benefit. Products containing antihistamines are no longer recommended for the treatment of acute cough until further evidence demonstrating efficacy becomes available.Second-generation antihistamines lack significant anticholinergic effects and therefore are not effective for acute cough unless secondary to allergic rhinitis (see Allergic Rhinitis).

Antitussives

Nonprescription antitussives act centrally to suppress cough.​ The exact mechanism is unknown; however, the brainstem is thought to be the main region where antitussive agents act to inhibit motor control of cough. Antitussives are not recommended when a cough performs a useful function. If used by a patient with a productive cough, more mucus is retained. ​

Dextromethorphan and codeine are commonly used to treat cough related to upper respiratory tract infections, although there is little evidence for efficacy.​ Some studies have shown that they are no more effective than placebo, while others demonstrated a modest benefit.​ Historically, dextromethorphan has been abused for its euphoric properties, while codeine carries a risk of dependence and addiction. Consequently, the American College of Chest Physicians (ACCP) 2006 guideline on the management of cough does not recommend centrally acting cough suppressants for cough secondary to upper respiratory tract infections. Conversely, codeine and dextromethorphan are effective for cough due to chronic obstructive pulmonary disease (COPD), suppressing cough counts by 40–60%,​ and may be used for short-term relief.

Expectorants

The protussive agents act peripherally. Guaifenesin is purported to enhance cough effectiveness by promoting the clearance of airway secretions. The efficacy and safety of guaiacol and ammonium chloride have not been established. Expectorants are reported to reduce sputum viscosity, permitting more effective removal of secretions from the respiratory tract.​ As with antitussives, there is a lack of evidence to support the efficacy of expectorants. They do not thin sputum nor increase sputum volume, even at doses higher than recommended.​ Adequate hydration with oral liquids and inhalation of humidified air is perhaps the best protussive or “expectorant” measure.

Other Agents

Honey may be an effective cough suppressant in children;​ no studies in adults are currently available. A Cochrane review concluded that honey administered before sleep is probably better than no treatment, placebo or diphenhydramine, and no different from dextromethorphan, at relieving cough symptoms. It is also probably better than placebo or salbutamol for reducing the duration of cough.​ Honey has demulcent, antioxidant and antibacterial effects. It is proposed that the demulcent effect may act to decrease cough. Because of the risk of botulism, give pasteurized honey only to immunocompetent children >1 year of age.

Zinc lozenges have been used to alleviate cough due to the common cold. Studies evaluating the efficacy of zinc in common cold symptoms have yielded conflicting results, and 2 meta-analyses have concluded there is insufficient evidence to recommend zinc preparations. In addition, zinc can be associated with unpleasant taste, mouth irritation and nausea.

Anesthetics such as benzocaine, phenol and menthol may reduce the sensitivity of peripheral nociceptors. They have been used as antitussives, but evidence for efficacy is poor.​ Rarely observed side effects include tingling or irritation at the site of administration and hypersensitivity reactions.

Inflammatory pathways have been largely investigated to play a role in the pathophysiology of cough; however, nonsteroidal anti-inflammatory drugs (NSAIDs) were found to have no effect on cough symptoms.​

Prescription Therapy

Bronchodilators such as salbutamol or formoterol are recommended only for cough due to obstructive lung disease such as asthma or COPD.​ Following a respiratory infection, patients sometimes develop a cough for which inhaled corticosteroids could be beneficial; the potential benefit of inhaled corticosteroids requires confirmation through further studies before making recommendations for their routine use.

For the treatment of cough secondary to another medical condition, see Allergic Rhinitis and Viral Rhinitis, Influenza, Sinusitis and Pharyngitis as well as Acute Bronchitis in the Compendium of Therapeutic Choices. For cough lasting >8 weeks, see Chronic Cough in Adults in the Compendium of Therapeutic Choices.

Cough in Special Populations

Children

For comparative ingredients of nonprescription products, consult the Compendium of Products for Minor Ailments—Baby Care Products: Cough and Cold.

Since 2008, Health Canada has required manufacturers to relabel nonprescription cough and cold medicines with certain active ingredients to indicate that they should not be used in children <6 years of age.​ Dextromethorphan, guaifenesin and first-generation antihistamines (including diphenhydramine) contained in cough and cold products are included in the list of active ingredients in the Health Canada advisory. See Viral Rhinitis, Influenza, Sinusitis and Pharyngitis, Table 3.

Although cough and cold medicines have been used by children for many years, little evidence supports their effectiveness in this population Furthermore, Health Canada has advised against the use of these products in children <6 years of age due to reports of very rare serious side effects as well as misuse and overdose. Rare but serious potential side effects include seizures, increased heart rate, decreased level of consciousness, abnormal heart rhythms and hallucinations

In children ≥6 years of age, dextromethorphan can be used to treat nonproductive cough, though evidence of efficacy in children is absent. Health Canada recommends that any cough and cold product containing codeine or other opioids (e.g., hydrocodone, normethadone) be avoided in children <18 years of age.​