Specific antitussives

The physiologic mechanism of cough is complex, and little is known about the specific mechanism of action of the opioid antitussive drugs. It appears likely that both central and peripheral effects play a role. 

Black cohosh is said to possess antirheumatic, antitussive, sedative, and emmenagogue properties. It is used for intercostals myalgia, sciatica, whooping cough, chorea, tinnitus, dysmenorrheal, uterine colic, and specifically for muscular rheumatism and rheumatoid arthritis. 

Thyme is reputed to possess carminative, antispasmodic, antitussive, expectorant, secretomotor, bactericidal, anthelmintic, and astringent properties. Traditionally, it is used for dyspepsia, chronic gastritis, asthma, diarrhea and enuresis in children, laryngitis, tonsillitis (as a gargle), and specifically for pertussis and bronchitis. 

Kamei J, Tanihara H, Kasuya Y (1990) Antitussive effects of two specific kappa-opioid agonists, U-50,488H and U-62,066E, in rats, Eur J Pharmacol 187 281-286 Kamei J, Iwamoto Y, Misawa M, Kasuya Y (1993) Effects of rimcazole, a specific antagonist of sigma sites, on the antitussive effects of non-narcotic antitussive drugs, Eur J Pharmacol... 

The pharmacology of centrally active antitussive drugs is a multifactorial topic that involves not only pharmacological and pharmacokinetic issues but neurophysiology as well. This review will focus on three primary matters related to the brainstem actions of these drugs (1) location of action, (2) identity of neurones affected by the drugs, (3) receptor specificity. There are other informative reviews available (Reynolds et al. 2004). 

Studies to identify the receptor specificity of antitussive drugs have been restricted to animal models. In humans, investigations of the effects of antitussive drugs are usually focused on demonstrating efficacy. Studies in animal models usually involve the use of specific agonists and/or antagonists to demonstrate receptor specificity. 

Sedating antihistamines such as diphenhydramine are used in many cough medicines and the efQcacy of these medicines as antitussives may be due to their general sedative effects rather than any specific interaction with pharmacological receptors. 

This chapter will discuss the treatment approaches to acute and chronic cough, highlight the currently available disease-specific and symptomatic cough suppressants, and look into the development of more efficacious antitussives, particularly for chronic cough. The treatment of chronic cough has two aims specific treatments of causative factors (disease-specific), and symptomatic cough suppression. 

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