Selective 5-HT1B receptor antagonist (pKi = 8.2). Displays > 60-fold selectivity over 5-HT1D, 5-HT1A, 5-HT1E, 5-HT1F, 5-HT2A and 5-HT2C receptors in radioligand binding and functional assays. Centrally active following oral administration in vivo.