Ethnic or Racial Differences Revisited

Population Pharmacokinetic Analysis of Doripenem after Intravenous Infusion in Korean Patients with Acute Infections

We investigated the population pharmacokinetics (PK) of doripenem in Korean patients with acute infections and determined an appropriate dosing regimen using a Monte Carlo simulation for predicting pharmacodynamics (PD). Patients (n = 37) with a creatinine clearance (CL_CR) of 20 to 50 ml/min or >50 ml/min who received a 250-mg or 500-mg dose of doripenem over the course of 1 h every 8 h, respectively, were included in this study. Blood samples were taken predosing and 0 h, 0.5 h, and 4 to 6 h after the fourth infusion. A nonlinear mixed-effect modeling tool was used for the PK analysis and pharmacodynamic simulation; doripenem PK were well described by a one-compartment model. The population mean values of the body weight (WT)-normalized clearance (CL/WT) and the body weight-normalized volume of distribution (V/WT) were 0.109 liter/h/kg of body weight (relative standard error, 9.197%) and 0.280 liter/kg (relative standard error, 9.56%), respectively. Doripenem CL was significantly influenced by CL_CR The proposed equation to estimate doripenem CL in Korean patients was CL/WT = 0.109 × WT × (CL_CR/57)^0.688, where CL/WT is in liters per hour per kilogram. CL in Korean patients was expected to be lower than that in Caucasian patients, regardless of renal function. The Monte Carlo simulation showed that 90% attainment of target PK/PD magnitudes could be achieved with the usual dosing regimens when the MIC was ≤1 mg/liter. However, prolonged infusions (4 h) should be considered, especially when patients have augmented renal function and for patients infected with pathogens with a high MIC. Our results provide an individualized doripenem dosing regimen for patients with various renal functions and for patients infected with bacteria with decreased susceptibility.

Research Professionals' Perspectives, Barriers, and Recommendations Regarding Minority Participation in Clinical Trials

OBJECTIVE

This study aims to investigate research professionals' perspectives regarding minority participation in clinical trials.

METHODS

A web-based survey of research professionals at US institutions receiving NIH and/or AHRQ funding to conduct clinical research in 2013. Descriptive statistics, mean, standard deviation (SD), and the Wilcoxon rank-sum test were utilized for analysis.

RESULTS

Distributed were 13,041 surveys with 967 (7.4%) responses. Overall and race-stratified analyses included 633 and 521 surveys, respectively. A majority agreed that patients' race (mean, 3.4; SD = 1.0) and primary language (mean, 4.0; SD = 0.9) have an effect on enrollment. They had more success in enrolling those whose primary language was the same as their own (mean, 3.8; SD = 1.0), and that a language barrier and time spent arranging for interpreters had prevented them from offering a study to potential candidates (mean, 3.2; SD = 1.2). Non-Caucasian respondents were more likely to agree that "fear of unknown side effects" was a deterrent for minorities (p < 0.01), "minorities are more likely to be unavailable for follow-up phone calls" (p = 0.07), and "the unavailability of translated material discourages non-English speakers from participation" (p = 0.08). They also were more likely to be neutral or agree with being discouraged from enrolling minorities because of the possibility of their withdrawal or being less likely to be available for phone follow-ups and follow-up visits (all p < 0.01).

CONCLUSION

Despite a few subtle racial differences in research professionals' perspectives, a majority expressed no hesitation in enrolling minorities. Patients' race and primary language appeared to influence enrollment. A language barrier appeared to be the strongest barrier for research professionals.

Inter-rater variability of visual interpretation and comparison with quantitative evaluation of 11C-PiB PET amyloid images of the Japanese Alzheimer's Disease Neuroimaging Initiative (J-ADNI) multicenter study

PURPOSE

The aim of this study was to assess the inter-rater variability of the visual interpretation of ¹¹C-PiB PET images regarding the positivity/negativity of amyloid deposition that were obtained in a multicenter clinical research project, Japanese Alzheimer's Disease Neuroimaging Initiative (J-ADNI). The results of visual interpretation were also compared with a semi-automatic quantitative analysis using mean cortical standardized uptake value ratio to the cerebellar cortex (mcSUVR).

