One of the following drug causes least gain in weight

(B) Ziprasidone # Risperidone, a benzisoxazole derivative, is more potent at 5HT2 than D2 receptor sites, like clozapine, but it also exerts significant a2 antagonism, a property that may contribute to its perceived ability to improve mood and increase motor activity.> Risperidone is not as effective as clozapine in treatment resistant cases but does not carry a risk of blood dyscrasias.> Olanzapine is similar neurochemically to clozapine but has a significant risk of inducing weight gain.> Quetiapine is distinct in having a weak D2 effect but potent a1 and histamine blockade.> Ziprasidone causes minimal weight gain and is unlikely to increase prolactin, but may increase QT prolongation.> Aripiprazole also has little risk of weight gain or prolactin increase but may increase anxiety, nausea, and insomnia as a result of its partial agonist properties.ANTIPSYCHOTIC AGENTSNameUsualPOSide Effects Daily Dose, mgSedationCommentsClozapine(Clozaril)2 0 0 - 600Agranulocytosis (1%); weight gain; seizures; drooling; hyperthermia+ +Requires weekly WBCRisperidone (Risperdal) observed with doses >6 mg qd2-6Orthostasis+Requires slow titration; EPSEsOlanzapine(Zyprexa)10-20Weight gain+ +Mild prolactin elevationQuetiapine(Seroquel)3 5 0 - 700Sedation; weight gain; anxiety+ + +Bid dosingZiprasidone(Geodon)40-60Orthostatic hypotension+/+ +Minimal weight gain; increases QT intervalAripiprazole (Ability)10-30Nausea, anxiety, insomnia0/+Mixed agonist /antagonist