Spen

Generic composition: Risperidone

 General Description

Risperidone is a second-generation antipsychotic medication used in the treatment of a number of mood and mental health conditions including schizophrenia and bipolar disorder. It is one of the most widely used second generation antipsychotics.

Therapeutic group

• Atypical Anti-psychotics

 Dosage forms available

• Spen 1mg Tablets
• Spen 2mg Tablets
• Spen 3mg Tablets
• Spen 4mg Tablets

Uses

• Schizophrenia
• Bipolar Disorder
• Irritability associated with autistic disorder
• Monotherapy or in combination with lithium or valproate in acute mania phase of Bipolar Disorder

Dose

• Initial 2mg once or twice a day, increments of 1-2mg per day as tolerated to effective dose of 4-8mg per day

     *Dose reduction in hepatic impairment, renal impairment and in elderly

Side effect

Common side effects include movement problems, sleepiness, trouble seeing, constipation, and increased weight, orthostatic hypotension, tardive dyskinesia, neuroleptic malignant syndrome, an increased risk of suicide, and high blood sugar levels.

Contraindications

Hypersensitivity to risperidone or any other excipients

Mechanism of action

It has been proposed that the drug’s therapeutic activity in schizophrenia is mediated through a combination of dopamine Type 2 and serotonin Type 2 receptor antagonism. Dopamine receptor antagonism results in improvement of positive symptoms. Serotonin receptor antagonism provides relief from negative symptoms of schizophrenia.

Pharmacokinetics

Absorption: Rapidly absorbed after oral administration, food does not affect the rate or extent of absorption of risperidone, oral bioavailability is 70%, plasma protein binding is approximately 90%.

Distribution: Volume of distribution is approximately 1 to 2 L/kg.

Metabolism: Extensively metabolized by hepatic cytochrome P450 2D6 isozyme to 9-hydroxyrisperidone (paliperidone), which has approximately the same receptor binding affinity as risperidone.

Elimination: Extensively metabolized in liver and excreted via urine.

Half-life: 3 hours in extensive metabolizers and 20 hours in poor metabolisers,

 Drug interaction

• Carbamazepine and other enzyme inducers: may reduce plasma levels of risperidone
• SSRIs: may increase plasma levels of risperidone
• Anti-hypertensives

Precaution

• Patients on anti-hypertensives
• Elderly with dementia-related psychosis: increases risk of mortality
• Alcohol and other centrally acting drugs
• Patient taking Cimetidine and Ranitidine

References

• Drugbank
• Rxlist