OTCs Today
Daniel L. Krinsky, RPh, MS
Cough—a symptom of diverse infectious and noninfectious disorders that is classified as acute (<3 weeks), subacute (3–8 weeks), or chronic (>8 weeks)—is an important defensive respiratory reflex with potentially significant adverse physical and psychological consequences and economic impact. It is the most common symptom for which patients seek medical care.
Coughs are described as productive or nonproductive. Productive coughs expel secretions from the lower respiratory tract that, if retained, could impair ventilation and the lungs’ ability to resist infection. Nonproductive coughs, which are associated with viral and atypical bacterial infections, gastroesophageal reflux disease, cardiac disease, and some medications, serve no useful physiologic purpose.
Self-treatment and nonpharmacologic therapy
The goals of self-treatment are to reduce the number and severity of cough episodes and to prevent complications. Cough treatment is symptomatic; to stop the cough, one must treat the underlying disorder causing it. Medication selection for self-care depends on the nature and underlying cause of the cough.
Nonpharmacologic therapy includes use of nonmedicated lozenges, humidification, interventions to promote nasal drainage, and hydration. For most patients, carefully following product instructions and certain self-care measures will help ensure optimal therapeutic outcomes. Because babies and young children up to age 2 years cannot blow their noses, a rubber bulb nasal syringe may be used to clear the nasal passages to reduce cough caused by postnasal drip.
OTC pharmacologic options
Nonprescription pharmacologic therapy options include antitussives (suppressants) and protussives (expectorants). Antitussives control or eliminate cough and are the drugs of choice for nonproductive coughs. Protussives change the consistency of mucus and increase the volume of expectorated sputum. The most common nonprescription oral antitussives are dextromethorphan, diphenhydramine, and codeine. These are typically used “as needed”—within the limits of the maximum-recommended daily dose.
Dextromethorphan, diphenhydramine, and codeine act centrally in the medulla to increase the cough threshold. All are indicated for the suppression of nonproductive cough caused by chemical or mechanical respiratory tract irritation.
Dextromethorphan can be abused for its phencyclidine-like euphoric effect (“robotripping”). Abuse may be associated with psychosis and mania and is especially common among male adolescents. Adverse effects of diphenhydramine include those commonly associated with first-generation antihistamines, such as drowsiness, respiratory depression, blurred vision, urinary retention, dry mouth, and dry secretions.
At antitussive dosages, codeine is a Schedule V narcotic available without a prescription in 29 states and Washington, DC. Codeine-containing Schedule C–V products must contain no more than 200 mg of codeine per 100 mL. The most common adverse effects associated with antitussive codeine dosages are nausea, vomiting, sedation, dizziness, and constipation. This is not the first option for cough management in most patients.
Camphor and menthol are the only FDA-approved topical antitussives. Although their mechanism of action is not well described, inhaled camphor and menthol vapors stimulate sensory nerve endings within the nose and mucosa, creating a local anesthetic sensation and a sense of improved airflow. These agents may also suppress cough reflex sensitivity; however, objective evidence of antitussive efficacy is very limited.
Guaifenesin (glyceryl guaiacolate), the only FDA-approved expectorant, is indicated for symptomatic relief of acute, ineffective productive cough. Guaifenesin loosens and thins lower respiratory tract secretions, making minimally productive coughs more productive. However, data supporting its efficacy, especially at nonprescription dosages, are limited.
Considerations
While combinations of antitussives and protussives are readily available, promoted heavily, and popular with consumers, they are potentially counterproductive. Key exclusions include cough that worsens over 3 to 5 days, cough in children younger than 4 years, cough with a fever, and cough associated with a chronic illness such as congestive heart failure or COPD. In 2008, manufacturers voluntarily updated labels for cough and cold products to state “do not use” in children younger than 4 years.