Objective. The interaction between carbamazepine and bromperidol was s
tudied in 13 schizophrenic inpatients. Methods: Before carbamazepine a
ddition, the subjects were taking bromperidol 12-24 mg.day(-1) for 1-2
0 weeks. Carbamazepine 400 mg.day(-1) was coadministered for 4 weeks,
and blood samplings were performed before carbamazepine addition and a
t weekly intervals after the addition. Plasma concentrations of brompe
ridol and its reduced metabolite were measured by highperformance liqu
id chromatography. Results: Carbamazepine significantly decreased plas
ma concentrations of both bromperidol and reduced bromperidol for all
weeks. On average, the plasma concentrations of bromperidol and reduce
d bromperidol at 4 weeks were 37% and 23% of the corresponding precarb
amazepine values. Despite these decreases in plasma concentration, the
Clinical Global Impression scores decreased slightly but significantl
y after carbamazepine addition. Conclusion: The present study suggests
that carbamazepine decreases plasma concentrations of bromperidol and
its reduced metabolite by inducing the metabolism of these compounds.
Nevertheless, adjunctive carbamazepine may be useful for schizophreni
c patients treated with bromperidol.