Genotype and co-medication dependent CYP2D6 metabolic activity: effects on serum concentrations of aripiprazole, haloperidol, risperidone, paliperidone and zuclopenthixol.

PURPOSE: Therapeutic drug monitoring (TDM) of antipsychotics can aid in therapy optimization, explaining adverse effects or non-response. One reason for therapeutic failure or adverse effects is caused by genetic variations in the cytochrome P450 drug-metabolizing genes. The aim of this study was to evaluate the impact of CYP2D6 polymorphisms on steady-state serum concentrations of antipsychotics metabolized by CYP2D6, taking into account the co-medication with CYP2D6 inhibitors. METHODS: Serum and EDTA samples were collected from 82 psychiatric patients. After a liquid-liquid extraction, serum samples were analyzed using an ultra-high performance liquid chromatography-tandem mass spectrometric (UHPLC-MS/MS) method for quantification of the antipsychotics. CYP2D6 genotyping was performed using the Luminex xTAG® CYP2D6 Kit v3 (Luminex Corporation). Patients were divided into five phenotype subgroups by calculation of the activity score (AS): poor metabolizers (PM; AS 0), intermediate metabolizers (IM; AS 0.5-1), extensive metabolizers with slow activity (EM-s; AS 1-1.5), extensive metabolizers with fast activity (EM-f; AS 2), and ultra-rapid metabolizers (UM; AS >2). The influence of the phenotypes on the concentration-to-dose and metabolite-to-parent ratios was evaluated. RESULTS: Overall, 6.1 % UM (n = 5), 25.6 % EM-f (n = 21), 46.3 % EM-s (n = 38), 1.2 % EM-s/EM-f (n = 1), 6.1 % IM (n = 5), and 14.6 % PM (n = 12) were found, taking co-administration of strong and moderate CYP2D6 inhibitors into account (phenoconversion). It was demonstrated that CYP2D6 polymorphisms affect the serum concentrations of aripiprazole (n = 18), haloperidol (n = 11), risperidone (n = 20), and zuclopenthixol (n = 6), while no influence was seen on the paliperidone serum concentrations (n = 31). CONCLUSIONS: Even with a small number of patients per antipsychotic, the importance of CYP2D6 genotyping was still clearly stated. This study illustrates the high potential of combining TDM and CYP2D6 genotyping in clinical practice.

Characterisation of zuclopenthixol metabolism by in vitro and therapeutic drug monitoring studies.

OBJECTIVE: Zuclopenthixol pharmacokinetics is incompletely characterised. We investigated potential interactions mediated through cytochrome P450 enzymes. METHOD: In vitro, we examined the impact of CYP2D6 and CYP3A4 inhibitors on zuclopenthixol metabolism in microsomes from six human livers. Subsequently, we compared dose-corrected serum zuclopenthixol concentrations in 923 samples from a therapeutic drug monitoring database from patients prescribed oral (n = 490) or injected (n = 423) zuclopenthixol alone or with fluoxetine, paroxetine, levomepromazine or carbamazepine. RESULTS: In vitro fluoxetine, paroxetine, ketoconazole and quinidine all significantly inhibited zuclopenthixol metabolism. Ketoconazole and quinidine together abolished zuclopenthixol disappearance. Clinically, dose-corrected oral zuclopenthixol serum concentrations increased significantly, after adjustment, by 93%, 78% and 46% during co-treatment with fluoxetine, paroxetine and levomepromazine and decreased 67% with carbamazepine. Carbamazepine caused dose-dependent reductions in the oral zuclopenthixol concentration-dose ratio (P < 0.001), fluoxetine (P < 0.001) and paroxetine (P = 0.011) dose-dependent increases and levomepromazine an increase related to its serum concentration (P < 0.001). Results for injected zuclopenthixol were similar but not all reached statistical significance. CONCLUSION: The In vitro study suggests zuclopenthixol is metabolised primarily by CYP2D6 and CYP3A4. The clinical study supports this, demonstrating the impact of co-prescribed inhibitors or inducers. Guidelines should incorporate these interactions noting the potential for zuclopenthixol-related toxicity or treatment failure.