METHODS

A total of 162 ¹¹C-PiB PET scans, including 45 mild Alzheimer's disease, 60 mild cognitive impairment, and 57 normal cognitive control cases that had been acquired as J-ADNI baseline scans were analyzed. Based on visual interpretation by three independent raters followed by consensus read, each case was classified into positive, equivocal, and negative deposition (ternary criteria) and further dichotomized by merging the former two (binary criteria).

RESULTS

Complete agreement of visual interpretation by the three raters was observed for 91.3% of the cases (Cohen κ = 0.88 on average) in ternary criteria and for 92.3% (κ = 0.89) in binary criteria. Cases that were interpreted as visually positive in the consensus read showed significantly higher mcSUVR than those visually negative (2.21 ± 0.37 vs. 1.27 ± 0.09, p < 0.001), and positive or negative decision by visual interpretation was dichotomized by a cut-off value of mcSUVR = 1.5. Significant positive/negative associations were observed between mcSUVR and the number of raters who evaluated as positive (ρ = 0.87, p < 0.0001) and negative (ρ = -0.85, p < 0.0001) interpretation. Cases of disagreement among raters showed generally low mcSUVR.

CONCLUSIONS

Inter-rater agreement was almost perfect in ¹¹C-PiB PET scans. Positive or negative decision by visual interpretation was dichotomized by a cut-off value of mcSUVR = 1.5. As some cases of disagreement among raters tended to show low mcSUVR, referring to quantitative method may facilitate correct diagnosis when evaluating images of low amyloid deposition.

Population Pharmacokinetic Analysis of Piperacillin/Tazobactam in Korean Patients with Acute Infections

Background

For more effective and safer usage of antibiotics, the dosing strategy should be individualized based on the patients’ characteristics, including race. The aim of this study was to investigate the population pharmacokinetic (PK) profiles of piperacillin and tazobactam in Korean patients with acute infections.

Materials and Methods

At least four consecutive 2/0.25 g or 4/0.5 g doses of piperacillin/tazobactam (TZP) were intravenously infused over 1 h every 8 h for patients with creatinine clearance (CL_cr) ≤50 ml/min or CL_cr >50 mL/min, respectively. Blood samples from 33 patients at a steady-state were taken pre-dose and at 0 min, 30 min, and 4-6 h after the fourth infusion. The population PK analysis was conducted using a non-linear mixed-effects method. A likelihood ratio test was used to select significant covariates, with significance levels of P <0.05 for selection and P <0.01 for elimination.

Results

Both piperacillin PK and tazobactam PK were well described by a two-compartment model with first-order elimination. Creatinine clearance and body weight, as covariates on clearance (CL) and volume of central compartment (V1), were selected among the covariates possibly affecting PK parameters of both drugs. CL was defined as CL = 2.9 + 4.03 × CL_cr /47 for piperacillin and CL = 1.76 + 4.81 × CL_cr /47 for tazobactam. V1 was defined as V1 = 19.5 × weight/60 for piperacillin and V1 = 22.6 × weight/60 for tazobactam.

Conclusion

The PK profiles of TZP at a steady-state in Korean patients with acute infections were well described by a two-compartment model with first-order elimination. Both piperacillin and tazobactam clearances were significantly influenced by creatinine clearance.

Insulin degludec/insulin aspart in Japanese patients with type 1 diabetes mellitus: Distinct prandial and basal glucose-lowering effects

AIMS/INTRODUCTION

Insulin degludec/insulin aspart (IDegAsp) is a soluble co-formulation of long-acting insulin degludec (IDeg) and rapid-acting insulin aspart (IAsp). The present study investigated the pharmacodynamic properties of IDegAsp in Japanese patients with type 1 diabetes mellitus.

