Tardive dyskinesia in CYP2D6 polymorphism in Chinese

Efficacy, acceptability and tolerability of 8 atypical antipsychotics in Chinese patients with acute schizophrenia: A network meta-analysis

OBJECTIVE

We aimed to create hierarchies of the efficacy, acceptability and tolerability of eight atypical antipsychotics in the treatment of Chinese patients with acute schizophrenia.

METHOD

We systematically searched for RCT articles published between January 1st 2005 and December 31st 2014 in electronic databases (Medline, Pubmed, Embase, the Cochrane Library and ClinicalTrial.gov for studies in English and the China National Knowledge Infrastructure, Wan Fang, and VIP Information/Chinese Scientific Journals Database for studies in Chinese). The primary outcome was efficacy, as measured by the change of PANSS total score. Pairwise comparisons were performed using random-effects model by the Dersimonian-Laird method and network meta-analyses were performed in a Bayesian set.

RESULTS

Sixty high-quality RCTs with 6418 participants were included. A pattern of superiority from olanzapine, paliperidone and amisulpride was seen in the primary outcome. Only paliperidone was found better than aripiprazole (odds ratio, 0.49 [95% credible intervals, 0.25 to 0.99]), ziprasidone (0.42 [0.21 to 0.85]) and quetiapine (0.36 [0.13 to 0.93]) in terms of all-cause discontinuation. The best and worst drugs in terms of weight gain, EPS and somnolence were aripiprazole and olanzapine, clozapine and amisulpride, aripiprazole and clozapine, respectively. The rank of efficacy did not change substantially in sensitivity analyses or in meta-regressions.

CONCLUSION

Our findings provided the hierarchies of eight antipsychotics in efficacy, acceptability and tolerability. These findings are expected to help Chinese clinicians to select the appropriate antipsychotic drug for their patients.

CYP450 pharmacogenetic treatment strategies for antipsychotics: a review of the evidence

Although a number of first- and second-generation antipsychotics are available, achieving optimal therapeutic response for patients with schizophrenia can be challenging. The presence of polymorphic alleles for cytochrome P (CYP) 450 may result in lack of expression, altered levels of expression, or altered function of CYP450 enzymes. CYP2D6, CYP1A2, and CYP3A4/5 are major enzymes in the metabolism of antipsychotics and polymorphisms of alleles for these proteins are associated with altered plasma levels. Consequently, standard dosing may result in drug plasma concentrations that are subtherapeutic or toxic in some patients. Patient CYP450 genotype testing can predict altered pharmacokinetics, and is currently available and relatively inexpensive. Evidence-based guidelines provide dose recommendations for some antipsychotics. To date few studies have demonstrated a significant association with genotype-guided antipsychotic use and clinical efficacy. However, many studies have been small, retrospective or cohort designs, and many have not been adequately powered. Numerous studies have shown a significant association between genotype and adverse effects, such as CYP2D6 polymorphisms and tardive dyskinesia. This review summarizes evidence for the role of CYP450 genetic variants in the response to antipsychotic medications and the clinical implications of pharmacogenetics in the management of patients with schizophrenia.

Tardive dyskinesia in Chinese inpatients with chronic schizophrenia

The objective of the study was to determine the point prevalence of tardive dyskinesia (TD) in Chinese inpatients with chronic schizophrenia and its association with sociodemographic, clinical and treatment variables and other movement disorders. A cross-sectional assessment of a randomly selected cohort of inpatients (n=225; mean age=42+/-7 years) with DSM-IV schizophrenia was employed using standard rating instruments for TD and other drug-induced movement disorders, in addition to catatonia, and psychotic, negative, depressive and obsessive-compulsive symptoms. Using Schooler and Kane's criteria, 15 subjects (6.7%) had TD. Patients with TD were significantly older and significantly fewer of them were taking antiparkinsonian medication than subjects without TD. There was no significant difference between the TD and non-TD groups with respect to other demographic, clinical and treatment variables including sex, age of onset, length of contact with psychiatric services, current antipsychotic dosage, negative symptoms, catatonia and parkinsonism. The results confirmed the low prevalence of TD in patients with chronic schizophrenia compared to those found in Caucasian patients. The study has also replicated the association of TD in Chinese schizophrenia patients with older age but failed to demonstrate any association between TD and other demographic or clinical characteristics including catatonia.

Genetic association analysis between CYP2D6*2 allele and tardive dyskinesia in schizophrenic patients

Previous studies have shown a possible association between tardive dyskinesia (TD) and debrisoquine 4-hydroxylase (CYP2D6) polymorphisms, which result in absent enzyme activity. We have recently found a positive association between TD and the CYP2D6*10 allele, which codes for the intermediate metabolizer (IM) phenotype and is characterized by decreased but not absent CYP2D6 activity in Japanese schizophrenic patients. In addition, the CYP2D6* 2 allele with the HhaI site mutation in exon 6 has also been reported to be an IM allele and a risk factor for Parkinson's disease (PD) in the Japanese population. In the present study, we investigated potential contributions of the CYP2D6*2 allele to TD using case-control and regression analysis in 99 schizophrenic patients. No significant differences in genotypic and allelic frequencies were found between patients with and without TD. Even after using regression analysis to adjust for the confounding variables, there was no significant association of the CYP2D6*2 genotype with either outcome variable, the occurrence of TD or the total AIMS score. These results suggest that the CYP2D6*2 allele may not contribute to the pathogenesis of TD.