Placebo effects in adult and adolescent patients with schizophrenia: combined analysis of nine RCTs.

OBJECTIVE: To examine characteristics of placebo responders and seek optimal criteria of early improvement with placebo for predicting subsequent placebo response in patients with schizophrenia. METHOD: Data of 672 patients with schizophrenia randomized to placebo in nine double-blind antipsychotic trials were analyzed. Multiple logistic regression analyses were conducted to examine associations between placebo response at week 6 (i.e., a ≥ 25% reduction in the Positive and Negative Syndrome Scale [PANSS] score) and gender, age, study locations, baseline PANSS total or Marder 5-Factor scores, and per cent PANSS score reduction at week 1. Predictive power of improvement at week 1 for subsequent response was investigated; sensitivity and specificity of incremental 5% cutoff points between 5% and 25% reduction in the PANSS total score at week 1 were calculated. RESULTS: Per cent PANSS total score reduction at week 1 and lower PANSS Marder disorganized thought scores at baseline were significantly associated with subsequent placebo response. A 10% reduction in a per-protocol analysis or a 15% reduction in last-observation-carried-forward analysis in the PANSS total score at week 1 showed the highest predictive power. CONCLUSION: These findings are informative to identify potential placebo responders at the earliest opportunity for optimal trial design for schizophrenia.

Factors Affecting Steady-state Plasma Concentrations of Enantiomeric Mirtazapine and its Desmethylated Metabolites in Japanese Psychiatric Patients.

INTRODUCTION: This study evaluated the effects of the CYP2D6*10 genotype on steady-state plasma concentrations of enantiomeric mirtazapine (MIR) and N-desmethylmirtazapine (DMIR) in Japanese patients. METHODS: Subjects were 77 Japanese patients treated with racemic MIR. Steady-state plasma concentrations of MIR and DMIR enantiomers were measured using stereoselective liquid chromatography. Polymerase chain reaction was used to determine the CYP2D6 genotypes. RESULTS: After correcting for dose and body weight, smokers (n=15) had significantly lower S-(+)-MIR than nonsmokers (n=55) (15.1±17.8 vs. 23.9±17.8 ng/mL/mg/kg, Kruskal-Wallis test, p=0.034). One-way analysis of variance revealed that CYP2D6*10 homozygotes had significantly higher corrected plasma concentrations of S-(+)-MIR than the no-variant allele group (p=0.034). Multiple regression analysis revealed a significant positive correlation between the number of CYP2D6*10 alleles and corrected plasma concentrations of S-(+)-MIR. These results yielded the following final model: corrected plasma concentration of S-(+)-MIR=15.9+7.30×(number of CYP2D6*10 alleles) (R=0.279, p=0.023, coefficient of determination (R(2))=0.078). CONCLUSION: Homozygous CYP2D6*10 alleles and smoking have a significant impact on the metabolism of S-(+)-MIR in Japanese patients.

Multiple inductive effects of carbamazepine on combined therapy with paliperidone and amlodipine.

WHAT IS KNOWN AND OBJECTIVE: Carbamazepine is a potent inducer of cytochrome P450 3A and P-glycoprotein. However, there are no reports of the effects of carbamazepine on more than one co-administered drug. CASE SUMMARY: A 53-year-old female patient with schizophrenia and hypertension was on paliperidone 12 mg/day and amlodipine 5 mg/day. When carbamazepine was added to this prescription, the plasma concentrations of both drugs decreased dramatically in a dose-dependent manner. Although the patient's psychotic symptoms did not change, as a result, her mean blood pressure increased to 160·1/103·6 mmHg from 138·4/91·4 mmHg at a carbamazepine dose of 600 mg/day. WHAT IS NEW AND CONCLUSION: Theses cases show the effect of carbamazepine induction on two drugs simultaneously. Care is required when carbamazepine is added to drug regimens including paliperidone or amlodipine alone or together.

Effects of multiple-dose rifampicin 450 mg on the pharmacokinetics of fexofenadine enantiomers in Japanese volunteers.