MATERIALS AND METHODS

In this randomized, double-blind, two-period, cross-over trial, 21 Japanese patients with type 1 diabetes mellitus received single doses of 0.5 U/kg IDegAsp and biphasic insulin aspart 30 in a randomized sequence (13-21 days washout between treatments). The pharmacodynamic response was evaluated in a 26-h euglycemic glucose clamp (target 5.5 mmol/L). Single-dose IDegAsp glucose infusion rate (GIR) profiles were extrapolated to steady state using modeling.

RESULTS

The IDegAsp single-dose GIR profile showed a clear distinction between the effects of the bolus (IAsp) and basal (IDeg) components in IDegAsp. When simulated to steady state, the GIR profile of IDegAsp was shifted upwards compared with the single-dose profile, and showed a rapid onset of action and a distinct peak from the IAsp component followed by a separate and sustained basal action from the long-acting IDeg component. For biphasic insulin aspart 30, the initial shape of the GIR profile was similar to IDegAsp, but GIR continuously decreased from maximum and reached zero 18-20 h post-dosing. The characteristics of the GIR profile for IDegAsp were retained when simulated to steady state in a twice-daily dosing regimen.

DISCUSSION

In Japanese patients with type 1 diabetes mellitus, the pharmacodynamic profile of IDegAsp is characterized by distinct prandial and basal effects from the IAsp and IDeg components, consistent with what has been reported previously in Caucasian patients with type 1 diabetes mellitus.

Influence of sex and race on mycophenolic acid pharmacokinetics in stable African American and Caucasian renal transplant recipients

BACKGROUND AND OBJECTIVES

No evaluation of sex and race influences on mycophenolic acid (MPA) pharmacokinetics and adverse effects (AEs) during enteric-coated mycophenolate sodium (ECMPS) and tacrolimus immunosuppression are available. The primary objective of this study was to investigate the influence of sex and race on MPA and MPA glucuronide (MPAG) pharmacokinetics in stable renal transplant recipients receiving ECMPS and tacrolimus

METHODS

The pharmacokinetics of MPA and MPAG and their associated gastrointestinal AEs were investigated in 67 stable renal transplant recipients: 22 African American males (AAMs), 13 African American females (AAFs), 16 Caucasian males (CMs), and 16 Caucasian females (CFs) receiving ECMPS and tacrolimus. A validated gastrointestinal AE rating included diarrhea, dyspepsia, vomiting, and acid-suppressive therapy was completed. Apparent clearance, clearance normalized to body mass index (BMI), area under the concentration-time curve from time zero to 12 h (AUC12) and dose-normalized AUC12 (AUC*) were determined using a statistical model that incorporated gastrointestinal AE and clinical covariates.

RESULTS

Males had more rapid apparent MPA clearance (CMs 13.8 ± 6.27 L/h vs. AAMs 10.2 ± 3.73 L/h) than females (CFs 8.70 ± 3.33 L/h and AAFs 9.71 ± 3.94 L/h; p = 0.014) with a race-sex interaction (p = 0.043). Sex differences were observed in MPA clearance/BMI (p = 0.033) and AUC* (p = 0.033). MPA AUC12 was greater than 60 mg·h/L in 57 % of renal transplant recipients (RTR) with 71 % of patients demonstrating gastrointestinal AEs and a higher score noted in females. In all patients, females exhibited 1.40-fold increased gastrointestinal AE scores compared with males (p = 0.024). Race (p = 0.044) and sex (p = 0.005) differences were evident with greater MPAG AUC12 in AAFs and CFs.

CONCLUSION

Sex and race differences were evident, with females having slower MPA clearance, higher MPAG AUC12, and more severe gastrointestinal AEs. These findings suggest sex and race should be considered during MPA immunosuppression.

Interethnic differences in pharmacokinetics of antibacterials

BACKGROUND

Optimal antibacterial dosing is imperative for maximising clinical outcome. Many factors can contribute to changes in the pharmacokinetics of antibacterials to the extent where dose adjustment may be needed. In acute illness, substantial changes in important pharmacokinetic parameters such as volume of distribution and clearance can occur for certain antibacterials. The possibility of interethnic pharmacokinetic differences can further complicate attempts to design an appropriate dosing regimen. Factors of ethnicity, such as genetics, body size and fat distribution, contribute to differences in absorption, distribution, metabolism and elimination of drugs. Despite extensive previous work on the altered pharmacokinetics of antibacterials in some patient groups such as the critically ill, knowledge of interethnic pharmacokinetic differences for antibacterials is limited.

