Torendo Q-Tab Tác dụng

Pharmacology: Pharmacodynamics: Risperidone is an atypical antipsychotic of the benzisoxazole class (also known as a second generation antipsychotic). It is a selective antagonist of serotonin type 2 (5-HT2) and dopamine type 2 (D2) receptors. Risperidone binds also to alpha1-adrenergic receptors, and, with lower affinity, to H1-histaminergic and alpha2-adrenergic receptors. Risperidone has no affinity for cholinergic receptors. Although the drug is less likely to cause Parkinson's, dystonia and akathisia have occurred. According to the traditional hypothesis, antipsychotic drugs act through dopamine D2 receptor blockers and harmful extrapyramidal effects are also due to blockade of dopamine D2 receptors in the striatum. Like clozapine, risperidone has a high affinity for 5-HT2 receptors and like haloperidone, risperidone has a high affinity for dopamine D2 receptors. The exact mechanism of antipsychotic action is unknown, but appears to be much more complex than with most other antipsychotics. It is not clear whether the antipsychotic effect of risperidone is due to action on the dopamine D2 receptor or elsewhere. It is possible that some of the other potent effects of risperidone offset the activity of D2 to produce a "atypical drug" nature. Whereas typical antipsychotics are dopamine antagonists, the addition of serotonin (5-HT2) antagonists enhances efficacy for negative symptoms of schizophrenia and may reduce extrapyramidal symptoms. However, if the dose of risperidone exceeds 6 mg/kg/day, extrapyramidal effects are common. Risperidone has a sedative effect, so there may be interactions with analgesics and sedatives. In clinical studies, especially in people with schizophrenia, oral risperidone was at least as effective as typical (such as haloperidol) or atypical (such as olanzapine) antipsychotic agents, but risperidone was more effective than haloperidol in preventing relapse in outpatients after at least 1 year of treatment with either agent. Risperidone is particularly useful in patients already taking typical antipsychotics who experience extrapyramidal reactions because risperidone is less likely to cause this reaction. In the elderly with dementia, risperidone increases the risk of stroke.
Pharmacokinetics: Torendo Q-Tab dispersible tablets are bioequivalent to Torendo Q-Tab film-coated tablets.
Risperidone is metabolized to 9-hydroxy-risperidone, which has a similar pharmacological activity as risperidone.
Risperidone is well absorbed after oral administration. Food does not affect the rate or extent of absorption. Risperidone is extensively metabolized in the liver by cytochrome P450 II D6 catalysis to the major, active metabolite, 9-hydroxy-risperidone. It is as potent as risperidone in terms of receptor-binding activity and has a half-life of 20 ± 3 hours. Following oral administration of risperidone, peak plasma concentrations are reached within 1 hour. Oral bioavailability is 66 ± 28% in strong metabolizers and higher in weak metabolizers. Plasma protein binding was 89% for risperidone and 77% for the active metabolite. The volume of distribution of risperidone is 1-2 liters/kg. In extensive metabolisers, the half-life of risperidone was 3.2 ± 0.8 hours, the urinary excretion was 3 ± 2%, and the clearance was 5.5 ± 2 ml/min/kg. The active metabolite, 9-hydroxyrisperidone has a half-life of 20 ± 3 hours. The drug is eliminated mainly in the urine and to a lesser extent in the faeces. Risperidone and its metabolite 9-hydroxyrisperidone both pass into breast milk.