WHAT IS KNOWN AND OBJECTIVE: Rifampicin is a potent inducer of P-glycoprotein (P-gp) and inhibitor of organic anion-transporting polypeptides (OATPs), with fexofenadine acting as a substrate for both mechanisms. Simultaneous administration of single- or multiple-dose rifampicin 600 mg significantly increases the concentrations of fexofenadine enantiomers by inhibiting OATP transporters. However, the effects of rifampicin 450 mg are unknown. Here, we evaluated the effects of multiple doses of rifampicin 450 mg on the pharmacokinetics of fexofenadine enantiomers in healthy Japanese volunteers. METHODS: In this randomized, two-phase, double-blind crossover study, 10 healthy volunteers received rifampicin 450 mg/day or placebo for 7 days. On day 7, fexofenadine 60 mg was co-administered simultaneously. RESULTS AND DISCUSSION: Rifampicin significantly increased the mean area under the plasma concentration-time curve (AUC) of (R)- and (S)-fexofenadine (3.10-fold and 3.48-fold, respectively) and decreased the renal clearance of (R)- and (S)-fexofenadine (0.40-fold and 0.47-fold, respectively), causing marked differences in the mean amounts of these enantiomers excreted into the urine in the rifampicin phase (P < 0.001). These results indicated that multiple doses of rifampicin 450 mg may be sufficient to inhibit the renal influx transporter and OATP-mediated hepatic uptake of both enantiomers. Moreover, these effects may be greater than the P-gp-inductive effects of rifampicin. Therefore, the interactive mechanism of multidose rifampicin may occur through a combination of OATP and P-gp transporters, thereby altering the pharmacokinetics of fexofenadine enantiomers. WHAT IS NEW AND CONCLUSIONS: In this study of rifampicin 450 mg, the interactive magnitude of the mean AUC values of fexofenadine enantiomers was higher than that observed in the previous study of rifampicin 600 mg, and no dose-dependent inhibitory effects of rifampicin were observed. These effects may be clinically significant in patients receiving fexofenadine and rifampicin.

Clinical response to risperidone in relation to plasma drug concentrations in acutely exacerbated schizophrenic patients.

There are no data indicating a clear relationship between the clinical effect of risperidone and plasma drug concentration. In this study, 51 patients with acutely exacerbated schizophrenia received 6 mg risperidone/day for 4 weeks. A clinical evaluation using the Brief Psychiatric Rating Scale (BPRS) and Udvalg for Klinicke Undersøgelser (UKU) side effect rating scale were performed at baseline and each week. Significant (P < 0.05) correlations were found between plasma concentrations of risperidone and improved total BPRS scores, positive and cognitive symptoms. Plasma concentrations of the active moiety were significantly (P < 0.05) correlated with improved total BPRS scores. Improved score and percent improvement in anxiety-depression subscale were significantly (P < 0.01) correlated with plasma concentrations of the active moiety. The sum of total UKU side effect scores from 1 to 4 weeks was significantly correlated with plasma concentration of both risperidone (rs = 0.319, P < 0.05) and active moiety (rs = 0.373, P < 0.01). The sum of the psychic subgroup scores was significantly correlated with plasma concentrations of active moiety (rs = 0.318, P < 0.05). Results suggest that plasma drug concentrations are, to some extent, associated with improved scores in some psychopathological schizophrenic symptoms and sedative side effects. These findings should be replicated with a larger patient sample.

Intestinal CYP3A4 is not involved in the enantioselective disposition of lansoprazole.

The contribution of (S)-lansoprazole to CYP3A4-catalysed sulfoxidation is greater than that of (R)-lansoprazole. The aim was to investigate the effect of grapefruit juice on the enantioselective disposition of lansoprazole among three CYP2C19 genotype groups. Eighteen healthy subjects, consisting of six each of homozygous extensive metabolizers (homEMs), heterozygous extensive metabolizers (hetEMs) and poor metabolizers (PMs), ingested a single oral dose of 60 mg racemic lansoprazole after taking either 200 ml grapefruit juice or water. There was no effect of grapefruit juice on the mean maximum plasma concentrations (C(max)) or the elimination half-life for each lansoprazole enantiomer in all three CYP2C19 genotype groups. Similarly, the pharmacokinetic parameters of lansoprazole sulfone remained unaltered by grapefruit juice in all three groups. The CYP3A4-mediated first-pass sulfoxidation of (R)- and (S)-lansoprazole were not influenced by grapefruit juice. In addition, stereoselectivity of the intestinal CYP3A4-catalysed sulfoxidation of (R)- and (S)-lansoprazole was not observed.

