Definition

The besylate salt form of the R-enantiomer of azasetron, a benzamide derivative and selective serotonin (5-hydroxytryptamine; 5-HT) receptor and calcineurin antagonist, with potential antinauseant and antiemetic, and otoprotective activities. Upon administration, arazasetron selectively binds to and inhibits 5-HT subtype 3 receptors (5-HT3R) located peripherally on vagus nerve terminals and centrally in the chemoreceptor trigger zone (CTZ) of the area postrema, which may result in suppression of nausea and vomiting. R-azasetron also targets and inhibits the activation of calcineurin, thereby preventing inner ear lesions, nerve degeneration, induction of apoptosis and sensory hair loss. This may prevent hearing loss. Calcineurin activation plays a key role in structural degeneration, swelling, synaptic uncoupling and the induction of apoptosis in the inner ear leading to hair cell loss and hearing loss.