Meprotixol is a thiaxanthene derivative. Meprotixol revealed a potent antitussive activity. It has slight central depressive effect. Meprotixol reduces the spontaneous motor activity of mice, but its potency is negligible in comparison with those of neuroleptics such as chlorpromazine and chlorprothixene. Meprotixol in suitable doses reduces the quantity of barbiturate required to secure anesthesia. Meprotixol showed a potent broncho-spasmolytic effect against 5-hydroxytryptamine spasms in guinea pigs. This compound has a marked inhibitory effect against various forms of edema and exudation in the granuloma pouch, though the inhibition of granuloma formation was only slight. Phenylbutazone seemed to be more effective than meprotixol in the treatment of rheumatic disease.