Effects of Oral Nutritional Supplement with ß-Hydroxy-ß-methylbutyrate (HMB) on Biochemical and Hematological Indices in Community-Dwelling Older Adults at Risk of Malnutrition: Findings from the SHIELD Study.

Malnutrition may result in abnormal biochemical and hematological indices. This planned prespecified analysis investigated the effects of a specialized oral nutritional supplement (ONS) on biochemical and hematological indices in community-dwelling older adults at risk of malnutrition. In the Strengthening Health in ELDerly through nutrition (SHIELD) study, 811 older adults aged 65 years and above took part in this randomized, double-blind, placebo-controlled, multi-center study. Participants were randomly allocated to either a complete and balanced specialized ONS (each serving provides 262 kcal, 10.5 g protein, 7.75 µg vitamin D3, and 0.74 g calcium ß-hydroxy-ß-methylbutyrate) and dietary counselling (intervention group) or a placebo and dietary counselling (placebo group). Both groups consumed study products twice a day for 180 days. Data were collected at baseline, day 90, and day 180. Blood analysis results at follow-up visits were analyzed using repeated measures analysis of covariance with adjustments for confounders. Overall, when compared with the placebo group, the intervention group showed significantly greater urea (6.0 mmol/L vs. 5.4 mmol/L, p < 0.001), urea to creatinine ratio (4.39 vs. 4.26, p < 0.001), prealbumin (24.9 mg/dL vs. 24.0 mg/dL, p < 0.001), vitamin B12 (480.0 pmol/L vs. 420.1 pmol/L, p < 0.001), and globulin levels (26.8 g/L vs. 26.5 g/L, p = 0.032). The intervention group also had a significantly higher absolute reticulocyte count (62.0 × 103/µL vs. 58.2 × 103/µL, overall p < 0.001) and mean platelet volume (10.0 fL vs. 9.9 fL, overall p = 0.003). Furthermore, significant improvements were seen in total protein at day 90 (71.7 g/L vs. 71.1 g/L, p = 0.017) and in absolute monocyte count at day 90 (0.50 × 103/µL vs. 0.47 × 103/µL, p = 0.009) in the intervention group. In conclusion, daily consumption of a specialized ONS for six months led to significant improvements in biochemical and hematological indices in community-dwelling older adults at risk of malnutrition.

Dried Blood Spots as Matrix for Evaluation of Valproate Levels and the Immediate and Delayed Metabolomic Changes Induced by Single Valproate Dose Treatment.

The immediate and delayed metabolic changes in rats treated with valproate (VPA), a drug used for the treatment of epilepsy, were profiled. An established approach using dried blood spots (DBS) as sample matrices for gas chromatography/mass spectrometry-based metabolomics profiling was modified using double solvents in the extraction of analytes. With the modified method, some of the previously undetectable metabolites were recovered and subtle differences in the metabolic changes upon exposure to a single dose of VPA between males and female rats were identified. In male rats, changes in 2-hydroxybutyric acid, pipecolic acid, tetratriacontane and stearic acid were found between the control and treatment groups at various time points from 2.5 h up to 24 h. In contrast, such differences were not observed in female rats, which could be caused by the vast inter-individual variations in metabolite levels within the female group. Based on the measured DBS drug concentrations, clearance and apparent volume of distribution of VPA were estimated and the values were found to be comparable to those estimated previously from full blood drug concentrations. The current study indicated that DBS is a powerful tool to monitor drug levels and metabolic changes in response to drug treatment.

Evaluating the Relationship between Vancomycin Trough Concentration and 24-Hour Area under the Concentration-Time Curve in Neonates.

