Risperidone

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Risperidone is an atypical antipsychotic. It is mainly used to treat schizophrenia, manic or mixed episodes associated with Bipolar I Disorder and irritability in people with autism

Contents

[edit] BRAND NAMES

[edit] STRUCTURE

Risperidone.jpg

[edit] MECHANISM OF ACTION

Risperidone is an antipsychotic drug belonging to the class of atypical antipsychotics (Second generation antipsychotics). Other atypical antipsychotic drugs include Quetiapine, Paliperidone, Olanzapine, Aripiprazole, Clozapine, Ziprasidone and Amisulpride.

Atypical antipsychotics have become an increasingly popular alternative to typical antipsychotics (First generation antipsychotics) like haloperidol because they are less likely to cause extra-pyrammidal side-effects (EPS), drug induced involuntary movements, than are the older drugs.

Risperidone interact with a broad range of neurotransmitter receptors. Its efficacy in Schizophrenia is mediated through a combination of antagonism at dopamine D2 receptors in the mesolimbic pathway and serotonin 5HT2A receptors in the frontal cortex. Antagonism at D2 receptors relieves positive symptoms while antagonism at 5HT2A receptors relieves negative symptoms of schizophrenia.
At low doses, the greater selectivity at 5HT2a receptors than for D2 receptors explains the relatively low frequency of extrapyramidal side effects.

Risperidone acts also as an α1 and α2 adrenergic antagonist, and H1 histaminergic receptors antagonist.

[edit] INDICATIONS

FDA Approved:

  • Treatment of schizophrenia in adults and adolescents aged 13-17 years. Schizophrenia is a mental illness that has a number of symptoms, including disorganised thinking and speech, hallucinations (hearing or seeing things that are not there), suspiciousness and delusions (mistaken beliefs)
  • Short-term treatment of acute manic or mixed episodes associated with Bipolar I Disorder in adults, Alone, or in combination with lithium carbonate or valproate
  • Alone, for the short-term treatment of acute manic or mixed episodes associated with Bipolar I Disorder in children and adolescents aged 10-17 years
  • Treatment of irritability associated with autistic disorder in children and adolescents aged 5-16 years

[edit] DOSAGE

Adults:

  • Schizophrenia: Starting dose: 2 mg/day; Target dose: 4-8 mg/day within several days (increase 1-2 mg daily).
  • Bipolar disorder: Starting dose: 2-3 mg/day; Target dose: 1-6 mg/day within several days (increase 1 mg daily).


Adolescents aged 13-17 years:

  • Schizophrenia: Starting dose: 0,5 mg/day; Target dose: 3 mg/day within several days (increase 0,5-1 mg daily).


Adolescents aged 10-17 years:

  • Bipolar I Disorder: Starting dose: 0,5 mg/day; Target dose: 2,5 mg/day within several days (increase 0,5-1 mg daily).


  • Irritability associated with autistic disorder in children and adolescents aged 5-16 years: Starting dose: 0,25 mg/day (<20 kg) and 0.5 mg /day (≥20 kg); Target dose: 0,5 mg/day (<20 kg) and 1 mg /day (≥20 kg) .Increase 0,25-0,50 mg every at least 14 days).

[edit] CONTRAINDICATIONS

Known hypersensitivity to Risperidone

[edit] WARNINGS AND PRECAUTIONS

  • Elderly Patients with Dementia-Related Psychosis: Risperidone is not approved for the treatment of dementia-related psychosis and/or behavioural disturbances and is not recommended for use in this particular group of patients because of an increase in mortality and the risk of cerebrovascular adverse events (e.g., stroke, transient ischemic attack).
  • Neuroleptic Malignant Syndrome: Manage with immediate discontinuation and close monitoring. NMS is a rare but potentially life-threatening condition associated with antipsychotic medicinal products. Rare cases reported as NMS have also been received in association with Risperidone. Clinical manifestations of NMS are hyperpyrexia (extreme elevation of body temperature), muscle rigidity, altered mental status, and evidence of autonomic instability (irregular pulse or blood pressure, tachycardia, diaphoresis, and cardiac dysrhythmia). Additional signs may include elevated creatine phosphokinase, myoglobinuria (rhabdomyolysis), and acute renal failure. If a patient develops signs and symptoms indicative of NMS, or presents with unexplained high fever without additional clinical manifestations of NMS, all antipsychotic medicines, including Risperidone must be discontinued.
  • Tardive Dyskinesia (A syndrome of potentially irreversible involuntary movements, especially of the lower face): Discontinue if clinically appropriate.
  • Hyperglycemia: In some cases extreme and associated with ketoacidosis or hyperosmolar coma or death, has been reported in patients taking Risperidone . Patients taking Risperidone should be monitored for symptoms of hyperglycemia and undergo fasting blood glucose testing at the beginning of, and periodically during, treatment.
  • Hyperprolactinemia: As with other drugs that antagonize dopamine D2 receptors, Risperidone elevates prolactin levels. Galactorrhea, amenorrhea, gynecomastia, and impotence have been reported in patients receiving prolactin-elevating compounds. Longstanding hyperprolactinemia when associated with hypogonadism may lead to decreased bone density in both female and male subjects. Tissue culture experiments indicate that approximately one-third of human breast cancers are prolactin dependent in vitro, a factor of potential importance if the prescription of these drugs is contemplated in a patient with previously detected breast cancer
  • Orthostatic Hypotension: Orthostatic hypotension associated with dizziness, tachycardia, bradycardia and, in some patients, syncope, may occur especially during initial dose titration. Use caution in patients with cardiovascular disease, cerebrovascular disease, and those conditions that could affect hemodynamic responses.
  • Use with caution in patients with a history of seizures.
  • Suicide: The possibility of a suicide attempt is inherent in schizophrenia and in bipolar I disorder, and close supervision of high-risk patients should accompany drug therapy

[edit] INTERACTIONS

  • Due to hypotensive effects, hypotensive effects of other drugs with this potential may be enhanced.
  • Effects of levodopa and dopamine agonists may be antagonized

[edit] PREGNANCY AND LACTATION

Pregnancy Category C (US). Risperidone should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.

Nursing Mothers: Risperidone is excreted in breast milk. It is recommended that women receiving Risperidone should not breast-feed.

[edit] SIDE EFFECTS

Adverse reactions include: Insomnia/somnolence, appetite increased and weight gain, fatigue, rhinitis, upper respiratory tract infection, vomiting, coughing, urinary incontinence, constipation, fever, dose-dependent extrapyramidal symptoms (including Parkinsonism, akathisia, dystonia, and tardive dyskinesia), incresed prolactin that leads to sexual dysfunction and breast disorders (oligomenorrhea, erectile dysfunction, galactorrhea, sexual dysfunction, ejaculation disorder, gynecomastia, breast discomfort, menstruation irregular, menstruation delayed, menstrual disorder), abdominal pain, anxiety, nausea, dizziness, dry mouth, tremor, rash, and dyspepsia.

[edit] RELATED LINKS

Antipsychotics (Typical and Atypical): pharmacology, indications and adverse effects

[edit] BIBLIOGRAPHY

[edit] REFERENCES