Risperidone
Risperidone (Risperdal)
Risperidone
(ris- PAIR-ih-dohn)
Pregnancy Category: C Risperdal (Rx)

Classification: Antipsychotic

Action/Kinetics: Mechanism may be due to a combination of antagonism of dopamine (D ₂) and serotonin (5-HT ₂) receptors. Also has high affinity for the alpha-1, alpha-2, and histamine-1 receptors. Metabolized significantly in the liver to the active metabolite 9-hydroxyrisperidone, which has equal receptor-binding activity as risperidone. Thus, the effect is likely due to both the parent compound and the metabolite. Food does not affect either the rate or extent of absorption. The ability to convert risperidone to 9-hydroxyrisperidone is subject to genetic variation. A low percentage of Asians have the ability to metabolize the drug. Peak plasma levels, risperidone: 1 hr; peak plasma levels, 9-hydroxyrisperidone: 3 hr for extensive metabolizers and 17 hr for poor metabolizers. t 1/2, risperidone and 9-methylrisperidone: 3 and 21 hr, respectively, for extensive metabolizers and 20 and 30 hr, respectively, for poor metabolizers. Clearance is decreased in geriatric clients and in clients with hepatic and renal impairment.

Uses: Treatment of psychotic disorders.

Contraindications: Lactation.

Special Concerns: Use with caution in clients with known CV disease (including history of MI or ischemia, heart failure, conduction abnormalities), cerebrovascular disease, and conditions that predispose the client to hypotension (e.g., dehydration, hypovolemia, use of antihypertensive drugs). Use with caution in clients who will be exposed to extreme heat or when taken with other CNS drugs or alcohol. Greater risk of orthostatic hypotension, aspiration pneumonia, and toxic effects in geriatric clients with impaired renal function. The effectiveness of risperidone for more than 6-8 weeks has not been studied. Safety and effectiveness have not been established for children.

Side Effects: Neuroleptic malignant syndrome: Hyperpyrexia, muscle rigidity, altered mental status, autonomic instability (i.e., irregular pulse or BP, tachycardia, diaphoresis, cardiac dysrhythmia), elevated CPK, rhabdomyolysis, acute renal failure, death. CNS: Tardive dyskinesia (especially in geriatric clients), somnolence, insomnia, agitation, anxiety, aggressive reaction, extrapyramidal symptoms, headache, dizziness, increased dream activity, decreased sexual desire, nervousness, impaired concentration, depression, apathy, catatonia, euphoria, increased libido, amnesia, increased duration of sleep, dysarthria, vertigo, stupor, paresthesia, confusion. GI: Constipation, nausea, dyspepsia, vomiting, abdominal pain, increased or decreased salivation, toothache, anorexia, flatulence, diarrhea, increased appetite, stomatitis, melena, dysphagia, hemorrhoids, gastritis. CV: Prolongation of the QT interval that might lead to torsades de pointes. Orthostatic hypotension, tachycardia, palpitation, hypertension or hypotension, AV block, MI. Respiratory: Rhinitis, coughing, URI, sinusitis, pharyngitis, dyspnea. Body as a whole: Arthralgia, back pain, chest pain, fever, fatigue, rigors, malaise, edema, flu-like symptoms, increase or decrease in weight. Hematologic: Purpura, anemia, hypochromic anemia. GU: Polyuria, polydipsia, urinary incontinence, hematuria, dysuria, menorrhagia, orgastic dysfunction, dry vagina, erectile dysfunction, nonpuerperal lactation, amenorrhea, female breast pain, leukorrhea, mastitis, dysmenorrhea, female perineal pain, intermenstrual bleeding, vaginal hemorrhage failure to ejaculate. Dermatologic: Rash, dry skin, seborrhea, increased pigmentation, increased or decreased sweating, acne, alopecia, hyperkeratosis, pruritus, skin exfoliation. Ophthalmic: Abnormal vision, abnormal accommodation, xerophthalmia. Miscellaneous: Increased prolactin, photosensitivity, diabetes mellitus, thirst, myalgia, epistaxis.

Laboratory Test Alterations: CPK, serum prolactin, AST, ALT. Hyponatremia.

Overdose Management: Symptoms: Exaggeration of known effects, especially drowsiness, sedation, tachycardia, hypotension, and extrapyramidal symptoms. Treatment: Establish and secure airway, and ensure adequate oxygenation and ventilation. Follow gastric lavage with activated charcoal and a laxative. Monitor CV system, including continuous ECG readings. Provide general supportive measures. Treat hypotension and circulatory collapse with IV fluids or sympathomimetic drugs; however, do not use epinephrine and dopamine, as beta stimulation may worsen hypotension due to risperidone-induced alpha blockade. Anticholinergic drugs can be given for severe extrapyramidal symptoms.

Drug Interactions: Carbamazepine / Risperidone clearance following chronic use of carbamazepine Clozapine / Risperidone clearance following chronic use of clozapine Levodopa / Risperidone antagonizes the effects of levodopa and dopamine agonists

How Supplied: Solution: 1 mg/mL; Tablet: 0.25 mg, 0.5 mg, 1 mg, 2 mg, 3 mg, 4 mg

Dosage
?Oral Solution, Tablets Antipsychotic.
Adults, initial: 1 mg b.i.d. Once daily dosing can also be used. Can be increased by 1 mg b.i.d. on the second and third days, as tolerated, to reach a dose of 3 mg b.i.d. by the third day. Further increases in dose should occur at intervals of about 1 week. Maximal effect: 4-6 mg/day. Doses greater than 6 mg/day were not shown to be more effective and were associated with greater incidence of side effects. Safety of doses greater than 16 mg/day have not been studied. Maintenance: Use lowest dose that will maintain remission. The initial dose is 0.5 mg b.i.d. for clients who are elderly or debilitated, those with severe renal or hepatic impairment, and those predisposed to hypotension or in whom hypotension would pose a risk. Dosage increases in these clients should be in increments of 0.5 mg b.i.d. Dosage increases above 1.5 mg b.i.d. should occur at intervals of about 1 week.