Flopropione is a 5-HT receptor antagonist and also a catechol-o-methyltransferase (COMT) inhibitor[1][2]. Flopropione also as an antispasmodic agent[3].

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].

References:
[1]. Burns SM, et al. High-throughput luminescent reporter of insulin secretion for discovering regulators of pancreatic Beta-cell function. Cell Metab. 2015 Jan 6;21(1):126-37.
[2]. C Barlow, et al. Modulation of neurogenesis using d-cycloserine combinations. 2010-08-26. PAT - US2010216805.
[3]. Ohgaki K, et al. Facilitation of expulsion of ureteral stones by addition of α1-blockers to conservative therapy. Scand J Urol Nephrol. 2010 Dec;44(6):420-4.