Clinical studies of risperidone tablets in the treatment of schizophrenia did not include sufficient numbers of patients aged 65 and over to determine whether or not they respond differently than younger patients. Other reported clinical experience has not identified differences in responses between elderly and younger patients. In general, a lower starting dose is recommended for an elderly patient, reflecting a decreased pharmacokinetic clearance in the elderly, as well as a greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or other drug therapy [see Clinical Pharmacology (12.3) and Dosage & Administration (2.4, 2.5)] . While elderly patients exhibit a greater tendency to orthostatic hypotension, its risk in the elderly may be minimized by limiting the initial dose to 0.5 mg twice daily followed by careful titration [see Warnings and Precautions (5.7)] . Monitoring of orthostatic vital signs should be considered in patients for whom this is of concern.
This drug is substantially excreted by the kidneys, and the risk of toxic reactions to this drug may be greater in patients with impaired renal function. Because elderly patients are more likely to have decreased renal function, care should be taken in dose selection, and it may be useful to monitor renal function [see Dosage & Administration (2.4)] .
In patients with moderate to severe (Clcr 59 to 15 mL/min) renal disease, clearance of the sum of risperidone and its active metabolite decreased by 60%, compared to young healthy subjects. Risperidone tablets doses should be reduced in patients with renal disease [see Dosage and Administration (2.4)] .
While the pharmacokinetics of risperidone in subjects with liver disease were comparable to those in young healthy subjects, the mean free fraction of risperidone in plasma was increased by about 35% because of the diminished concentration of both albumin and α 1 -acid glycoprotein. Risperidone tablets doses should be reduced in patients with liver disease [see Dosage and Administration (2.4)] .
Patients with Parkinsons Disease or Dementia with Lewy Bodies can experience increased sensitivity to risperidone tablets. Manifestations can include confusion, obtundation, postural instability with frequent falls, extrapyramidal symptoms, and clinical features consistent with neuroleptic malignant syndrome.
Risperidone tablets are not a controlled substance.
Risperidone tablets have not been systematically studied in animals or humans for its potential for abuse. While the clinical trials did not reveal any tendency for any drug-seeking behavior, these observations were not systematic and it is not possible to predict on the basis of this limited experience the extent to which a CNS-active drug will be misused, diverted, and/or abused once marketed. Consequently, patients should be evaluated carefully for a history of drug abuse, and such patients should be observed closely for signs of risperidone tablets misuse or abuse (e.g., development of tolerance, increases in dose, drug-seeking behavior).
Risperidone tablets have not been systematically studied in animals or humans for its potential for tolerance or physical dependence.
Premarketing experience included eight reports of acute risperidone tablets overdosage with estimated doses ranging from 20 to 300 mg and no fatalities. In general, reported signs and symptoms were those resulting from an exaggeration of the drug’s known pharmacological effects, i.e., drowsiness and sedation, tachycardia and hypotension, and extrapyramidal symptoms. One case, involving an estimated overdose of 240 mg, was associated with hyponatremia, hypokalemia, prolonged QT, and widened QRS. Another case, involving an estimated overdose of 36 mg, was associated with a seizure.
Postmarketing experience includes reports of acute risperidone tablets overdosage, with estimated doses of up to 360 mg. In general, the most frequently reported signs and symptoms are those resulting from an exaggeration of the drug’s known pharmacological effects, i.e., drowsiness, sedation, tachycardia, hypotension, and extrapyramidal symptoms. Other adverse reactions reported since market introduction related to risperidone tablets overdose include prolonged QT interval and convulsions. Torsade de pointes has been reported in association with combined overdose of risperidone tablets and paroxetine.
For the most up to date information on the management of risperidone tablets overdosage, contact a certified poison control center (1-800-222-1222 or www.poison.org). Provide supportive care including close medical supervision and monitoring. Treatment should consist of general measures employed in the management of overdosage with any drug. Consider the possibility of multiple drug overdosage. Ensure an adequate airway, oxygenation, and ventilation. Monitor cardiac rhythm and vital signs. Use supportive and symptomatic measures. There is no specific antidote to risperidone tablets.
Risperidone tablets, USP contain risperidone USP, an atypical antipsychotic belonging to the chemical class of benzisoxazole derivatives. The chemical designation is 3-[2-[4-(6-fluoro-1,2- benzisoxazol-3-yl)-1-piperidinyl]ethyl]-6,7,8,9-tetrahydro-2-methyl-4H-pyrido[1,2-a]pyrimidin-4-one. Its molecular formula is C 23 H 27 FN 4 O 2 and its molecular weight is 410.49. The structural formula is:
Risperidone USP is a white to slightly beige powder. It is practically insoluble in water, freely soluble in methylene chloride, and soluble in methanol and 0.1 N HCl.
Risperidone tablets, USP are for oral administration and available in 0.25 mg (orange), 0.5 mg (orange), 1 mg (white), 2 mg (yellow), 3 mg (orange), and 4 mg (brown) strengths. Risperidone tablets contain the following inactive ingredients: colloidal silicon dioxide, hypromellose, lactose monohydrate, magnesium stearate, microcrystalline cellulose, propylene glycol (except 1 mg), sodium lauryl sulphate, sodium starch glycolate and polyethylene glycol (1 mg). Tablets of 0.25 mg, 0.5 mg, 2 mg, 3 mg, and 4 mg also contain talc and titanium dioxide. 0.25 mg, 0.5 mg, and 3 mg tablets contain FD&C Yellow # 6 aluminum lake, the 2 mg tablets contain yellow iron oxide; the 4 mg tablets contain iron oxide red.
The mechanism of action of risperidone in schizophrenia is unclear. The drug’s therapeutic activity in schizophrenia could be mediated through a combination of dopamine Type 2 (D 2 ) and serotonin Type 2 (5HT 2 ) receptor antagonism. The clinical effect from risperidone results from the combined concentrations of risperidone and its major metabolite, 9-hydroxyrisperidone (paliperidone) [see Clinical Pharmacology ( 12.3)] . Antagonism at receptors other than D 2 and 5HT 2 may explain some of the other effects of risperidone [see Clinical Pharmacology ( 12.1)] .
Risperidone is a monoaminergic antagonist with high affinity (Ki of 0.12 to 7.3 nM) for the serotonin Type 2 (5HT 2 ), dopamine Type 2 (D 2 ), α 1 and α 2 adrenergic, and H 1 histaminergic receptors. Risperidone showed low to moderate affinity (Ki of 47 to 253 nM) for the serotonin 5HT 1C , 5HT 1D , and 5HT 1A receptors, weak affinity (Ki of 620 to 800 nM) for the dopamine D 1 and haloperidol-sensitive sigma site, and no affinity (when tested at concentrations >10 -5 M) for cholinergic muscarinic or β 1 and β 2 adrenergic receptors.
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