Interindividual variation of serum haloperidol concentrations in Japanese patients--clinical considerations on steady-state serum level-dose ratios.
OBJECTIVE
Marked interpatient variability in haloperidol (HAL) level-dose (L/D) ratios makes it difficult to use the administered dose for predicting serum concentrations.


OBJECTIVE
To investigate the effect of dose, age, total body weight and co-medication on steady-state HAL L/D ratios.


METHODS
Retrospective analysis of dose and HAL blood level data from 168 patients.


RESULTS
The HAL L/D ratio decreased curvilinearly with increasing daily dose of HAL. The patients treated with concomitant antiparkinsonian drugs showed a mean HAL L/D ratio that was 24.9% higher than those without antiparkinsonian drugs. The patients treated with concomitant antiepileptic drugs showed a mean HAL L/D ratio that was 27.2% lower than those without antiepileptic drugs. The mean HAL L/D ratio of patients treated with concomitant CYP2D6 substrates was not significantly different from those without CYP2D6 substrates.


CONCLUSIONS
There is a wide interindividual variability in blood levels of HAL in patients given the same dose. Routine monitoring of HAL serum level is useful, especially in patients who require associated antiepileptic and/or antiparkinsonian medication.
Yukawa
E
E
Laboratory of Evidence-Based Pharmacotherapy, College of Pharmaceutical Sciences, Daiichi University, Fukuoka, Japan. yukawa@daiichi-cps.ac.jp
Ichimaru
R
R
Maki
T
T
Matsunaga
K
K
Anai
M
M
Yukawa
M
M
Higuchi
S
S
Goto
Y
Y
D000328:Adult; D000368:Aged; D014150:Antipsychotic Agents / Q000008:administration & dosage / Q000097:blood*; D005260:Female; D006220:Haloperidol / Q000008:administration & dosage / Q000097:blood*; D006801:Humans; D007564:Japan; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies
D014150:Antipsychotic Agents; D006220:Haloperidol