Bacterial sepsis is a major cause of morbidity and mortality in neonates, especially those involving methicillin-resistant Staphylococcus aureus (MRSA). Guidelines by the Infectious Diseases Society of America recommend the vancomycin 24-h area under the concentration-time curve to MIC ratio (AUC24/MIC) of >400 as the best predictor of successful treatment against MRSA infections when the MIC is ≤1 mg/liter. The relationship between steady-state vancomycin trough concentrations and AUC24 values (mg·h/liter) has not been studied in an Asian neonatal population. We conducted a retrospective chart review in Singapore hospitals and collected patient characteristics and therapeutic drug monitoring data from neonates on vancomycin therapy over a 5-year period. A one-compartment population pharmacokinetic model was built from the collected data, internally validated, and then used to assess the relationship between steady-state trough concentrations and AUC24 A Monte Carlo simulation sensitivity analysis was also conducted. A total of 76 neonates with 429 vancomycin concentrations were included for analysis. Median (interquartile range) was 30 weeks (28 to 36 weeks) for postmenstrual age (PMA) and 1,043 g (811 to 1,919 g) for weight at the initiation of treatment. Vancomycin clearance was predicted by weight, PMA, and serum creatinine. For MRSA isolates with a vancomycin MIC of ≤1, our major finding was that the minimum steady-state trough concentration range predictive of achieving an AUC24/MIC of >400 was 8 to 8.9 mg/liter. Steady-state troughs within 15 to 20 mg/liter are unlikely to be necessary to achieve an AUC24/MIC of >400, whereas troughs within 10 to 14.9 mg/liter may be more appropriate.

Clinical validation and implications of dried blood spot sampling of carbamazepine, valproic acid and phenytoin in patients with epilepsy.

To facilitate therapeutic monitoring of antiepileptic drugs (AEDs) by healthcare professionals for patients with epilepsy (PWE), we applied a GC-MS assay to measure three AEDs: carbamazepine (CBZ), phenytoin (PHT) and valproic acid (VPA) levels concurrently in one dried blood spot (DBS), and validated the DBS-measured levels to their plasma levels. 169 PWE on either mono- or polytherapy of CBZ, PHT or/and VPA were included. One DBS, containing ∼15 µL of blood, was acquired for the simultaneous measurement of the drug levels using GC-MS. Simple Deming regressions were performed to correlate the DBS levels with the plasma levels determined by the conventional immunoturbimetric assay in clinical practice. Statistical analyses of the results were done using MedCalc Version 12.6.1.0 and SPSS 21. DBS concentrations (Cdbs) were well-correlated to the plasma concentrations (Cplasma): r=0.8381, 0.9305 and 0.8531 for CBZ, PHT and VPA respectively, The conversion formulas from Cdbs to plasma concentrations were [0.89×CdbsCBZ+1.00]µg/mL, [1.11×CdbsPHT-1.00]µg/mL and [0.92×CdbsVPA+12.48]µg/mL respectively. Inclusion of the red blood cells (RBC)/plasma partition ratio (K) and the individual hematocrit levels in the estimation of the theoretical Cplasma from Cdbs of PHT and VPA further improved the identity between the observed and the estimated theoretical Cplasma. Bland-Altman plots indicated that the theoretical and observed Cplasma of PHT and VPA agreed well, and >93.0% of concentrations was within 95% CI (±2SD); and similar agreement (1∶1) was also found between the observed Cdbs and Cplasma of CBZ. As the Cplasma of CBZ, PHT and VPA can be accurately estimated from their Cdbs, DBS can therefore be used for drug monitoring in PWE on any of these AEDs.

Prevalence of drug resistant epilepsy in adults with epilepsy attending a neurology clinic of a tertiary referral hospital in Singapore.

