Application of plasma levels of olanzapine and N-desmethyl-olanzapine to monitor metabolic parameters in patients with schizophrenia.

Metabolic disturbance is a common side effect of olanzapine (OLZ); however, the relationships between plasma OLZ concentration (COLZ) and metabolic disturbance remain unclear. Our previous study revealed that COLZ≧22.77ng/mL was a positive predictor of therapeutic efficacy in patients with schizophrenia. This study aimed to investigate the roles of OLZ or N-desmethyl-olanzapine (DMO) in metabolic outcomes among OLZ-treated patients with schizophrenia. The metabolic syndrome (MS) was diagnosed based on the modified the National Cholesterol Education Program Adult Treatment Panel III criteria for Asians. HPLC-ECD analytical system was applied to determine the COLZ and DMO concentration (CDMO). The absolute drug levels and concentration-to-dose ratios (C/D ratios) were tested for their correlations to metabolic parameters. Total 151 fasting blood samples from patients with schizophrenia were collected. DMO C/D ratio negatively correlated with weight, body mass index, waist circumference, and C-peptide level. The receiver operator characteristic analysis determined a threshold CDMO>5.63ng/mL and DMO C/D ratio>0.35ng/mL/mg were negative predictors of MS. The COLZ/CDMO ratio>6.03 was identified as positive predictor of MS. Combined with previous study result, we proposed that the optimal OLZ treatment should maintain COLZ/CDMO ratio between 3 and 6 to maximize the clinical efficacy and minimize the metabolic side effects. Our findings suggested that therapeutic drug monitoring on OLZ and DMO is a valuable tool to monitor metabolic side effects in OLZ-treated patients with schizophrenia.

Application of Plasma Levels of Olanzapine and N-Desmethyl-Olanzapine to Monitor Clinical Efficacy in Patients with Schizophrenia.

BACKGROUND: This therapeutic drug monitoring (TDM) study aimed to determine the role of olanzapine (OLZ) and N-desmethyl-OLZ (DMO) levels in the therapeutic efficacy of OLZ in patients with schizophrenia. METHOD: Plasma concentrations of OLZ (COLZ) and DMO (CDMO) in schizophrenic patients 12 hours post-dose were assessed. The correlations of COLZ and CDMO with the various scores of the Positive and Negative Syndrome Scale (PANSS) were evaluated. A receiver operating characteristic curve (ROC) was utilized to identify the threshold COLZ and COLZ/CDMO ratio for maintenance of satisfactory efficacy. RESULTS: A total of 151 samples from patients with schizophrenia were analyzed for individual COLZ and CDMO levels. The mean COLZ and CDMO levels were 37.0 ± 25.6 and 6.9 ± 4.7 ng/mL, respectively, and COLZ was ~50% higher in female or nonsmokers (p<0.01). In all patients, the daily dose of OLZ was positively correlated with COLZ and CDMO. Linear relationships between COLZ and OLZ dose were observed in both nonsmokers and smokers (rs = 0.306, 0.426, p<0.01), although CDMO was only correlated with OLZ dose in smokers (rs = 0.485, p<0.01) and not nonsmokers. In all patients, COLZ was marginally negatively correlated with the total PANSS score. The total PANSS score was significantly negatively correlated with the COLZ/CDMO ratio (p<0.005), except in smokers. The ROC analysis identified a COLZ/CDMO ratio ≥2.99 or COLZ ≥22.77 ng/mL as a predictor of maintenance of an at least mildly ill status (PANSS score ≤58) of schizophrenia in all patients. CONCLUSIONS: A significantly negative correlation between the steady-state COLZ/CDMO ratio and total PANSS score was observed in Taiwanese schizophrenic patients. TDM of both OLZ and DMO levels could assist clinical practice when individualizing OLZ dosage adjustments for patients with schizophrenia.

Carnosine ameliorates lens protein turbidity formations by inhibiting calpain proteolysis and ultraviolet C-induced degradation.

Carnosine (CAR) is an endogenous peptide and present in lens, but there is little evidence for its effectiveness in calpain-induced proteolysis inhibition and its differential effects toward different wavelengths of ultraviolet (UV) irradiation. This study aimed to develop three in vitro cataract models to compare the mechanisms underlying the protective activities of CAR. Crude crystallins extracted from porcine lenses were used for antiproteolysis assays, and purified γ-crystallins were used for anti-UV assays. The turbidity in those in vitro models mimics cataract formation and was assayed by measuring optical density (OD) at 405 nm. The effectiveness of CAR on calpain-induced proteolysis was studied at 37 and 58 °C. Patterns of proteins were then analyzed by SDS-PAGE. The turbidity was reduced significantly (p<0.05) at 60 min measurements with the increased concentration of CAR (10-300 mM). SDS-PAGE showed that the decreased intensities at both ∼28 and ∼30 kDa protein bands in heat-enhanced assays were ameliorated by CAR at ≥10 mM concentrations. In UV-B studies, CAR (200, 300 mM) reduced the turbidity of γ-crystallin significantly (p<0.05) at 6 h observations. The turbidity of samples containing γ-crystallins was ameliorated while incubated with CAR (100, 300 mM) significantly (p<0.05) following 4 h of exposure to UV-C. SDS-PAGE showed that the presence of CAR reduced UV-B-induced aggregation of γ-crystallins at ∼44 kDa and resulted in less loss of γ-crystallin following UV-C exposure. The result of modeling also suggests that CAR acts as an inhibitor of calpain. In conclusion, CAR protects lens proteins more readily by inhibiting proteolysis and UV-C-induced degradation than aggregation induced by UV-B irradiation.