Risperidone is 3-2-[2-4-(6-fluoro-1,2-bezisoxazol-3-yl)-1-piperidinyl]ethyl-6,7,8,9-tetrahydro-2-methyl-4H-pyridol[1,2-α]pyrimidin-4-one.
Antipsychotic agent.
Pharmacology: Risperidone is a benzisoxazole derivative.
Mechanism of Action: Risperidone's antipsychotic activity is attributed to its antagonistic activity at both dopamine (D2 subtype) and serotonin (5HT2 subtype) receptors. Risperidone is also an antagonist of α1 and α2 and H1-receptor subtypes which mediate non-antipsychotic effects of risperidone.
Pharmacodynamics: Risperidone has been demonstrated to be efficacious in improving hallucinatory behaviour, paranoia, bizarre thought, content and conceptual disorganization when administered over a short term to patients of schizophrenia. During initiation of therapy, orthostatic hypotension can occur due to α-adrenergic receptor antagonism.
Pharmacokinetics: Absorption after oral administration is rapid and ranges up to 85% of the given dose. The absolute oral bioavailability of risperidone is approximately 70%. Plasma protein-binding is about 90%. Risperidone is extensively metabolized by the hepatic microsomal CYP-450 2D6 enzyme to 9-hydroxy-risperidone, an active metabolite. Tmax=1-3 hrs. Half-life of elimination ranges from 3-20 hrs for the parent drug and 21-30 hrs for the metabolite.
Acute schizophrenia; chronic schizophrenia; other psychoses; affective symptomatology of schizophrenia.
Adults: 1 mg twice daily on day 1; 2 mg twice daily on day 2 and 3 mg twice daily on day 3. Stabilize for 1 week. Further dose adjustment to be done only after 1 week at increments of 1 mg twice daily with maximum dose not to exceed 8 mg/day. If tardive dyskinesia occurs, discontinue risperidone.
Elderly: 0.5 mg twice daily on day 1; increase by 0.5 mg to achieve 1-2 mg twice daily.
Patients may be prone to profound hypotension in the presence of hepatic or renal disease.
Clinical experience is limited. No fatalities have been reported so far. Management consists of airway establishment, gastric lavage, activated charcoal administration, continuous ECG monitoring for proarrhythmia. No specific antidote is available. Supportive measures are the mainstay of therapy.
Hypersensitivity to risperidone.
In AMI, IHD, heart failure, conduction abnormality, treatment with antihypertensive medications, conditions pre-disposing to hypotension ie, dehydration, hypovolemia, risperidone is to be used cautiously. Epilepsy, hyperprolactinemia, parkinsonism, old age, renal and hepatic impairment are other conditions which require careful follow-up during risperidone therapy. Monitoring for development of neuroleptic malignant syndrome and tardive dyskinesia is essential and withdraw risperidone if these occur.
Risperidone occasionally prolongs the QT interval. Although confirmed cases of proarrhythmic effect due to risperidone are not yet reported, caution should be exercised.
Use in pregnancy & lactation: There are no adequate and well-controlled studies. Therefore, risperidone should only be used if the potential benefit justifies the potential risk to the foetus/neonate.
Use in children: Safety in children <15 years is not established.
There are no adequate and well-controlled studies. Therefore, risperidone should only be used if the potential benefit justifies the potential risk to the foetus/neonate.
Common: Extrapyramidal symptoms (exclusively in doses >6 mg/day), tremor, rigidity, hypokinesia, dystonia, ataxia/gait disturbance, dizziness, constipation, anxiety, somnolence, rash, rhinitis, tachycardia.
Rare: Arthralgia, aggressive reaction, visual disturbances.
CNS active drugs, levodopa, antihypertensive agents, alcohol, carbamazepine (increased clearance of risperidone). Clozapine (decreased clearance of risperidone).
Keep below 35°C, in a dry place. Protect from light.
N05AX08 - risperidone ; Belongs to the class of other antipsychotics.
FC tab 1 mg x 10 x 10's. 2 mg x 10 x 10's.
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