Malabar Nut Tree (Justicia adhatoda), also known as Vasaka, has been traditionally used in Ayurvedic and Unani medicine for the management of respiratory ailments, particularly cough. The leaf extract contains several bioactive alkaloids, most notably vasicine and vasicinone, which exhibit bronchodilatory, expectorant, and antitussive (cough-suppressing) properties. Several preclinical studies and a limited number of clinical trials have investigated its effects on cough and other respiratory symptoms.

Experimental studies in animals demonstrate that vasicine exerts significant antitussive activity, comparable to standard cough suppressants, and also helps in thinning bronchial secretions, which can be beneficial in both productive and dry coughs. Human studies, though fewer in number and often of modest methodological quality, suggest that formulations containing Malabar Nut extract can reduce cough frequency and severity, particularly in acute and chronic bronchitis. The World Health Organization acknowledges the traditional use of Justicia adhatoda leaves for cough and asthma, and several pharmacopoeias list it as an ingredient in herbal cough remedies.

While the bulk of evidence comes from laboratory and traditional use data, and high-quality randomized controlled trials are limited, the presence of biologically active compounds with demonstrated pharmacological effects offers scientific validation for its use as a supportive treatment for cough, including dry cough.