HTR1A and Anxiety: Indeed, IR formulation, even when administered at low doses (30 mg), has been demonstrated to primarily recruit 5-HT1A, 5-HT1D, 5-HT2A, and 5-HT2B serotonergic receptors and α1A, α1B, and α1D adrenergic receptors, thus explaining the clinically observed efficacy of trazodone IR in treating insomnia and anxiety.