Do enzyme inducers modify haloperidol decanoate rate of release?

1. Plasma levels were monitored for about 18 months during therapy with haloperidol decanoate. When steady-state was reached, patients treated without enzyme inducers showed in their plasma concentrations a stable plateau and a very low fluctuation. Furthermore, doses were correlated to plasma levels (r = 0.9). 2. Contrary, patients treated with both haloperidol decanoate and enzyme inducers seemed to present in their plasma concentration a very large fluctuation with C min (plasma concentrations measured just before the injection) significantly lower than those of the other group. Moreover their C min values were excluded from the linear regression curve calculated between plasma levels and doses in patients without enzyme inducers. 3. Our data suggest a shortening of the absorption half-time of haloperidol. In this case, it seems necessary to diminish the interval between injections than to give higher dosage in order to maintain plasma concentrations.