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Do enzyme inducers modify haloperidol decanoate rate of release?
G Pupeschi1, C Agenet, J C Levron
1Montperrin Hospital, Aix-en-Provence, France.
Progress in Neuro-Psychopharmacology & Biological Psychiatry
|December 1, 1994
Summary
Enzyme inducers significantly alter haloperidol decanoate plasma levels, causing large fluctuations. Adjusting injection intervals, not dosage, is recommended for stable haloperidol decanoate therapy.
Area of Science:
- Pharmacology
- Clinical Pharmacy
- Neuroscience
Background:
- Haloperidol decanoate is a long-acting injectable antipsychotic.
- Enzyme inducers can affect drug metabolism and efficacy.
- Understanding drug-drug interactions is crucial for therapeutic drug monitoring.
Purpose of the Study:
- To investigate the effect of enzyme inducers on haloperidol decanoate plasma concentrations.
- To assess the impact of enzyme inducers on the predictability of haloperidol decanoate dosing.
Main Methods:
- Plasma haloperidol levels were monitored for 18 months in patients receiving haloperidol decanoate.
- Patients were divided into groups with and without enzyme inducers.
- Correlation between haloperidol doses and plasma levels was analyzed.
Main Results:
- Patients without enzyme inducers showed stable plasma levels and a strong dose-correlation.
- Patients with enzyme inducers exhibited significant plasma concentration fluctuations and lower trough levels (Cmin).
- Cmin values in the enzyme inducer group deviated from the dose-concentration relationship observed in the other group.
Conclusions:
- Enzyme inducers appear to shorten the absorption half-time of haloperidol decanoate.
- Therapeutic drug monitoring suggests reducing injection intervals rather than increasing dosage to maintain stable plasma concentrations when using enzyme inducers.
- This finding has implications for optimizing haloperidol decanoate treatment in patients on concomitant enzyme-inducing medications.