Risperidone; Uses, Dosage, Side Effects, Interactions

Risperidone








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Risperidone is a benzisoxazole derivative with the antipsychotic property. Risperidone selectively antagonizes serotonin (5-HT) effects via the cortical 5-HT2 receptor, and, to a lesser extent, competes with dopamine at the limbic dopamine D2 receptor. The antagonism leads to decreased psychotic effects, such as hallucinations and delusions. In addition, risperidone has low to moderate affinity for histamine H1, 5-HT1A, 5-HT1C, and 5-HT1D receptors, while it has weak affinity for dopamine D1 and haloperidol-sensitive sigma site receptors.

Risperidone is an antipsychotic medication & it is mainly used to treat schizophrenia, bipolar disorder, and irritability in people with autism. Schizophrenia and various mood disorders are thought to be caused by an excess of dopaminergic D2 and serotonergic 5-HT2A activity, resulting in overactivity of central mesolimbic pathways and mesocortical pathways, respectively. Risperidone inhibits dopaminergic D2 receptors and serotonergic 5-HT2A receptors in the brain. It is also said to block histamine receptors and other neural receptors which are currently being studied.

Mechanism of Action of Risperidone

Though its mechanism of action is not fully understood at this time, the current focus is on the ability of risperidone to inhibit the D2 dopaminergic receptors and 5-HT2A serotonergic receptors in the brain. Schizophrenia is thought to be caused by an excess of dopaminergic D2 and serotonergic 5-HT2A activity, resulting in overactivity of central mesolimbic pathways and mesocortical pathways, respectively.

D2 dopaminergic receptors are transiently inhibited by risperidone, reducing dopaminergic neurotransmission, therefore decreasing positive symptoms of schizophrenia, such as delusions and hallucinations. Risperidone binds transiently and with loose affinity to the dopaminergic D2 receptor, with an ideal receptor occupancy of 60-70% for optimal effect. Rapid dissociation of risperidone from the D2 receptors contributes to the decreased risk of extrapyramidal symptoms (EPS), which occur with permanent and high occupancy blockade of D2 dopaminergic receptors. Low-affinity binding and rapid dissociation from the D2 receptor distinguish risperidone from the traditional antipsychotic drugs. A higher occupancy rate of D2 receptors is said to increase the risk of extrapyramidal symptoms and is, therefore, to be avoided.

Risperidone is an atypical antipsychotic drug that is widely prescribed for young patients with different psychotic disorders. The long-term effects of this antipsychotic agent on neuronal receptors in developing brain remain unclear and require further investigation. In this study, we examined the effects of long-term treatment of risperidone on two serotonin receptor subtypes in brain regions of juvenile rat. Levels of 5-HT(1A) and 5-HT(2A) receptors in forebrain regions of juvenile rats were quantified after 3 weeks of treatment with three different doses of risperidone (0.3, 1.0 and 3.0mg/kg). Findings were compared to previously reported changes in 5-receptors after risperidone treatment (3.0mg/kg) in the adult rat brain. The three doses of risperidone selectively and dose-dependently increased levels of 5-HT(1A) receptors in medial-prefrontal and dorsolateral-frontal cortices of juvenile animals. The higher doses (1.0 and 3.0mg/kg) of risperidone also increased 5-HT(1A) receptor binding in hippocampal CA(1) region of juvenile but not adult rats. In contrast, the three doses of risperidone significantly reduced 5-HT(2A) labeling in medial-prefrontal and dorsolateral-frontal cortices in juvenile as well as in adult animals in an equipotent fashion. 5-HT(1A) and 5-HT(2A) receptors in other forebrain regions were not altered by repeated risperidone treatment. These findings indicate that there are differential effects of risperidone on 5-HT(1A) and 5-HT(2A) receptors in juvenile animals and that the 5-HT system in developing animals is more sensitive than adults to the long-term effects of risperidone

Indications of Risperidone

Contra-Indications of Risperidone

Dosage of Risperidone

Strengths: 0.25 mg; 0.5 mg; 1 mg; 2 mg; 3 mg; 4 mg; 25 mg/2 weeks; 37.5 mg/2,

Schizophrenia

Oral Formulations

  • Initial dose: 2 mg orally per day
  • Titration dose: May increase in increments of 1 to 2 mg per day at the interval of 24 hours or more, as tolerated.
  • Maintenance dose: 2 to 8 mg orally per day
  • Maximum dose: 16 mg orally per day

Long-acting IM Injection

  • Initial dose: 25 mg IM every 2 weeks
  • Titration dose: May increase to 37.5 mg or 50 mg if needed; dose titration should occur no more frequently than every 4 weeks as expected drug release starts 3 weeks after injection.
  • Maximum dose: 50 mg IM every 2 weeks

 Bipolar Disorder

Oral Formulations

  • Initial dose: 2 to 3 mg orally per day
  • Titration dose: May increase in increments of 1 mg per day at the interval of 24 hours or more, as tolerated.
  • Maximum dose: 6 mg orally per day

Long-acting IM Injection

  • Initial dose: 25 mg IM every 2 week
  • Titration dose: May increase to 37.5 mg or 50 mg if needed; dose titration should occur no more frequently than every 4 weeks as expected drug release starts 3 weeks after injection.
  • Maximum dose: 50 mg IM every 2 weeks

Pediatric Schizophrenia

13 years or older

  • Initial dose: 0.5 mg orally once a day
  • Titration dose: May increase in increments of 0.5 mg to 1 mg per day at the interval of 24 hours or more, as tolerated.
  • Maintenance dose: 3 mg orally per day
  • Maximum dose: 6 mg orally per day

Pediatric  Bipolar Disorder

10 years or older

  • Initial dose: 0.5 mg orally once a day
  • Titration dose: May increase in increments of 0.5 mg to 1 mg per day at the interval of 24 hours or more, as tolerated.
  • Maximum dose: 6 mg orally per day

Pediatric Autism

5 to 17 years Greater than 15 kg and less than 20 kg

  • Initial dose: 0.25 mg orally once a day
  • Titration: after a minimum of 4 days, may increase to 0.5 mg per day; maintain this dose for a minimum of 14 days; subsequent dose increases may be made in increments of 0.25 mg at intervals of 2 weeks or more, as tolerated.
  • Maintenance dose: Once sufficient clinical response has been achieved and maintained, healthcare providers should consider gradually reducing the dose to achieve the optimal balance of safety and efficacy.

20 kg or greater

  • Initial dose: 0.5 mg orally once a day
  • Titration: After a minimum of 4 days, may increase to 1 mg per day; maintain this dose for a minimum of 14 days; subsequent dose increases in increments of 0.5 mg at intervals of 2 weeks or more, as tolerated.
  • Maintenance dose: Once sufficient clinical response has been achieved and maintained, healthcare providers should consider gradually reducing the dose to achieve the optimal balance of safety and efficacy.

Side Effects of Risperidone

The most common

More common

Rare

Drug Interactions

Risperidone may interact with the following drug, supplements, & may change the efficacy of the drug

Pregnancy Catagory of Risperidone

FDA Pregnancy Category C

Pregnancy

The safety of risperidone for use during pregnancy has not been established. Risperidone should not be used during pregnancy unless the expected benefits outweigh the potential risks. If you become pregnant while taking risperidone, contact your doctor immediately.

Lactation

Risperidone passes into breast milk. Women should not breast-feed while taking risperidone. The safety and effectiveness of risperidone have not been established for use by children and adolescents under 18 years of age.

References

Risperidone

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