Antipsychotic Medications Anti-psychotic Drugs risperidone, Risperdal

Antipsychotic: risperidone, Risperdal

Generic Name: risperidone
Brand Name(s): Risperdal
Common Use: Antipsychotic

Risperidone, a benzisoxazole derivative, is a novel antipsychotic drug which binds with high affinity to the serotonin type 2 (5-HT2), dopamine D2, and alpha1-adrenergic receptors.

For the management of manifestations of schizophrenia. In controlled clinical trials, risperidone was found to improve both positive and negative symptoms.

Contraindications

In patients with a known hypersensitivity to the drug or the excipients of the product.

Adverse Side Effects

The most frequent adverse reactions observed during clinical trials with risperidone were insomnia, agitation, extrapyramidal disorder, anxiety, and headache (see Table III and Table IV). In some instances it has been difficult to differentiate adverse events from symptoms of the underlying psychosis.
The most serious adverse reactions were rare cases of syncope, cardiac arrhythmias, first degree AV-block, and seizures.
An estimated 9% of approximately 1800 patients who received risperidone in controlled clinical trials discontinued treatment due to adverse reactions. The more common events causing discontinuation included: psychiatric (4.1%): primarily psychosis, agitation, suicide attempt, somnolence; neurological (3.2%): primarily extrapyramidal disorder, dizziness; and cardiovascular (1.2%): primarily hypotension. Other events leading to discontinuation included: tachycardia/palpitations (0.6%), nervousness (0.4%), nausea (0.3%) and insomnia (0.3%). Parkinsonian side effects were usually mild and were reversible upon dose reduction and/or administration of antiparkinsonian medication.
Occasionally, orthostatic hypotension, orthostatic dizziness, and reflex tachycardia have been observed following the administration of risperidone, particularly with higher initial doses.
Risperidone elevated plasma prolactin levels. Associated manifestations, namely amenorrhea, galactorrhea, and menorrhagia, have occurred.
Weight gain, erectile dysfunction, ejaculatory dysfunction, orgastic dysfunction, and rash have also been observed during treatment with risperidone. In one study, in which testosterone levels were measured, testosterone decreased below the normal range in 6 out of 85 patients.
As with classical neuroleptics, cases of water intoxication, either due to polydipsia or to inappropriate secretion of antidiuretic hormone (ADH), have occasionally been reported during treatment with risperidone.

Listed (in decreasing order) are those events which showed deterioration during treatment compared to baseline in at least 10% of patients. Psychic: asthenia/lassitude/increased fatiguability, concentration difficulties, sleepiness/sedation, reduced duration of sleep, increased duration of sleep, failing memory, increased dream activity; Autonomic: orthostatic dizziness, constipation, nausea/vomiting, polyuria/polydipsia, palpitations/tachycardia, reduced salivation, accommodation disturbances, increased tendency to sweating, diarrhea; Other: weight gain, weight loss, amenorrhea, ejaculatory dysfunction, erectile dysfunction, diminished sexual desire, tension Headache, increased sexual desire, orgastic dysfunction.
Postmarketing: International postmarketing reporting revealed the following adverse drug reactions during risperidone treatment: edema, increased hepatic enzyme levels, skin manifestations of allergy including a case of Stevens-Johnson syndrome, systemic manifestations of allergy including a case of anaphylactic shock, neuroleptic malignant syndrome and rare cases of tardive dyskinesia, hypertension, leukopenia and priapism. Rarely, mild to moderate neutropenia associated in a few cases with thrombopenia has been reported. To date, a casual relationship to risperidone has not been established. As with other neuroleptics, sudden deaths have ben reported during risperidone treatment. Most of the patients had pre-existing cardiovascular disease or were morbidly obese. A relationship to risperidone has not been established at this time.

Overdose

A few cases of overdosing have been reported with risperidone; the estimated doses were between 20 and 300 mg. None of the cases was fatal. Symptoms observed were due to excessive pharmacological effects, namely drowsiness and sedation, tachycardia and hypotension, and extrapyramidal symptoms.

Since there is no specific antidote to risperidone, treatment is primarily supportive. Gastric lavage (after intubation, if the patient is unconscious) and administration of activated charcoal together with a laxative should be considered.

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