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Risperidone (Risperdal)

Test ID:

703949

CPT code:

80342

Synonyms:

•Risperdal®
•Risperdal® Consta

Clinical Use:

Monitor drug levels for optimal therapy

Test Information:

Risperidone is an antipsychotic agent belonging to the benzisoxazole derivatives class. The mechanism of action is unknown; however, antipsychotic activity may be mediated through a combination of dopamine (D2) and serotonic (5HT2) antagonism. Risperidone is well absorbed by the gut. It is extensively metabolized in the liver to a major active metabolite, 9-hydroxyrisperidone, which appears approximately equieffective with risperidone with respect to receptor binding activity. Consequently, the clinical effect of the drug likely results from the combined concentrations of risperidone and 9-OH-risperidone. The pharmacokinetics for the sum of the two, after single and multiple doses, were similar in both rapid and slow metabolizers, with an overall mean elimination half-life of about 20 hours. Steady-state concentrations are reached in five to six days. The plasma protein binding of risperidone and 9-OH-risperidone is about 90% and 77%, respectively. It has been reported that dosing with long-acting risperidone every two weeks produced lower peak levels than oral dosing, while trough concentrations did not differ between the two routes of administration.1 Chronic administration of carbamazepine with risperidone may increase the clearance of risperidone; whereas, chronic administration of clozapine with risperidone may decrease the clearance of risperidone. The primary side effects noted with risperidone are the extrapyramidal symptoms, such as spasmodic, intermittent contraction of facial, neck, or back muscles, but the incidence of these side effects is lower compared with other neuroleptic agents.

Specimen Type:

Serum

Requested Volume:

3.3 mL

Minimum Volume:

1.1 mL

Container Type:

Red-top tube. Do not use a gel-barrier tube. The use of gel-barrier tubes is not recommended due to slow absorption of the drug by the gel. Depending on the specimen volume and storage time, the decrease in drug level due to absorption may be clinically significant.