Pharmacokinetics and pharmacodynamics of etizolam are influenced by polymorphic CYP2C19 activity.

OBJECTIVE: To examine the effect of cytochrome P450 (CYP) 2C19 activity on the single-dose pharmacokinetics and pharmacodynamics of etizolam. METHODS: The subjects were 21 healthy Japanese volunteers. The two mutated alleles (CYP2C19*2 and CYP2C19*3) causing absent CYP2C19 activity were identified by a polymerase chain reaction method. Twelve subjects were extensive metabolizers (EMs) with no or one mutated allele, and nine subjects were poor metabolizers (PMs) with two mutated alleles. The subjects received a single oral 1-mg dose of etizolam, and blood samplings and evaluation of psychomotor function were conducted up to 24 h after dosing. RESULTS: The PMs had significantly larger total area under the plasma concentration-time curve (287+/-74 vs 178+/-122 ng.h/ml, p<0.05) and longer elimination half-life (14.8+/-4.2 vs 10.5+/-3.9 h, p<0.05) of etizolam than the EMs. The area under the score-time curve from 0 to 8 h of the Stanford Sleepiness Scale was significantly larger in the PMs than in EMs (28.9+/-5.2 vs 22.9+/-6.9 score.h, p<0.05). CONCLUSION: The present study suggests that the single-dose pharmacokinetics and pharmacodynamics of etizolam are influenced by polymorphic CYP2C19 activity.

Induction of the metabolism of etizolam by carbamazepine in humans.

OBJECTIVE: To examine the effect of carbamazepine on the single oral dose pharmacokinetics of etizolam. METHODS: Eleven healthy male volunteers received carbamazepine 200 mg/day or placebo for 6 days in a double-blind, randomized, crossover manner, and on the sixth day they received a single oral 1-mg dose of etizolam. Blood samplings and evaluation of psychomotor function by the Digit Symbol Substitution Test and Stanford Sleepiness Scale were conducted up to 24 h after etizolam dosing. Plasma concentration of etizolam was measured using high-performance liquid chromatography. RESULTS: Carbamazepine treatment significantly decreased the peak plasma concentration (17.5+/-4.1 ng/ml versus 13.9+/-4.1 ng/ml; P<0.05), total area under the plasma concentration-time curve (194.8+/-88.9 ng h/ml versus 105.9+/-33.0 ng h/ml; P<0.001), and elimination half-life (11.1+/-4.6 h versus 6.8+/-2.8 h; P<0.01) of etizolam. No significant change was induced by carbamazepine in the two pharmacodynamic parameters. CONCLUSIONS: The present study suggests that carbamazepine induces the metabolism of etizolam.

Pharmacokinetic differences between the enantiomers of lansoprazole and its metabolite, 5-hydroxylansoprazole, in relation to CYP2C19 genotypes.

OBJECTIVE: The purpose of this study was to elucidate the pharmacokinetics of each enantiomer of lansoprazole and 5-hydroxylansoprazole in three different CYP2C19 genotype groups of Japanese subjects. METHODS: Healthy subjects ( n=18), of whom 6 were homozygous extensive metabolizers (homEMs), 6 were heterozygous extensive metabolizers (hetEMs) and 6 were poor metabolizers (PMs), participated in the study. After a single oral dose of 60 mg of racemic lansoprazole, the plasma concentrations of the lansoprazole enantiomers, 5-hydroxylansoprazole enantiomers and lansoprazole sulfone were measured for 24 h post-dose. RESULTS: The plasma concentrations of ( R)-lansoprazole were remarkably higher in all three CYP2C19 genotype groups than those of the corresponding ( S)-enantiomer. The mean maximum plasma concentration ( C(max)) of ( S)-lansoprazole differed significantly among the three groups, whereas there was no difference for the ( R)-enantiomer. The relative area under the plasma concentration (AUC) ratios of ( R)- and ( S)-lansoprazole in the homEMs, hetEMs, and PMs were 1:1.5:4.0 and 1:1.8:7.4, respectively. Yet, the relative AUC ratios of 5-hydroxylansoprazole to lansoprazole for the ( R)- and ( S)-enantiomers in the homEMs, hetEMs, and PMs were almost the same (1:0.73:0.12 and 1:0.77:0.13, respectively). However, the AUC ratios of the ( S)-enantiomer were 13-fold greater for the three CYP2C19 genotypes than those of the corresponding ( R)-enantiomer. CONCLUSIONS: The magnitude of the contribution of CYP2C19 to the 5-hydroxylation of ( S)-lansoprazole was greater than that of the ( R)-enantiomer. The R/S ratios for the AUC of lansoprazole for the homEMs, hetEMs and PMs were 12.7, 8.5 and 5.8, respectively, suggesting a significant effect of CYP2C19 polymorphisms on the stereoselective disposition of lansoprazole.

