Antitussive effects of ethyl acetate fraction of Terminalia chebula on sulphur dioxide (SO2) gas induced cough have been examined in mice. Safety profile of Terminalia chebula was established by determining LD50 and acute neurotoxicity. The result showed that extract of Terminalia chebula dose dependently suppressed SO2 gas induced cough in mice. Terminalia chebula, after i.p. administration at dose level 500？mg/kg, offered maximum cough suppressive effects; that is, number of coughs at 60？min was (mean ± SEM) as compared to codeine 10？mg/kg; i.p., dextromethorphan 10？mg/kg; i.p., and saline, having frequency of cough , , and , respectively. LD50 value of Terminalia chebula was approximately 1265？mg/kg, respectively. No sign of neural impairment was observed at antitussive doses of extract. Antitussive effect of Terminalia chebula was partly reversed with treatment by naloxone (3？mg/kg; s.c.) while rimcazole (3？mg/kg; s.c.) did not antagonize its cough suppression activity. This may suggest that opioid receptors partially contribute in antitussive action of Terminalia chebula. Along with this, the possibility of presence of single or multiple mechanisms activated by several different pharmacological actions (mainly anti-inflammatory, antioxidant, spasmolytic, antibacterial, and antiphlegmatic) could not be eliminated. 1. Introduction Plants have formed the basis of sophisticated traditional medicine systems that have been in existence for thousands of years [1]. Ayurvedic, Unani, Kampo, and traditional Chinese medicine based systems continue to play an essential role in primary health care [2]. It has been estimated by World Health Organization (WHO) that approximately 80% of world’s inhabitants, mainly residing in developing countries, rely on traditional medicine, and 85% of traditional medicine involves the use of plant extracts or their active principles. The plant-derived products also play a significant role in health care system of the remaining 20% population, mainly residing in developed countries. In the USA, for example, 25% of all prescriptions dispensed from community pharmacies from 1959 to 1980 contained plant extracts or active principles prepared from higher plants [3]. Most popular cough medicines throughout the world are based on herbal derivatives. The number of plants that have been accepted as antitussives by different societies is immense. For example, the USA Physician Desk Reference (PDR) for Herbal Medicine categorizes over 100 herbs as antitussives [4]. Opium, Ammi, coltsfoot, plantain ma huang, thyme, and so forth are used
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