Zuclopenthixol levels in serum and breast milk.

Breast milk and serum samples were obtained from six psychotic patients 3 days-10 months after delivery. Five of the women were given zuclopenthixol PO daily, and one was given zuclopenthixol decanoate IM every 2 weeks. Zuclopenthixol was estimated in breast milk and serum by high performance liquid chromatography. The zuclopenthixol levels in milk were found to be 29% of the serum levels on average. Based on the drug levels found in milk, the daily dose to a suckling infant was estimated to be 0.5-5 micrograms zuclopenthixol, corresponding to a dose of 0.01-0.1 mg to an adult. It is not likely that such a low dose would cause any effects or side effects in the infant unless infants are very different from adults concerning metabolism or sensitivity to the drug. The suckling infants included in this study were apparently not influenced by the intake of zuclopenthixol with the milk.

Serum levels and clinical response in long-term pharmacotherapy with zuclopenthixol decanoate.

Twenty-six patients diagnosed as chronic schizophrenics were given injections of zuclopenthixol decanoate (cis(Z)-clopenthixol decanoate) 200 mg every 3 weeks for at least 6 months. Before treatment and on each day of injection the patients' mental state was assessed by Brief Psychiatric Rating Scale (BPRS), 18 items. A registration of side effects and basal laboratory data was also performed. Blood samples were drawn on each day of injection before injection and 3-7 days after injection (time of maximum concentration). Neuroleptic activity, which was considered equivalent to the concentration of zuclopenthixol, was determined in serum by radio-receptor assay (RRA). Based on amelioration scores greater than or equal to 50% on the BPRS, 15 patients were characterized as responders and 11 as non-responders. The responder group showed a statistically significant reduction in BPRS score, whereas this was not the case for the non-responders. Apart from a few patients, the serum concentrations showed a low intra-individual variation, but a relatively high inter-individual variation. The responder group had a significantly higher mean pre-injection concentration than the non-responder group, whereas no significant difference was found in day 3-7 concentrations. The fluctuation of the serum concentration expressed as the ratio between maximum (days 3-7) and minimum (pre-inj.) was found to be significantly lower for responders than for non-responders. Thus although the present study did not demonstrate a clear relationship between serum level and clinical effect, it indicates that the best antipsychotic effect is obtained with a serum concentration which fluctuates only slightly (the ratio max/min concentration not exceeding 2.1).

Zuclopenthixol decanoate in schizophrenia: serum levels and clinical state.

Serum concentrations of zuclopenthixol were determined in a group of 20 patients treated with a depot preparation, zuclopenthixol decanoate in Viscoleo. Clinical assessments according to a Clinical Global Impression (CGI) scale, Comprehensive Psychological Rating Scale (CPRS), 16-item subscale for schizophrenia, and the UKU side effect scale were performed on 3 consecutive days of injection. The serum concentrations showed a limited individual variation and a high and significant correlation between dose and serum concentration. One patient had a particularly high serum concentration of zuclopenthixol. This patient also had an elevated concentration of the N-dealkyl metabolite, but a low concentration of the sulphoxide. For serum concentrations versus clinical state and side effects some significant correlations were found. All correlations were positive, which means that the higher the serum concentration the poorer the clinical state of the patient. We think that this probably reflects a common clinical pattern of increasing the dose, when the antipsychotic response is unsatisfactory. The study also showed that for moderately ill patients, who were given the optimum dose of drug, the subgroup of patients not experiencing side effects had significantly lower serum concentrations than the subgroup with side effects.

Serum concentrations of the isomers of clopenthixol and a metabolite in patients given cis(Z)-clopenthixol decanoate in viscoleo.