Inhibition of the metabolism of etizolam by itraconazole in humans: evidence for the involvement of CYP3A4 in etizolam metabolism.

OBJECTIVE: To clarify the involvement of cytochrome P450 (CYP) 3A4 in the metabolism of etizolam. METHODS: The effects of itraconazole, a potent and specific inhibitor of CYP3A4, on the single oral dose pharmacokinetics and pharmacodynamics of etizolam were examined. Twelve healthy male volunteers received itraconazole (200 mg/day) or placebo for 7 days in a double-blind randomized crossover manner, and on the 6th day they received a single oral 1-mg dose of etizolam. Blood samplings and evaluation of psychomotor function using the Digit Symbol Substitution Test and Stanford Sleepiness Scale were conducted up to 24 h after etizolam dosing. Plasma concentration of etizolam was measured by means of high-performance liquid chromatography. RESULTS: Itraconazole treatment significantly increased the total area under the plasma concentration-time curve (AUC; 213+/-106 ng rectangle h/ml versus 326+/-166 ng rectangle h/ml, P<0.001) and the elimination half-life (12.0+/-5.4 h versus 17.3+/-7.4 h, P<0.01) of etizolam. The 90% confidence interval of the itraconazole/placebo ratio of the total AUC was 1.38-1.68, indicating a significant effect of itraconazole. No significant change was induced by itraconazole in the two pharmacodynamic parameters. CONCLUSION: The present study suggests that itraconazole inhibits the metabolism of etizolam, providing evidence that CYP3A4 is at least partly involved in etizolam metabolism.

Association of the TaqI A polymorphism of the dopamine D(2) receptor gene with predisposition to neuroleptic malignant syndrome.

OBJECTIVE: The pathophysiology of neuroleptic malignant syndrome is mainly explained by a central hypodopaminergic state. The familial occurrence of neuroleptic malignant syndrome suggests the involvement of a genetic mechanism in the predisposition to the syndrome. Therefore, the authors examined the association between the TaqI A polymorphism of the dopamine D(2) receptor gene (DRD(2)), which alters DRD(2) density and function, and the development of neuroleptic malignant syndrome. METHOD: The subjects were 15 psychiatric patients who had developed neuroleptic malignant syndrome (12 patients with schizophrenia and three with major depression) and 138 patients with schizophrenia who had never developed neuroleptic malignant syndrome. The TaqI A genotypes, A1 and A2 alleles, were determined by the polymerase chain reaction method. RESULTS: The frequency of the A1 allele was significantly higher in the patients who had developed neuroleptic malignant syndrome (56.8%) than in the patients who had not (35.1%). The proportion of the A1 carrier was significantly higher in the patients with neuroleptic malignant syndrome (14 [93.3%] of 15 patients) than in those without the syndrome (79 [57.2%] of 138 patients). CONCLUSIONS: These findings suggest that the TaqI A DRD(2) polymorphism is associated with the predisposition to neuroleptic malignant syndrome.

No correlations between the urinary ratio of 6beta-hydroxycortisol to free cortisol and pharmacokinetics of alprazolam.

