It has no serious adverse effects, but there is no clear evidence of its efficacy. Their efficacy is doubtful, particularly in the dosages of most preparations. In some patients, mucolytics may aggravate airway obstruction by causing bronchospasm. They seem to offer no advantage over mucolytics. Local irritation of the buccal and pharyngeal mucosa and allergic reactions commonly follow repeated doses.
Antihistamines have little or no use in treating cough.
Their drying action on the respiratory mucosa may be helpful in the early congestive phase of acute coryza but may be deleterious, especially to patients with a nonproductive cough resulting from retained viscous airway secretions. They may also be beneficial in chronic cough due to postnasal drip associated with allergic sinusitis. Atropine is undesirable because it thickens bronchial secretions. The anticholinergic drug ipratropium bromide can often ameliorate an irritating type of cough and does not adversely affect mucus secretions. Inhaled corticosteroids have become a mainstay in the treatment of cough in asthma.