Cis(Z)-clopenthixol decanoate in Viscoleo (Sordinol Depot, Cisordinol Depot, Clopixol Inj.) was given intramuscularly to nine schizophrenic patients with dosage intervals of 1 or 2 weeks. Serum concentrations of the two geometric isomers of clopenthixol and its N-dealkyl metabolite were recorded in two successive dosage intervals. Significant correlations were found for dose vs area under the serum concentration curve and vs serum concentrations measured on individual days. The last mentioned concentrations are good measures of the area under the serum concentration curve, which expresses the drug load of the patient. The serum concentration curves in two successive dosage intervals were very similar. Maximum serum concentration was seen 5-7 days after injection and the mean maximum/minimum fluctuation was 1.6 with the 2-week dosage interval. The finding of very low amounts of the trans(E)-isomers of clopenthixol and the N-dealkyl-metabolite shows that isomerization of the cis(Z)-compounds into the corresponding trans(E)-isomers does not take place within the organism.

Blood and plasma kinetics of cis(Z)-clopenthixol and fluphenazine in psychiatric patients after intramuscular injection of their decanoic esters.

Whole blood and plasma concentrations of active neuroleptic drugs were measured in eight schizophrenic outpatients who had received cis(Z)-clopenthixol decanoate in Viscoleo or fluphenazine decanoate in sesame oil by intramuscular injection. Whole blood and plasma concentrations were very similar, though there was a slight tendency for blood concentrations to be higher than plasma concentrations. Maximum concentrations appeared at 1 week after administration of cis(Z)-clopenthixol decanoate, whereas the highest concentrations after fluphenazine decanoate were seen at the end of the 3-week dosage interval. Some between-individual variation and a limited within-individual variation was seen.

Serum concentrations and clinical effect of zuclopenthixol in acutely disturbed, psychotic patients treated with zuclopenthixol acetate in Viscoleo.

Zuclopenthixol acetate, 5%, in Viscoleo was administered IM to 19 acutely disturbed, psychotic patients in doses of 50-150 mg. Fifteen patients received one injection, whereas four of the patients had two or three injections, usually with intervals of 3 days. The zuclopenthixol concentrations in serum were measured in series of samples taken from each patient during a 3-day period following the injection. In patients given identical doses serum concentrations of about the same order were obtained. Significant and good correlations were found between dose and maximal serum concentration and between dose and area under the serum concentration curve. The average serum concentration curve obtained when adjusting the data to a 100 mg dose has a maximum of 41 ng/ml after about 36 h, decreasing to 15 ng/ml after 72 h. A dose of 50-150 mg zuclopenthixol acetate in Viscoleo appeared to be sufficient for controlling the symptoms for most acutely disturbed, psychotic patients. The frequency of side effects, including extrapyramidal reactions, was low and the adverse reactions mostly mild, indicating that the risks for severe complications generally might be minimal. With a rapid onset of action, few and mild side effects, good tolerability at the injection site, and a duration of effect of 2-3 days, zuclopenthixol acetate in Viscoleo appears to offer advantages compared to conventional neuroleptic treatment in patients in whom an acute, calming effect is desired.

Maintenance therapy with zuclopenthixol decanoate: associations between plasma concentrations, neurological side effects and CYP2D6 genotype.

