Paliperidone is a dopamine antagonist of the atypical antipsychotic class of medications. It is developed by Janssen Pharmaceutica. Invega is an extended release formulation of paliperidone that uses the OROS extended release system to allow for once-daily dosing. Paliperidone palmitate is a long-acting injectable formulation of paliperidone palmitoyl ester indicated for once-monthly injection after an initial titration period. Paliperidone is used to treat mania and at lower doses as maintenance for bipolar disorder. It is also used for schizophrenia and schizoaffective disorder. Paliperidone is the primary active metabolite of the older antipsychotic risperidone. While its specific mechanism of action is unknown, it is believed paliperidone and risperidone act via similar, if not identical, pathways. Paliperidone has antagonist effect at α1 and α2 adrenergic receptors and at H1 histamine receptors.