Risperdal M-Tab
Risperdal M-Tab - General Information
A selective blocker of dopamine D2 receptors and serotonin 5-HT2 receptors that acts as an atypical antipsychotic agent. It has been shown to improve both positive and negative symptoms in the treatment of schizophrenia. [PubChem]
Pharmacology of Risperdal M-Tab
Risperdal M-Tab is an atypical antipsychotic medication. It is most often used to treat delusional psychosis (including schizophrenia), but risperidone is also used to treat some forms of bipolar disorder and psychotic depression. It also has shown some success in treating symptoms of Asperger's Syndrome and autism. Risperdal M-Tab is now the most commonly prescribed antipsychotic medication in the United States.
Risperdal M-Tab for patients
PATIENT INFORMATION
Physicians are advised to discuss the following issues with patients for whom they prescribe RISPERDAL�:
Orthostatic Hypotension
Patients should be advised of the risk of orthostatic hypotension, especially during the period of initial
dose titration.
Interference With Cognitive and Motor Performance
Since RISPERDAL� has the potential toimpair judgment, thinking, or motor skills, patients should be cautioned
about operating hazardous machinery, including automobiles, until they are reasonably certain that RISPERDAL�
therapy does not affect them adversely.
Pregnancy
Patients should be advised to notify their physician if they become pregnant or intend to become pregnant during
therapy.
Nursing
Patients should be advised not to breast-feed an infant if they are taking RISPERDAL.
Risperdal M-Tab Interactions
The interactions of RISPERDAL and other drugs have not been systematically evaluated. Given the primary CNS effects of risperidone, caution should be used when RISPERDAL is taken in combination with other centrally acting drugs and alcohol.
Because of its potential for inducing hypotension, RISPERDAL may enhance the hypotensive effects of other therapeutic agents with this potential.
RISPERDAL may antagonize the effects of levodopa and dopamine agonists.
Amytriptyline does not affect the pharmacokinetics of risperidone or the active antipsychotic fraction. Cimetidine and ranitidine increased the bioavailability of risperidone, but only marginally increased the plasma concentration of the active antipsychotic fraction.
Chronic administration of clozapine with risperidone may decrease the clearance of risperidone.
Carbamazepine and Other Enzyme Inducers
In a drug interaction study in schizophrenic patients, 11 subjects received risperidone titrated to 6 mg/day for 3 weeks, followed by concurrent administration of carbamazepine for an additional 3 weeks. During co-administration, the plasma concentrations of risperidone and its pharmacologically active metabolite, 9-hydroxyrisperidone, were decreased by about 50%. Plasma concentrations of carbamazepine did not appear to be affected. The dose of risperidone may need to be titrated accordingly for patients receiving carbamazepine, particularly during initiation or discontinuation of carbamazepine therapy. Co-administration of other known enzyme inducers (e.g., phenytoin, rifampin, and phenobarbital) with risperidone may cause similar decreases in the combined plasma concentrations of risperidone and 9-hydroxyrisperidone, which could lead to decreased efficacy of risperidone treatment.
Fluoxetine and Paroxetine
Fluoxetine (20 mg QD) and paroxetine (20 mg QD) have been shown to increase the plasma concentration of risperidone 2.5-2.8 fold and 3-9 fold respectively. Fluoxetine did not affect the plasma concentration of 9-hydroxyrisperidone. Paroxetine lowered the concentration of 9-hydroxyrisperidone an average of 13%. When either concomitant fluoxetine or paroxetine is initiated or discontinued, the physician should re-evaluate the dosing of RISPERDAL. The effects of discontinuation of concomitant fluoxetine or paroxetine therapy on the pharmacokinetics of risperidone and 9-hydroxyrisperidone have not been studied.
Lithium
Repeated oral doses of risperidone (3 mg BID) did not affect the exposure (AUC) or peak plasma concentrations (Cmax) of lithium (n=13). Valproate Repeated oral doses of risperidone (4 mg QD) did not affect the pre-dose or average plasma concentrations and exposure (AUC) of valproate (1000 mg/day in three divided doses) compared to placebo (n=21). However, there was a 20% increase in valproate peak plasma concentration (Cmax) after concomitant administration of risperidone.