RATIONALE: Several antipsychotic drugs are metabolised by the polymorphic cytochrome P(450) CYP2D6. The impact of the polymorphism on the plasma levels and the occurrence of side effects have not been clearly established. OBJECTIVE: To investigate the impact of the CYP2D6 polymorphism on the steady-state plasma concentrations of zuclopenthixol and the occurrence of extrapyramidal side effects (EPS) and tardive dyskinesia (TD) during treatment with zuclopenthixol-decanoate. METHODS: Fifty-two clinically stable schizophrenic outpatients on monotherapy with zuclopenthixol-decanoate (100-400 mg/4 weeks) were genotyped for the CYP2D6 variants CYP2D6*3 and CYP2D6*4. Steady-state plasma levels of zuclopenthixol were analysed using high-performance liquid chromatography. Assessments of EPS, TD and psychopathology were performed twice with an 8-week interval using the extrapyramidal symptoms rating scale, the abnormal involuntary movement scale and the brief psychiatric rating scale. RESULTS: Thirty-five patients were homozygous extensive metabolisers (EMs), 13 were heterozygous EMs and 4 were poor metabolisers (PMs). While there were no significant genotype-related differences in the doses of zuclopenthixol decanoate, PMs as well as heterozygous EMs had significantly higher steady-state plasma levels of zuclopenthixol than homozygous EMs (median 9.5 nmol/l; 8.2 nmol/l and 5.9 nmol/l, respectively, P<0.05). The median dose-corrected plasma concentrations were 0.029, 0.038 and 0.048 nmol.l(-1).mg(-1) in homozygous EMs, heterozygous EMs and PMs, respectively, with statistically significant differences between homozygous EMs and heterozygous EMs ( P=0.014) and homozygous EMs and PMs ( P=0.03). Patients with neurological side effects were significantly older than patients without ( P=0.02 in case of parkinsonism and P=0.04 in case of TD). Mutant CYP2D6*3 and *4 alleles tended to occur more frequently in patients with neurological side effects. An odds ratio (OR) of 2.3 (95% confidence interval 0.7-6.9) for development of parkinsonism and an OR of 1.7 (95% confidence interval 0.5-4.9) for TD was calculated in an individual with at least one mutated allele. However, the ORs were not statistically significant. CONCLUSIONS: The higher zuclopenthixol steady-state plasma concentrations in heterozygous EM and PM schizophrenic patients receiving monotherapy with zuclopenthixol-decanoate than in homozygous EMs indicates a significant role of CYP2D6 in the systemic elimination of zuclopenthixol. The tendencies for patients carrying at least one mutated CYP2D6 gene to have an increased risk of parkinsonism and TD are in accordance with previous studies. Age was a significant risk factor for neurological side effects.

Liquid chromatographic analysis of the cis(Z)- and trans(E)-isomers of clopenthixol in human plasma using a novel solid phase extraction procedure.

A simple and highly sensitive high-performance liquid chromatographic (HPLC) method for the simultaneous determination of cis(Z)-clopenthixol and trans(E)-clopenthixol in human plasma has been developed. The chromatographic analysis was carried out isocratically on a reversed-phase column (C(8) 150 x 4.6 mm I.D., 5 microm) using a mixture of 25 mM phosphate buffer and acetonitrile (65:35 v/v, pH* 3.0) as the mobile phase, and ultraviolet detection at 230 nm. Plasma sample pretreatment was accomplished by means of an original solid-phase extraction (SPE) procedure carried out on cyanopropyl cartridges, with a high extraction yield and good selectivity. Under the optimum conditions, calibration graphs of spiked human plasma samples were obtained over the concentration ranges 1-300 ng ml(-1) for cis(Z)-clopenthixol and 1-200 ng ml(-1) for trans(E)-clopenthixol. The limit of detection (LOD) was 0.3 ng ml(-1) for both cis(Z)- and trans(E)-isomers of clopenthixol. The method was successfully applied to the determination of cis(Z)-clopenthixol and trans(E)-clopenthixol in plasma samples of schizophrenic patients undergoing therapy with zuclopenthixol.

Central D2 receptor occupancy and effects of zuclopenthixol acetate in humans.

