Risperidone

Risperidone is an atypical antipsychotic agent that displays SR-2A inhibition. Risperidone also displays high inhibition of D2DR (Ki values are 0.4 and 3.13 nM for 5-SR-2A and D2DR receptors respectively).

Comparative study of clozapine versus risperidone in treatment-naive, first-episode schizophrenia: A pilot study.[Pubmed:28361822]

Indian J Med Res. 2016 Nov;144(5):697-703.

BACKGROUND & OBJECTIVES: Clozapine may be more useful in treatment-naive patients with first-episode schizophrenia for better symptoms control and improving quality of life. The current study was carried out to compare the efficacy and tolerability of clozapine versus Risperidone in treatment-naive, first-episode patients of schizophrenia. METHODS: This was a comparative, open-label, six months prospective study of treatment-naive, first-episode patients with schizophrenia between the age group of 18 and 40 yr diagnosed as per the International Classification of Diseases-10 (ICD-10) criteria. A total of 63 patients were recruited and randomly assigned to clozapine group or Risperidone group using computer-generated random number tables. Eight patients were lost to follow up. The dosages of the respective drugs were kept in therapeutic range of 200-600 mg/day and 4-8 mg/day orally for clozapine and Risperidone, respectively. RESULTS: On general psychopathology score, after six months of intervention, clozapine led to 60.32 per cent mean reduction in Positive and Negative Syndrome Scale (PANSS) for Schizophrenia total score while Risperidone led to 56.35 per cent mean reduction in PANSS total score, which meant more improvement with clozapine. Clozapine group was found to have significant improvement in quality of life (P = 0.04339). On Glasgow Antipsychotic Side-effect Scale, clozapine was superior to Risperidone. The most common side effects observed in clozapine group were oversedation (78.96%) and dizziness (55.23%), and in Risperidone group, common side effects were rigidity (62.36%), sedation (38.69%), tremors (65.69%) and menstrual irregularities in 80.25 per cent of female patients. INTERPRETATION & CONCLUSIONS: The findings of this preliminary study showed clozapine as a better choice than Risperidone in terms of efficacy, tolerability and better quality of life in treatment-naive, first-episode schizophrenia. However, further studies need to be done on a larger group of patients to confirm the findings.

Long-acting Injectable Risperidone Use in an 11-Years-Old Bipolar Child.[Pubmed:28360814]

Noro Psikiyatr Ars. 2016 Dec;53(4):361-363.

Early-onset bipolar disorder is difficult for child psychiatrists in terms of both diagnosis and treatment. The proper diagnostic evaluation is negatively impacted by the atypical clinical manifestation and rapid cycling pattern of the disease, together with common comorbidity with attention-deficit hyperactivity disorder and anxiety disorder. In addition to poor insight, nonadherence to treatment, poor family coping skills, and insufficient child psychiatric inpatient units make clinicians unsuccessful in following up and treating such patients. Risperidone is a commonly used atypical antipsychotic it has been approved for the treatment of manic and mixed episodes of bipolar disorder even in 10-17-year-old patients, and it is commonly used. It has a long-acting injectable formulation. Studies on its long-acting form in younger children are limited. In this case presentation, the diagnostic procedure in an 11-year old child with bipolar disorder will be presented. Long-acting injectable Risperidone use in the case of nonadherence to treatment and observed side effects will be discussed.

Risperidone: a novel antipsychotic with balanced serotonin-dopamine antagonism, receptor occupancy profile, and pharmacologic activity.[Pubmed:7520908]

J Clin Psychiatry. 1994 May;55 Suppl:5-12.

