The goal of this study was to assess in human liver microsomes the inhibitory capacity of commonly used antipsychotics on the most prominent CYP450 drug metabolizing enzymes (CYP1A2, CYP2C9, CYP2D6, and CYP3A). Chlorpromazine was the only antipsychotic that inhibited CYP1A2 activity (
In contrast to conventional neuroleptics, atypical antipsychotics have been shown to be effective against both positive and negative symptoms of schizophrenia while showing a reduced propensity to induce extrapyramidal effects [
In this paper we have assessed the potential for nine of the most commonly used atypical antipsychotics (clozapine, olanzapine, iloperidone, quetiapine, haloperidol, chlorpromazine, levomepromazine, thioridazine, and risperidone) and abaperidone (7-[3-[4-(6-fluoro-1,2-benzisoxazol-3-yl)-piperidin-1-yl]propoxy]-3-(hydroxymethyl)chromen-4-one; FI-8602), an underdevelopment compound with a potentially atypical antipsychotic profile [
Abaperidone and iloperidone were gifts from Centro de Investigación Farmacéutica, Grupo Ferrer (Barcelona, Spain). Chlorpromazine, levomepromazine, thioridazine, haloperidol, risperidone, clozapine, quinidine, sulphaphenazole, ketoconazole, diclofenac, furafylline, phenacetine, and acetaminophen were purchased from Sigma Chemical Co. (Madrid, Spain). Midazolam, 1'-hydroxy-midazolam, and 4-hydroxymidazolam were supplied by Hoffman-La-Roche (Basel, Switzerland). Bufuralol and 1′-hydroxybufuralol were obtained from Ultrafine Chemicals (Manchester, England), 4-hydroxydiclofenac from Gentest Corp (Woburn, MA), -quetiapine from Astra Zeneca (Macclesfield, Chesire, UK), and olanzapine from Lilly Laboratories (Indianapolis, IN).
Methanol and acetonitrile were of HPLC grade (Merck, Barcelona, Spain). Acetic and formic acids were of analytical grade and supplied by Merck (Barcelona, Spain). Glucose-6-phosphatedehydrogenase, glucose-6-phosphate, and NADPH were purchased from Roche Diagnostics SL (Barcelona, Spain). All other chemicals and reagents used were of the highest commercially available quality. Water was filtered by a Milli Q water system from Millipore Ibérica, S.A. (Madrid, Spain).
Chromatographic separation was performed with a system consisting of a Hewlett-Packard (HP) 1100 series (Agilent Technologies Spain S.L., Madrid, Spain) that had a degasser (model G1322A), quaternary pump (model G1311A), autosampler (model G1313A), column oven compartment (model G1316A), ultraviolet/visible detector (model G1315A), and fluorescence detector (model G and a mass spectrometer engine (model G1946A). A computer-assisted HP G2710AA LC/MS ChemStation (Agilent Technologies Spain S.L., Madrid, Spain) was used to operate modules and facilitate data management.
Phenacetin and its metabolite paracetamol were separated on a Hypersil BDS C18, 3
Bufuralol and its metabolite 1′-hydroxybufuralol were separated on an Ultrasphere ODS, 3
Diclofenac and its metabolite 4′-hydroxydiclofenac were separated on a Hypersil BDS C18, 3
The mass spectrometer was run in the positive ion mode. Nitrogen as the drying gas was supplied at a flow of 10 L/minutes and at a temperature of 350°C. The capillary voltage was adjusted to 4100 V. To quantitate midazolam, 4-hydroxymidazolam, and 1′-hydroxymidazolam, the mass spectrometer was operated in the selected ion-monitoring mode (SIM) with a dwell time of 229 msec. The eluant from HPLC was introduced into the source via the electrospray interface, generating the positively charged pseudomolecular ions (MH+) at m/z 326 and 342.
Inhibition studies on four different CYP isoform-specific substrates were carried out in human liver microsomes (Gentest Corporation, Woburn, MA). Assessed reactions were phenacetin O-deethylation for CYP1A2,
The conditions of the incubation reactions as well as the concentration of the substrate reaction probes utilized were established based on previous CYP450 inhibition studies by our group in human liver microsomes [
The effect of antipsychotics on the rate of CYP-catalyzed probe substrates was expressed as a percentage of the control activity with no antipsychotic present. The concentration of inhibitor causing 50% reduction of activity relative to the appropriate control value (IC50) was calculated by interpolation of a regression line of the log concentration versus percent inhibition plot over at least three concentrations of inhibitor.
The chromatographic conditions efficiently separated the compounds of interest in all the assays. Calibration curves were linear (coefficients of correlation
The incubation of 100
Inhibition of CYP1A2-mediated phenacetin O-deethylation (a), CYP2D6-mediated bufurarol 1-hydroxylation (b), and CYP3A-mediated midazolam 1′- (c) and 4′-hydroxylation (d) by atypical antipsychotics. Drugs depicted are clozapine (♦), olanzapine (●), iloperidone (+), quetiapine (○), haloperidol (
Levomepromazine, chlorpromazine, and thioridazine were significant inhibitors of CYP2D6, showing IC50 values of 25.5, 20, and 3.5
We could not identify any inhibitors of the CYP2C9 activity under our experimental conditions.
The observed CYP3A inhibition rates were different depending on the measured metabolite. Thus, olanzapine (
Given the
Inhibitory effect of atypical antipsychotics on human liver microsomal CYP450 activity.
Antipsychotic |
|
a
|
bTherapeutic range ( |
cInhibitory potency |
---|---|---|---|---|
CYP1A2 | ||||
Chlorpromazine | 75.7 | 4.75 | 0.1–1 | 0.1158 |
CYP2D6 | ||||
Levomepromazine | 60.6 | 12.75 | 0.05–0.2 | 0.0098 |
Chlorpromazine | 65.5 | 10.0 | 0.1–1 | 0.0550 |
Thioridazine | 73.2 | 1.75 | 0.5–5 | 1.5714 |
CYP3A (1-hydroxylation) | ||||
Olanzapine | 77.1 | 7.30 | 0.06–0.25 | 0.0212 |
Risperidone | 70.0 | 10.35 | 0.04–0.15 | 0.0092 |
Levomepromazine | 58.2 | 15.0 | 0.05–0.2 | 0.0083 |
CYP3A (4′-hydroxylation) | ||||
Olanzapine | 58.8 | 21.1 | 0.06–0.25 | 0.0073 |
Haloperidol | 55.4 | 1.38 | 0.01–0.04 | 0.0181 |
Interestingly, abaperidone did not cause a significant inhibition of any of the CYP enzymes assayed. This is a pharmacologically active substance underdevelopment, which therefore appears to be a remarkably safe agent with regard to CYP-mediated drug interactions, the main mechanism underlying interactions involving atypical antipsychotics [
In summary, the results show that several commonly used atypical antipsychotics exerted a significant
The authors state that the present work was funded in part by Ferrer International (Barcelona, Spain), which is developing one of the tested compounds, abaperidone (7-[3-[4-(6-Fluoro-1,2-benzisoxazol-3-yl)-piperidin-1-yl]propoxy]-3-(hydroxymethyl)chromen-4-one; FI-8602), as an atypical antipsychotic for the treatment of schizophrenia.
This work was supported in part by Ferrer International (Barcelona, Spain) and Grants GR10022 from Junta de Extremadura, Consejería de Economía, Comercio e Innovación, Mérida, Spain, and PRIS11003 from FUNDESALUD, Mérida, Spain.