Piperidin-4YL-pyridazin-3-ylamine derivatives as fast dissociating dopamine 2 receptor antagonists

A method of treating a patient with psychosis comprising administering to said patient a therapeutically effective amount to treat psychosis of a compound of formula (I)

• or a pharmaceutically acceptable salt, hydrate or solvate thereof, or a stereoisomeric form thereof, wherein
• R is hydrogen;
• R1 is phenyl;
• phenyl substituted with 1, 2 or 3 substituents each independently selected from the group consisting of hydrogen, halo, cyano,
• C1-4alkyl, C1-4alkyloxy, perfluoroC1-4alkyl, diC1-4alkylamino;
• thienyl;
• thienyl substituted with 1 or 2 substituents selected from the group consisting of halo and C1-4alkyl;
• C3-8cycloalkyl;
• or C5-7cycloalkenyl;
• R2 is hydrogen or C1-6alkyl;
• R3 is trifluoromethyl;
• and
• R4 and R5 are hydrogen.