OBJECTIVE: The urinary ratio of 6beta-hydroxycortisol to cortisol is known as a possible marker of CYP3A4 activity. We investigated the correlation between this ratio and the disposition of alprazolam, which is a substrate of CYP3A4. METHODS: Twelve healthy volunteers took a single dose (0.8 mg) of alprazolam at 0800 hours. Blood samplings were conducted up to 48 h after the dosing. Urine was collected during the 24 h prior to dosing. Quantification of alprazolam in plasma and that of cortisol and 6beta-hydroxycortisol in urine was performed using high-performance liquid chromatography. RESULTS: Mean (+/-SD) values of peak plasma concentration (Cmax), time to Cmax (tmax), area under the plasma concentration-time curve [AUC(0-48)] and elimination half-life (tl/2) of alprazolam were 12.0+/-3.0 ng/ml, 1.5+/-0.9 h, 200+/-41 ng/ml h and 16.0+/-4.3 h, respectively. Mean (+/-SD) urinary ratio of 6beta-hydroxycortisol to cortisol was 3.28+/-0.67. No significant correlations were found between urinary ratio of 6beta-hydroxycortisol to cortisol and any pharmacokinetic parameters of alprazolam (Cmax: rs= -0.06; tmax: r(s)= 0.34; AUC(0-48): rs=0.08; t1/2: r(s)= -0.36). CONCLUSION: This study suggests that the urinary ratio of 6beta-hydroxycortisol to cortisol is unlikely to predict pharmacokinetics of alprazolam.

Different enantioselective 9-hydroxylation of risperidone by the two human CYP2D6 and CYP3A4 enzymes.

The antipsychotic agent risperidone, is metabolized by different cytochrome P-450 (CYP) enzymes, including CYP2D6, to the active 9-hydroxyrisperidone, which is the major metabolite in plasma. Two enantiomers, (+)- and (-)-9-hydroxyrisperidone might be formed, and the aim of this study was to evaluate the importance of CYP2D6 and CYP3A4/CYP3A5 in the formation of these two enantiomers in human liver microsomes and in recombinantly expressed enzymes. The enantiomers of 9-hydroxyrisperidone were analyzed with high pressure liquid chromatography using a chiral alpha-1 acid glycoprotein column. A much higher formation rate was observed for (+)-9-hydroxyrisperidone than for (-)-9-hydroxyrisperidone in microsomes prepared from six individual livers. The formation of (+)-9-hydroxyrisperidone was strongly inhibited by quinidine, a potent CYP2D6 inhibitor, whereas ketoconazole, a CYP3A4 inhibitor, strongly inhibited the formation of (-)-9-hydroxyrisperidone. Recombinant human CYP2D6 produced only (+)-9-hydroxyrisperidone, whereas a lower formation rate of both enantiomers was detected with expressed CYP3A4 and CYP3A5. In vivo data from 18 patients during treatment with risperidone indicate that the plasma concentration of the (+)-enantiomer is higher than that of the (-)-enantiomer in extensive metabolizers of CYP2D6. These findings clearly suggest that CYP2D6 plays a predominant role in (+)-9-hydroxylation of risperidone, the major metabolic pathway in clinical conditions, whereas CYP3A catalyzes the formation of the (-)-9-hydroxymetabolite. Further studies are required to evaluate the pharmacological/toxic activity of both enantiomers.

The -141C Ins/Del polymorphism in the dopamine D2 receptor gene promoter region is associated with anxiolytic and antidepressive effects during treatment with dopamine antagonists in schizophrenic patients.

Previous studies have demonstrated a lower density of dopamine D2 receptor (DRD2) in subjects without Del alleles of the -141C Ins/Del polymorphism in DRD2 gene promoter region than in those with one or two Del alleles. The present study aimed to examine whether the -141C Ins/Del DRD2 promoter polymorphism is related to therapeutic response to selective DRD2 antagonists in the treatment of schizophrenia. Subjects consisted of 49 acutely exacerbated schizophrenic inpatients treated with bromperidol (30 cases, mean dose +/- SD: 11.4 +/- 4.8 mg/day) or nemonapride (19 cases, 18 mg/day). Clinical symptoms were evaluated by the Brief Psychiatric Rating Scale (BPRS) before and 3 weeks after the treatment. The -141C Ins/Del DRD2 genotypes, the Ins and Del alleles, were determined by a polymerase chain reaction method. Thirty-five patients were homozygous for the Ins allele and 14 were heterozygous for the Del and Ins alleles. The patients without Del allele showed a higher percentage of improvement in anxiety-depression symptoms than those with Del allele (58.5 +/- 44.5% versus 24.1 +/- 48.2%) after 3 weeks of treatment while percentage improvement in total BPRS or other subgrouped symptoms (positive, negative, excitement and cognitive symptoms) was similar between the two genotype groups. The present results suggest that the -141C Ins/Del DRD2 polymorphism is associated with anxiolytic and antidepressive effects of neuroleptic treatment in schizophrenic patients.

