Plasma clozapine concentrations predict clinical response in treatment-resistant schizophrenia.
Steady-state blood clozapine concentrations in 58 schizophrenic patients varied more than 45-fold (40-1911 ng/mL) after fixed-dose treatment (400 mg/day). Discriminant function analysis determined that a blood clozapine concentration of 420 ng/mL optimally distinguished responders from nonresponders. After 4 weeks of treatment, only 8% of those patients with a blood clozapine concentration < 420 ng/mL responded compared with 60% of those who had a blood clozapine concentration > 420 ng/mL. When plasma concentrations were increased above 420 ng/mL (by a double-blind random assignment procedure), nonresponders increased their response rate to 73% if their plasma concentrations at Week 12 exceeded 420 ng/mL compared with a response rate of 29% if their Week 12 levels remained below 420 ng/mL (chi 2 = 4.2, p < .04).
Department of Psychiatry and Human Behavior, University of California Irvine Medical Center, Orange 92668.
S G
SG
Potkin
R
R
Bera
B
B
Gulasekaram
J
J
Costa
S
S
Hayes
Y
Y
Jin
G
G
Richmond
D
D
Carreon
K
K
Sitanggan
B
B
Gerber
D000328:Adult; D003024:Clozapine / Q000008:administration & dosage / Q000097:blood*; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D004334:Drug Administration Schedule; D005260:Female; D006760:Hospitalization; D006801:Humans; D008297:Male; D011336:Probability; D011569:Psychiatric Status Rating Scales; D012559:Schizophrenia / Q000097:blood / Q000175:diagnosis / Q000188:drug therapy*; D012565:Schizophrenic Psychology; D016896:Treatment Outcome
D003024:Clozapine