Flopropione is a 5-HT receptor antagonist and also a catechol-o-methyltransferase (COMT) inhibitor^[1][2]. Flopropione also as an antispasmodic agent^[3]. IC50 & Target: 5-HT_1A receptor^[1], COMT^[2] In Vivo: The effect of Flopropione as an antispasmodic agent on the rate of passing a calculus from the urinary tract has been compared retrospectively with patients in whom passage was spontaneous. Flopropine has been shown, with statistical significance, to be superior to the control in cumulative passage rate after initiation of administration. Flopropine has been shown to exert a spasmolytic effect not only on smooth muscle of the gastrointestinal tract but also on smooth muscle of the pancreatobiliary and urinary systems^[3].