The interaction of Risperidone, 9-hydroxyRisperidone (the principal active metabolite), and clozapine with neurotransmitter receptors was investigated in vitro using animal brain tissue homogenates and cloned human receptors expressed in cells and ex vivo using quantitative receptor autoradiography in rat and guinea pig brain sections. In vitro, Risperidone and 9-hydroxyRisperidone had similar binding profiles, and their highest affinity was for 5-HT2A receptors (cloned human, Ki 0.4 nM); affinities for other 5-HT-receptor subtypes were at least 100 times lower. Risperidone bound to 5-HT2A receptors with 20 times greater affinity than clozapine and 170 times greater affinity than haloperidol. Clozapine primarily bound to histamine H1 receptors and haloperidol to dopamine D2 receptors. The binding affinity of Risperidone and 9-hydroxyRisperidone for the D2 family of receptors (D2L, D2S, D3, D4) was one order of magnitude lower than their affinity for 5-HT2A receptors. Risperidone bound to D2 and D3 receptors with 50 and 20 times greater affinity than clozapine and was only 2 to 3 times less potent than haloperidol. All compounds bound with similar affinities to D4 receptors (Ki 5-9 nM), and their affinities for D1 receptors were 100 times lower than for D4 receptors. The ex vivo receptor occupancy profile of the compounds matched the in vitro receptor binding profile. A conspicuous property of Risperidone, not seen for the other compounds, was the shallow occupancy curve at D2 receptors in the striatum and mesolimbic brain area. Moreover, it was observed that antagonism of strong D2-receptor stimulation by apomorphine in rats was achieved at less than 50% D2 occupancy by the antipsychotics.(ABSTRACT TRUNCATED AT 250 WORDS)

Biochemical profile of risperidone, a new antipsychotic.[Pubmed:2460616]

J Pharmacol Exp Ther. 1988 Nov;247(2):661-70.

Risperidone was compared to the 5-hydroxytryptamine2 antagonist ritanserin and to the dopamine-D2 antagonist haloperidol. The in vitro receptor binding (neurotransmitter-, peptide- and ion channel binding sites) and neurotransmitter uptake profile were investigated. Risperidone revealed, like ritanserin, a very high binding affinity for 5-hydroxytryptamine2 receptors (Ki = 0.16 and 0.30 nM, respectively) and a slow dissociation (half-time, 31 and 160 min). In accordance, Risperidone (IC50 = 0.5 nM) and ritanserin (IC50 = 1.8 nM) potently blocked serotonin-induced 32P-phosphatidic acid formation in human blood platelets. Risperidone showed, like haloperidol, high binding affinity for dopamine-D2 receptors (Ki = 3.13 and 1.55 nM, respectively) and rapid dissociation (half-time, 2.7 and 5.8 min). Risperidone displayed higher binding affinity than ritanserin and haloperidol for alpha-1 adrenergic (Ki = 0.8 nM), histamine-H1 (Ki = 2.23 nM) and alpha-2 adrenergic receptors (Ki = 7.54 nM). In in vitro superfusion experiments, Risperidone and haloperidol reversed at nanomolar concentrations the inhibition by LY 171555 (a dopamine-D2 agonist) and by amphetamine of potassium and electrically evoked release of [3H]acetylcholine from striatal slices (postsynaptic dopamine-D2 effects). Both drugs reversed with similar potency the inhibition by LY 171555 of electrically evoked release of [3H]dopamine (a presynaptic dopamine-D2 effect). Risperidone did not affect the activation by amphetamine of [3H]dopamine efflux from rat striatal slices. Risperidone enhanced at nanomolar concentrations the stimulated [3H]norepinephrine efflux from cortical slices and it similarly reversed the inhibition by clonidine, at concentrations corresponding to its binding affinity for alpha-2 adrenergic receptors. The in vitro biochemical properties of Risperidone are in agreement with the reported in vivo pharmacological profile, the relation to clinical findings is discussed.

Risperidone is a serotonin 5-HT2 receptor blocker, P-Glycoprotein inhibitor and potent dopamine D2 receptor antagonist, with Kis of 4.8, 5.9 nM for 5-HT2A and dopamine D2 receptor, respectively.

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