Digoxin
RISPERDAL (0.25 mg BID) did not show a clinically relevant effect on the pharmacokinetics of digoxin.
Drugs That Inhibit CYP 2D6 and Other CYPIsozymes
Risperidone is metabolized to 9-hydroxyrisperidone by CYP 2D6, an enzyme that is polymorphic in the population and that can be inhibited by a variety of psychotropic and other drugs. Drug interactions that reduce the metabolism of risperidone to 9-hydroxyrisperidone would increase the plasma concentrations of risperidone and lower the concentrations of 9-hydroxyrisperidone. Analysis of clinical studies involving a modest number of poor metabolizers (n 70) does not suggest that poor and extensive metabolizers have different rates of adverse effects. No comparison of effectiveness in the two groups has been made.
In vitro studies showed that drugs metabolized by other CYPisozymes, including 1A1, 1A2, 2C9, 2C19, and 3A4, are only weak inhibitors of risperidone metabolism. There were no significant interactions between risperidone and erythromycin.
Drugs Metabolized by CYP 2D6
In vitro studies indicate that risperidone is a relatively weak inhibitor of CYP 2D6. Therefore, RISPERDAL is not expected to substantially inhibit the clearance of drugs that are metabolized by this enzymatic pathway. In drug interaction studies, risperidone did not significantly affect the pharmacokinetics of donepezil and galantamine, which are metabolized by CYP 2D6.
Risperdal M-Tab Contraindications
RISPERDAL (risperidone) is contraindicated in patients with a known hypersensitivity to the product.
Additional information about Risperdal M-Tab
Risperdal M-Tab Indication: For the treatment of schizophrenia in adults and in adolescents, ages 13 to 17, and for the short-term treatment of manic or mixed episodes of bipolar I disorder in children and adolescents ages 10 to 17.
Mechanism Of Action: Blockade of dopaminergic D2 receptors in the limbic system alleviates positive symptoms of schizophrenia such as hallucinations, delusions, and erratic behavior and speech. Blockade of serotonergic 5-HT2 receptors in the mesocortical tract, causes an excess of dopamine and an increase in dopamine transmission, resulting in an increase in dopamine transmission and an elimination of core negative symptoms. Dopamine receptors in the nigrostriatal pathway are not affected by risperidone and extrapyramidal effects are avoided. Like other 5-HT2 antagonists, risperidone also binds at alpha(1)-adrenergic receptors and, to a lesser extent, at histamine H1 and alpha(2)-adrenergic receptors.
Drug Interactions: Not Available
Food Interactions: Not Available
Generic Name: Risperidone
Synonyms: Risperidona [Spanish]; Risperidonum [Latin]
Drug Category: Antipsychotics
Drug Type: Small Molecule; Approved
Other Brand Names containing Risperidone: Risperdal; Risperdal Consta; Risperdal M-Tab; Risperidal M-Tab; Risperin; Rispolept; Rispolin; Sequinan;
Absorption: Well absorbed. The absolute oral bioavailability of risperidone is 70% (CV=25%). The relative oral bioavailability of risperidone from a tablet is 94% (CV=10%) when compared to a solution.
Toxicity (Overdose): Symptoms of overdose include drowsiness, sedation, tachycardia, hypotension, and extrapyramidal symptoms. LD50=82.1mg/kg (orally in mice).
Protein Binding: 90%
Biotransformation: Hepatic.
Half Life: 3 hours
Dosage Forms of Risperdal M-Tab: Liquid Oral
Tablet, orally disintegrating Oral
Tablet Oral
Suspension, extended release Intramuscular
Solution Oral
Chemical IUPAC Name: 3-[2-[4-(6-fluoro-1,2-benzoxazol-3-yl)piperidin-1-yl]ethyl]-2-methyl-6,7,8,9-tetrahydropyrido[2,1-b]pyrimidin-4-one
Chemical Formula: C23H27FN4O2
Risperidone on Wikipedia: https://en.wikipedia.org/wiki/Risperidone
Organisms Affected: Humans and other mammals