Effects of genetic polymorphism of CYP1A2 inducibility on the steady-state plasma concentrations of trazodone and its active metabolite m-chlorophenylpiperazine in depressed Japanese patients.

The effects of a genetic polymorphism of inducibility of cytochrome P450 (CYP) 1A2 on the steady-state plasma concentrations of trazodone and its active metabolite, m-chlorophenylpiperazine, were studied in order to clarify if these steady-state plasma concentrations are dependent on the CYP1A2 polymorphism. Fifty-eight Japanese depressed patients received trazodone 150 mg/day at bedtime. The steady-state plasma concentrations of trazodone and m-chlorophenylpiperazine were measured in duplicate using high performance liquid chromatographic method, and were corrected to the mean body weight for analyses. A point mutation from guanine (wild type) to adenine (mutated type) at position -2964 in the 5'-flanking region of CYP1A2 gene was identified by polymerase chain reaction fragment length polymorphism method. The mean steady-state plasma concentration of trazodone, but not m-chlorophenylpiperazine was significantly (P<0.05) lower in smokers than in non-smokers. Twenty-two smokers had 16 homozygotes of the wild type allele, 5 heterozygotes of the wild type and mutated alleles, and one homozygote of the mutated allele. There was no significant difference in the mean steady-state plasma concentration of trazodone or m-chlorophenylpiperazine between smokers with no mutation and those with mutation, although one homozygote of the mutated allele had the highest steady-state plasma concentration of trazodone in smokers. The present study thus suggests that CYP1A2 polymorphism does not necessarily have predictive value of the steady-state plasma concentration of trazodone or m-chlorophenylpiperazine in most of the smokers treated with trazodone.

Association between TaqI A dopamine D2 receptor polymorphism and therapeutic response to bromperidol: a preliminary report.

The relationship between TaqI A dopamine D2 receptor (DRD2) polymorphism and therapeutic response to bromperidol, a selective dopamine antagonist, was investigated in 30 acutely exacerbated schizophrenic inpatients. Patients were treated with bromperidol 6-18 mg/day for 3 weeks. Clinical symptoms were evaluated by the Brief Psychiatric Rating Scale (BPRS) before and 3 weeks after the treatment. The TaqI A genotypes were determined with the PCR method. There was no significant difference in the percentage improvement of total BPRS or 5-subgrouped symptoms (positive, negative, anxiety-depression, excitement and cognitive symptoms) after the 3-week treatment between the patients with A1 alleles (n=18) and those with no A1 allele (n=12). Although the present study is preliminary, it is suggested that the TaqI A DRD2 polymorphism is not associated with therapeutic response to bromperidol in schizophrenic patients.

Relationship between Taq1 A dopamine D2 receptor (DRD2) polymorphism and prolactin response to bromperidol.

The dopamine D2 receptor (DRD2) gene has a Taq1 A restriction fragment length polymorphism yielding two alleles, A1 and A2. We have previously shown that female patients with the A1 allele show greater prolactin response to nemonapride, a selective antagonist for D2-like dopamine receptors, in schizophrenic patients. In the present study, the relationship between this polymorphism and prolactin response to bromperidol was investigated in 32 untreated schizophrenic inpatients (16 males, 16 females). The daily dose of bromperidol was fixed at 6 (n = 10), 12 (n = 13), or 18 mg (n = 9) during a 2-week treatment period. Taq1 A genotypes were determined by PCR method. Plasma prolactin concentration was measured by radioimmunoassay. Plasma concentration of bromperidol was measured by HPLC method. The subjects were divided into four subgroups by gender and the genotypes, i.e., 10 males and 11 females with the A1 allele, 6 males and 5 females with no A1 allele. The females with the A1 allele had the highest Delta prolactin (the change from the pretreatment concentration)/bromperidol concentration ratio among the other groups (P < 0.05). The present study thus suggests that female patients with the A1 allele show greater prolactin response to bromperidol, who may have a high risk for adverse effects associated with neuroleptic-induced hyperprolactinemia.