Asenapine is an antipsychotic drug. The mechanism of action of asenapine, as with other drugs having efficacy in schizophrenia and bipolar disorder, is unknown. Asenapine exhibits high affinity for serotonin 5-HT1A, 5-HT1B, 5-HT2A, 5-HT2B, 5-HT2C, 5-HT5, 5-HT6, and 5-HT7 receptors, dopamine D2, D3, D4, and D1 receptors, α1 and α2-adrenergic receptors, and histamine H1 receptors, and moderate affinity for H2 receptors. In in vitro assays asenapine acts as an antagonist at these receptors. It has been suggested that the efficacy of asenapine in schizophrenia is mediated through a combination of antagonist activity at D2 and 5-HT2A receptors. Asenapine is approved by the FDA for the acute treatment of schizophrenia in adults and for the acute treatment of manic or mixed episodes associated with bipolar I disorder, with or without psychotic features, in adults.