Repeated positron emission tomography (PET) measurements of D2 receptor occupancy, plasma concentrations of zuclopenthixol and reaction time were performed in three healthy subjects after injection of 12.5 mg zuclopenthixol acetate (ZPTA) in an open study design. Five control subjects were examined for reaction time only. D2 receptor occupancy was 51%, 71% and 75% after 7 h and 75%, 83% and 87% after 31 h in the three subjects. The subjects reported sedation, but reaction time was not prolonged. After the low dose of 12.5 mg ZPTA, D2 receptor occupancy exceeded the 70% assumed to be required to induce antipsychotic effect. Extrapolation of data to a clinical dose interval indicates that 50-150 mg ZPTA should induce very high D2 receptor occupancy lasting several days after injection. Such high doses may be required to induce sedation and to avoid frequent intramuscular injections in acutely psychotic patients. However, the simultaneously induced very high D2 receptor occupancy calls for careful assessment of acute extrapyramidal symptoms.

HPLC-ESI-MS/MS determination of zuclopenthixol in a fatal intoxication during psychiatric therapy.

The first non-suicidal fatality due to intramuscular administration of Cisordinol (zuclopenthixol, ZPT) is described. A new, rapid, and sensitive method for the determination of ZPT in postmortem specimens has been developed. High performance liquid chromatography electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS) was employed for drug confirmation and quantitation. Sample clean up was performed using a simple liquid-liquid extraction procedure. The postmortem concentration of ZPT in heart blood was 0.68 microg/ml. Furthermore, zotepine, carbamazepine, and chlorprotixene were detected in body fluids. The proposed method enables the unambiguous identification and quantitation of ZPT and other neuroleptic drugs in clinical and forensic specimens.

LC/MS determination of bromazepam, clopenthixol, and reserpine in serum of a non-fatal case of intoxication.

Combined liquid chromatography and mass spectrometry (LC/MS) with a moving belt interface can be used as a rapid method for the determination of bromazepam, clopenthixol, and reserpine in serum samples obtained from cases of acute overdoses with combinations of these drugs. Low resolution detection limits are about 100 pg for the three drugs, while in high resolution mode the detection limit for bromazepam is shown to be at least 35 pg. Accurate masses were obtained in a serum sample within 5 ppm using high voltage scanning over a narrow mass range for about 10 ng of bromazepam and clopenthixol, respectively. Chemical deactivation of the belt was shown to effectively reduce memory effects and to improve the desorption characteristics of the belt leading to higher yields of evaporated intact molecules.

Concentrations of cis(Z)-clopenthixol and trans(E)-clopenthixol in a lethal case involving zuclopenthixol, diazepam, and cyamemazine.

cis(Z)-Clopenthixol and trans(E)-clopenthixol were determined by gas chromatography-mass spectrometry and high-performance liquid chromatography-diode-array detection in necropic samples from a postmortem case. The peripheral blood concentrations of cis(Z)-clopenthixol and trans(E)-clopenthixol were 278 and 177 ng/mL, respectively. The level of the active cis(Z)-isomer is within the toxic range. Other associated drugs' concentrations were within their therapeutic ranges. Postmortem redistribution of the drug and instability of the drug due to trans-isomerization were discussed.

Flow-injection chemiluminometric determination of some thioxanthene derivatives in pharmaceutical formulations and biological fluids using the [Ru(dipy)3(2+)]-Ce(IV) system.

A flow-injection (FI) methodology using tris(2,2'-dipyridyl)ruthenium(II), [Ru(dipy)3(2+)], chemiluminescence (CL) was developed for the rapid and sensitive determination of three thioxanthene derivatives, namely zuclopenthixol hydrochloride, flupentixol hydrochloride and thiothixene. The method is based on the CL reaction of the studied thioxanthenes with [Ru(dipy)3(2+)] and Ce(IV) in a sulfuric acid medium. Under the optimum conditions, calibration graphs were obtained over the concentration ranges 0.002-6 migrograms/ml for zuclopenthixol hydrochloride, 0.5-15 micrograms/ml for flupentixol hydrochloride and 0.05-7.5 micrograms/ml for thiothixene. The limits of detection (s/n = 3) were 4.2 x 10(-9) mol/l zuclopenthixol hydrochloride, 2 x 10(-8) mol/l flupentixol hydrochloride and 4.5 x 10(-8) mol/l thiothixene. The method was successfully applied to the determination of these compounds in dosage forms and biological fluids.

