Equivalent switching dose from oral risperidone to risperidone long-acting injection: a 48-week randomized, prospective, single-blind pharmacokinetic study.
OBJECTIVE
Previous studies showed clinical benefit of risperidone long-acting injection in the treatment of schizophrenia. However, the equivalent switching dose from oral risperidone to risperidone long-acting injection was still in debate. This study, conducted among hospitalized patients, included a long-enough study period and optimal control of drug compliance to test the equivalent switching dose.


METHODS
Fifty symptomatic, stable hospitalized patients with DSM-IV schizophrenia were randomly assigned to receive either daily oral risperidone or risperi-done long-acting injection every 2 weeks. Those originally receiving an oral risperidone dose of 4 mg/day or less received 25 mg of risperidone long-acting injection, those taking an oral dose of more than 4 mg/day but of 6 mg/day or less received 37.5 mg of risperidone long-acting injection, and those taking more than 6 mg/day received 50 mg of risperidone long-acting injection. Assessments of clinical efficacy, side effects, metabolic safety, drug tolerance, and serum concentration of risperi-done metabolites were performed repeatedly. The study was conducted from March 2004 to May 2005.


RESULTS
Forty-five patients (90%) completed the study. There were no significant differences in Positive and Negative Syndrome Scale (PANSS) scores between the 2 groups, but the risperidone long-acting injection group showed reduced UKU Side Effect Rating Scale total scores (p = .048), Simpson-Angus Scale scores (p = .028), prolactin levels (p = .046), and serum concentrations of risperidone metabolites (p = .028). Among the risperidone long-acting injection group, patients who received either 25 mg q 2 weeks or 37.5 mg q 2 weeks of risperidone long-acting injection showed increased PANSS scores (p = .058), decreased serum metabolite concentrations (p = .028), and an increased tendency to relapse.


CONCLUSIONS
The results support good tolerability of risperidone long-acting injection, but it is suggested that the equivalent switching dose be adjusted as follows: those originally on an oral risperidone dose of 3 mg/day or less should receive 25 mg of risperidone long-acting injection, those taking an oral dose of more than 3 mg/day but of 5 mg/day or less should receive 37.5 mg, and those taking an oral dose of more than 5 mg/day should receive 50 mg of risperidone long-acting injection.
Bai
Ya Mei
YM
Department of Psychiatry, Taipei Veterans General Hospital, Taipei, Taiwan. ymbi@mail2000.com.tw
Ting Chen
Tzu
T
Chen
Jen-Yeu
JY
Chang
Wen-Ho
WH
Wu
Bojian
B
Hung
Chih Hung
CH
Kuo Lin
Wen
W
D000284:Administration, Oral; D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D007267:Injections / Q000009:adverse effects; D008297:Male; D008875:Middle Aged; D010146:Pain / Q000145:classification / Q000209:etiology; D010147:Pain Measurement; D017060:Patient Satisfaction; D011388:Prolactin / Q000097:blood; D011446:Prospective Studies; D018967:Risperidone / Q000008:administration & dosage* / Q000493:pharmacokinetics*; D012559:Schizophrenia / Q000188:drug therapy*; D016037:Single-Blind Method
D011388:Prolactin; D018967:Risperidone