PURPOSE: To determine the proportion of population of adult people with epilepsy (PWE) in Singapore, who suffer from drug resistant epilepsy (DRE). METHODS: All adult PWE who had attended the neurology specialist clinic of a tertiary referral hospital in Singapore were profiled for drug responses according to the definition for DRE as specified by the International League against Epilepsy (ILAE) 2010 consensus. This is a retrospective cohort study. Data collected included demographics, characteristics of seizure and epilepsy, blood biochemistry levels, electroencephalogram and brain imaging findings, and medication histories. The types and dosages of antiepileptic drugs (AEDs) used were retrieved from case notes and checked against pharmacy records. Each patient was counselled upon the diagnosis of epilepsy and taught to maintain a seizure diary. The dates and number of seizures were retrieved from these diaries at each visit. Treatment-related adverse effects were routinely assessed and hence, patients were assumed to not have treatment-related adverse effects when no relevant documentation was encountered. RESULTS: The prevalence rate of DRE in this clinic was 21.5%, while 40.9% of PWE were drug responsive/seizure free at the point prevalence day (n=557). From multivariate analysis, patients with structural-metabolic aetiology [odds ratio (OR) 1.78, 95% confidence interval (CI) 1.003-3.148], mental retardation [OR 2.51, 95% CI 1.073-5.863], psychiatric illnesses [OR 3.349, 95% CI 1.181-9.501] and pre-treatment seizure frequency of more than once monthly [OR 2.775, 95% CI 1.190-6.469] were found to be more likely to have DRE (p≤0.05). Although the influence of Indian ethnicity on the risk of DRE was only found in the univariate analysis, it warrants investigation in a larger cohort. CONCLUSION: The findings may aid policy makers in designing treatment guidelines and allocating resources around PWE, with careful considerations that at any given time, 1 in 5 PWE have DRE.

Estimation and comparison of carbamazepine population pharmacokinetics using dried blood spot and plasma concentrations from people with epilepsy: the clinical implication.

To establish using dried blood spot (DBS) as a surrogate to plasma for therapeutic drug monitoring (TDM) of carbamazepine (CBZ), we compared the population pharmacokinetic (PPK) estimates from concurrent DBS and plasma levels. The dose-concentration relationship, estimated parameter and variability were determined. A total of 98 observations from 97 people with epilepsy (PWE) were included in this study. Data was split into 3:1 ratio for the respective index group and validation group. Non-linear mixed effects regression with one compartment, first order absorption and elimination model was utilized. Covariates were screened for inclusion into final model via forward stepwise addition and backward elimination method. Predictive performances of the final models were assessed for bias and precision. The typical clearance for CBZ was estimated to be 5.85 and 5.68 L/h from plasma and DBS concentrations, respectively. The final models for clearance estimates obtained from plasma concentrations (Cplasma ) included total daily CBZ dose per unit weight (DD) and sex while from DBS concentrations (Cdbs ) included only DD. The final models were both precise and non-bias. The developed PPK models had comparable estimates, errors and predictive performances. Our findings suggest that Cplasma and Cdbs could be used interchangeably for pharmacokinetic studies of CBZ.

A simple assay for determination of levetiracetam in rat dried blood spots by LC-MS/MS.

BACKGROUND: A simple LC-MS/MS method was developed and validated for the quantification of levetiracetam (LEV, Keppra®), a broad-spectrum antiepileptic drug (AED) in rat dried blood spots (DBS). LEV was simply extracted with methanol spiked with adenosine (ADE) as IS before LC-MS/MS analysis. The correlation between the DBS and plasma concentrations of LEV was also determined. RESULTS: Linearity was from 0.067-60 µg/ml for LEV in DBS samples. The intra- and inter-day accuracy and precision of the assay met validation acceptance criteria. The developed assay was applied to monitor levetiracetam DBS levels in Sprague-Dawley rats after intravenous administration. DBS concentrations were well correlated to the plasma concentrations (R² = 0.9399), as fraction of LEV bound to blood cells remains very constant (0.466 ± 0.041) over a wide concentration range. CONCLUSION: The study illustrated that DBS could be used as alternative matrix for monitoring LEV in preclinical studies.

Developing a nomogram for dose individualization of phenytoin in Asian pediatric patients derived from population pharmacokinetic modeling of saturable pharmacokinetic profiles of the drug.

