Paliperidone palmitate-d4 (9-Hydroxyrisperidone palmitate-d4) is the deuterium labeled Paliperidone palmitate (HY-A0019A). Paliperidone palmitate is an orally effective competitive antagonist of dopamine D2 receptors and 5-hydroxytryptamine 2A (5-HT2A) receptors that can cross the blood-brain barrier. Paliperidone palmitate competitively inhibits the effects of dopamine and 5-hydroxytryptamine by binding to dopamine D2 receptors and 5-HT2A receptors, regulating the balance of the neurotransmitter system and thus exerting antipsychotic activity. Paliperidone palmitate is mainly used in the research field of schizophrenia[1][2][3].