Suggested therapeutic range (20-60 mcg/L) follows the recommendation of the AGNP (1). Similar ranges were confirmed in therapeutic levels that were taken in large numbers of patients (2). Add the sum of risperidone and 9 hydroxy risperidone (active metabolite) to calculate the therapeutic range. Paliperidone, which is used therapeutically, is 9 hydroxy risperidone.
Risperidone is an atypical antipsychotic. It is used to treat schizophrenia, bipolar disorder and irritability associated with autism. Common side effects include extrapyramidal movement disturbances, sleepiness, constipation and increases in weight. There is evidence for relationships between plasma concentrations of the drug and metabolite and effectiveness as well as extrapyramidal side-effects. The metabolite is active and has a longer half life and brackets (24 hours) then risperidone (4 hours). For the therapeutic range add both drug and metabolite together. A low metabolite to parent ratio (normal 4 to 23 with oral medication, 1-4 after i.m. Medication) indicates a different CYP2D6 genotype with poor metabolism. Fluoxetine inhibits CYP2D6 and increases risperidone concentrations.
- Hiemke C, et al. Consensus Guidelines for Therapeutic Drug Monitoring in Neuropsychopharmacology: Update 2017 [published correction appears in Pharmacopsychiatry. 2018 Jan;51(1-02):e1]. Pharmacopsychiatry. 2018;51(1-02):9–62. Doi:10.1055/s-0043-116492
- Jönsson AK, et al. Compilation of Serum Concentrations of 12 Antipsychotic Drugs in a Therapeutic Drug Monitoring Setting. Ther Drug Monit. 2019;41(3):348–356. doi:10.1097/FTD.00000000000005852.
Performed by LC-MS/MS