– 6-Hydroxy Buspirone, an active metabolite of the anxiolytic compound buspirone, is produced via the cytochrome P450 (CYP) isoform CYP3A4. This compound exhibits affinity for the serotonin (5-HT) receptor subtype 5-HT1A, demonstrating efficacy in the rat hippocampus and dorsal raphe with half-maximal effective concentrations (EC50s) of 4 and 1 µM, respectively. Furthermore, 6-Hydroxy Buspirone acts as a potent antagonist against dopamine D2, D3, and D4 receptors with half-maximal inhibitory concentrations (IC50s) of 3.1, 4.9, and 0.85 µM, respectively, and inhibits the organic cation transporters 1 (OCT1), OCT2, and OCT3 in S2 proximal tubule cells expressing human transporters, showcasing a concentration-dependent mechanism.