[The effect of serum monitoring on concentration of perphenazine and zuclopenthixole]. / Effekten af serumkontrol på koncentrationen af perfenazin og zuklopentixol.

The effect of therapeutic drug monitoring (TDM), including pharmacokinetic guidance, was examined in 994 psychiatric patients treated with perphenazine (Trilafon) or zuclopentixol (Cisordinol). Before monitoring of the serum level, half of the serum concentrations from patients given perphenazine tablets (466 patients) was below the therapeutic level, and about one third was above. For perphenazine depot (208 patients), almost no patients had a serum concentration below the therapeutic level whereas 40% had concentrations above. For zuclopentixol tablets (231 patienter) and zuclopentixol depot (163 patients), about 60% of the patients had concentrations above the therapeutic level. For all four groups, it was found that slightly more than half of the patients with serum concentrations outside the therapeutic level was reexamined. The dosage was changed in most of these patients (80-90%) in order to bring the concentration within the therapeutic level. Half of those in whom the dose was changed obtained concentrations within the therapeutic level. It is concluded that since the recommendations for changes of the dosage is followed to a wide extent, the therapeutic drug monitoring service does influence the treatment significantly.

Simultaneous determination of 25 common pharmaceuticals in whole blood using ultra-performance liquid chromatography-tandem mass spectrometry.

An ultra-performance liquid chromatography-tandem mass spectrometry method was developed and validated for the quantification of 25 common pharmaceuticals in whole blood. The selected pharmaceuticals represent the most frequently detected drugs in our forensic laboratory with basic properties such as analgesics, antidepressants, antihistamines, antihypertensives, antipsychotics and ß-blockers. Whole blood samples were extracted with butyl acetate after adjusting pH with 2M NaOH. The target analytes were separated on a 100 × 2.1 mm ACQUITY BEH 1.7 µm C18 column by a formic acid/acetonitrile gradient elution using a Waters ACQUITY Ultra-Performance Liquid Chromatography system. Quantification was performed on a Waters tandem quadrupole ACQUITY TQD using multiple reaction monitoring in positive mode. The analytes were eluted within 11 min. The limit of quantification (LOQ) ranged from 0.002 to 0.01 mg/kg depending on the analyte. A good linear behavior was achieved for all analytes in the range from LOQ to 1.0 or 2.0 mg/kg blood. The absolute recoveries were between 55-87% for all compounds except norfluoxetine (44%). The method showed acceptable precision and accuracy for almost all analytes. Only unstable compounds like levomepromazine, methylphenidate, mirtazapine, norfluoxetine and zuclopenthixol deviated more. The method was successfully applied to more than 200 authentic blood samples within a year from forensic investigations.

Serum concentrations of cis(Z)- and trans(E)-clopenthixol after administration of cis(Z)-clopenthixol and clopenthixol to human volunteers.

The serum concentrations of cis(Z)- and trans(E)-clopenthixol have been estimated in human volunteers by an HPLC-method after administration of a clopenthixol tablet, which contains the cis(Z)- and the trans(E)-isomers in the ratio 1/2, or a cis(Z)-clopenthixol tablet. The serum concentration curves obtained for the cis(Z)-isomer after administration of the two drug preparations were very similar, and thus independent of the presence of the trans(E)-isomer in one of the preparations. Likewise the biological half-lives and the areas under the serum concentration curves for cis(Z)-clopenthixol were similar after the two preparations. The biological half-life of cis(Z)-clopenthixol was as a mean 20 hours (12-29 hours) indicating that from a pharmacokinetic point of view a dosage interval of 24 hours is possible for most patients. The biological half-life of trans(E)-clopenthixol is found to be longer than that for cis(Z)-clopenthixol.