Moreover, it has an affinity for serotonergic 5-HT2A and 5-HT2C, which may explain the very low does (6.25–37 mg) used in PD.145 It is, however, important to perform regular blood cell monitoring, as clozapine has a very low risk of severe neutropenia and agranulocytosis and a low risk of mild and moderate neutropenia.162 Nevertheless, clozapine is the most efficacious drug for the treatment of hallucinations and psychosis in PD and is likely underused in most countries.160. This evidence concerns the gene HTR2A and Parkinson disease.