BACKGROUND: A population pharmacokinetic model for phenytoin in Asian pediatric patients was developed to determine the influence of concurrent medications, patient demographics, and blood biochemistry on the pharmacokinetic profile of phenytoin. METHODS: Retrospective clinical data were obtained from 66 patients (age, 1-16 years) for the determination of pharmacokinetic parameters of phenytoin using WinNonmix. Data from 49 patients (74.2%) were allocated in the "index" group, and the other 17 patients (25.8%) in the "validation" group. Models were compared by final log likelihood, mean error as a measure of bias, and root-mean-squared error as a measure of precision. RESULTS: The Michaelis-Menten constant (km) and volume of distribution (V) were fixed at 9.08 mg/L and 1.23 L/kg, respectively. The saturated elimination rate (V × Vmax) of phenytoin was then found to be 0.525 mg/kg per hour (352.9 4 mg/d for a 28.0 kg individual). Patients' body surface area (in square meter) and catalytic activities of liver enzymes aspartate aminotransferase (U/L) and alkaline phosphatase (U/L) appeared to have significant correlation with Vmax, whereas coadministrating drugs with phenytoin did not yield any significant effect. The final model for the saturated elimination rate was (Equation is included in full-text article.) In validation of the final model, the mean error was found to be -0.805 (95% confidence interval, -3.67 to 2.06), and the root-mean-squared error was 7.92 (95% confidence interval, 3.41-12.43). CONCLUSIONS: The obtained results indicated the need to consider patients' body surface area and the catalytic activities of liver enzymes aspartate aminotransferase and alkaline phosphatase when dosing phenytoin. Based on the population pharmacokinetic parameters, a nomogram was subsequently developed for dose individualization of phenytoin in Asian pediatric patients.

A retrospective study on the usage of antiepileptic drugs in Asian children from 2000 to 2009 in the largest pediatric hospital in Singapore.

PURPOSE: In light of the increasing usage of the newer antiepileptic drugs (AEDs) in other countries, we reviewed the prescribing pattern of AEDs in Singapore over the last 10 years (2000-2009). METHODS: A retrospective review of pharmacy dispensing records solicited from the only children's hospital in Singapore was performed to analyze the trend in AEDs prescribing in the last 10 years. We also examined the correlation between the serum concentrations of valproic acid (VPA), the most-prescribed AED, and seizure control. Descriptive and inferential statistical analyses were then performed on the findings. RESULTS: A total of 41 671 prescriptions on AEDs were retrieved and analyzed. Despite the introduction of the second-generation AEDs, the first generation AEDs still dominate epilepsy treatment in Asian children, with VPA being the mostly prescribed AED (about 40% of the total AEDs usage). The majority of patients (62.8%) were on monotherapy. The mean VPA serum concentration in patients with good seizure control was 68.6 µg/ml (SD = 26.4 µg/ml; range = 12.2-138.0 µg/ml), which was statistically higher than the mean VPA concentration of 57.7 µg/ml (SD = 27.1 µg/ml; range = 11.1-149.0 µg/ml) in patients with poor seizure control (p < 0.0001). CONCLUSION: With VPA being the most prescribed AED in our clinical practice, and the finding in this study that with careful classification of the patients' condition, serum concentrations of VPA generally correlate well with the seizure control, the correct dose titration of VPA with therapeutic drug monitoring is still of paramount importance.

Evaluation of dried blood spots as sample matrix for gas chromatography/mass spectrometry based metabolomic profiling.

We propose using dried blood spots (DBS) as sample matrix for gas chromatography/mass spectrometry (GC/MS) based metabolomic profiling for the benefits of higher sample stability, more convenient sample acquisition with DBS, higher analyte separation power, and more readily biomarker identification with GC/MS. To establish this proposition, the metabolomic profiles generated from DBS were compared with that obtained from the conventional whole blood and plasma matrixes and also with dried plasma spots (DPS) as another covariate control. Our findings indicated that whole blood produced the most number of detectable markers (866), whereas DPS yielded the least number (614). DBS and plasma matrix, on the other hand, produced the most similar numbers of detectable (695 vs 749) and identifiable markers (137 vs 147, matching with Fiehn library). From the analysis of the DBS and plasma metabolomic profiles, it was concluded that when l-lysine 2, iminodiacetic acid 2, dl-threo-beta-hydroxyaspartic acid, citric acid, or adenosine-5-monophosphate 2 are not involved as markers, DBS could be a suitable substitute for plasma for metabolomic profiling.