dextromethorphan and moguisteine

Chronic cough is a common symptom but only a fraction of patients seek medical attention. Addressing the causes of chronic cough may lead to control of cough; however, this approach is not always successful since there is a certain degree of failure even when the cause(s) of cough are adequately treated; in idiopathic cough, there is no cause to treat. Persistent cough may be associated with deterioration of quality of life, and treatment with cough suppressants is indicated. Currently available cough suppressants include the centrally acting opioids such as morphine, codeine, and dextromethorphan. Peripherally acting antitussives include moguisteine and levodropropizine. Early studies report success in reducing cough in patients with chronic bronchitis or COPD; however, a carefully conducted study showed no effect of codeine on cough of COPD. Success with these cough suppressants can be achieved at high doses that are associated with side effects. Slow-release morphine has been reported to be useful in controlling intractable cough with good tolerance to constipation and drowsiness. There have been case reports of the success of centrally acting drugs such as amitryptiline, paroxetine, gabapentin, and carbamezepine in chronic cough. New opioids such as nociceptin or antagonists of TRPV1 may turn out to be more effective. Efficacy of cough suppressants must be tested in double-blind randomised trials using validated measures of cough in patients with chronic cough not responding to specific treatments. Patients with chronic cough are in desperate need of effective antitussives that can be used either on demand or on a long-term basis.

Topics: Antitussive Agents; Central Nervous System; Chronic Disease; Codeine; Cough; Dextromethorphan; Humans; Morphine; Narcotics; Reflex; Thiazolidines; Treatment Outcome

The synthesis of a novel class of antitussive agents is described. The compounds were examined for antitussive activity in guinea pig after cough induction by electrical or chemical stimulation. Ethyl 2-[(2-methoxyphenoxy)methyl]-beta-oxothiazolidine-3-propanoate (BBR 2173, moguisteine, 7) and other structurally related compounds showed a significant level of activity, comparable to that of codeine and dextromethorphan. The compounds presented in this paper are characterized by the N-acyl-2-substituted-1,3-thiazolidine moiety, which is a novel entry in the field of antitussive agents. The serendipitous discovery of the role played by the thiazolidine moiety in determining the antitussive effect promoted extensive investigations on these structures. This optimization process on N-acyl-2-substituted-1,3-thiazolidines led to the initial identification of 2-[(2-methoxypheoxy)methyl]-3-[2-(acetylthio)acetyl]- 1,3-thiazolidine (18a) as an interesting lead compound. The careful study of the rapid and very complicated metabolism of 18a provided further insights for the design of newer related derivatives. The observation that the metabolic oxidation on the lateral chain's sulfur of 18a to sulfoxide maintained the antitussive properties suggested the introduction of isosteric functional groups with respect to the sulfoxide moiety. Subsequent structural modifications showed that hydrolyzable malonic residues in the 3-position of the thiazolidine ring were able to assure high antitussive activity. This optimization ultimately led to the selection of moguisteine (7) as the most effective and safest representative of the series. Moguisteine is completely devoid of unwanted side effects (such as sedation and addiction), and its activity was demonstrated also in clinical studies.

Topics: Animals; Antitussive Agents; Drug Design; Guinea Pigs; Male; Rats; Thiazoles; Thiazolidines