OBJECTIVES

This systematic review aims to describe any pharmacokinetic differences in antibacterials between different ethnic groups, and discuss their probable mechanisms as well as any clinical implications.

METHODS

We performed a structured literature review to identify and describe available data of the interethnic differences in the pharmacokinetics of antibacterials.

RESULTS

We found 50 articles that met our inclusion criteria and only six of these compared antibacterial pharmacokinetics between different ethnicities within the same study. Overall, there was limited evidence available. We found that interethnic pharmacokinetic differences are negligible for carbapenems, most β-lactams, aminoglycosides, glycopeptides, most fluoroquinolones, linezolid and daptomycin, whereas significant difference is likely for ciprofloxacin, macrolides, clindamycin, tinidazole and some cephalosporins. In general, subjects of Asian ethnicity achieve drug exposures up to two to threefold greater than Caucasian counterparts for these antibacterials. This difference is caused by a comparatively lower volume of distribution and/or drug clearance.

CONCLUSION

Interethnic pharmacokinetic differences of antibacterials are likely; however, the clinical relevance of these differences is unknown and warrants further research.

Pharmacokinetic and pharmacodynamic properties of insulin degludec in Japanese patients with type 1 diabetes mellitus reflect similarities with Caucasian patients

Introduction

The present study aimed to evaluate the pharmacokinetic and pharmacodynamic properties of insulin degludec (IDeg) in Japanese patients with type 1 diabetes.

Materials and Methods

This was a randomized, single‐center, double‐blind, two‐period, crossover, multiple‐dose trial. Patients were randomized into two treatment sequences, and received IDeg or insulin detemir for 6 days and a washout period (7–21 days) before switching treatment. Blood samples for pharmacokinetic measurements were obtained before each dose and up to 120 h after the last dose of each treatment period. Pharmacodynamic measurements were obtained using a 26‐h euglycemic clamp procedure after the last dose of each treatment period.

Results

A total of 22 patients were randomized (14 men, 8 women; mean glycosylated hemoglobin at baseline of 7.5% [based on Japanese Diabetes Society value]). At steady state, total glucose‐lowering effect (area under the glucose infusion rate [GIR] curve during one dosing interval [τ, 0–24 h] at steady state [AUC_GIR,τ,SS]) was 1,446 mg/kg and total exposure (geometric mean) of IDeg (AUC_IDeg,τ,SS) was 81,270 pmol h/L. Both the glucose‐lowering effect and the exposure of IDeg were evenly distributed over the dosing interval, with AUC for the first 12‐h intervals being approximately 50% of the total (geometric mean; AUC_{GIR,0–12h,SS}/AUC_GIR,τ,SS = 48%; AUC_{IDeg,0–12h,SS}/AUC_IDeg,τ,SS = 53%).

Conclusions

IDeg has a flat, consistent and ultra‐long glucose‐lowering effect that is evenly distributed across a 24‐h interval and an ultra‐long duration of action in Japanese patients with type 1 diabetes. These data support once‐daily dosing of IDeg in all patients. Overall, the pharmacodynamic and pharmacokinetic end‐points and safety observations are consistent with those previously reported in Caucasian patients.

The clinical safety, biodistribution and internal radiation dosimetry of flutemetamol (¹⁸F) injection in healthy Japanese adult volunteers

Objectives

The Phase I safety, biodistribution and internal radiation dosimetry study in adult healthy Japanese males of flutemetamol (¹⁸F) injection, an in vivo β-amyloid imaging agent, is reported and compared with previously obtained Caucasian data.

Methods

Whole-body PET scans of 6 healthy volunteers (age 51.8–61.7 years) were acquired approximately 4 h post-injection (administered activity 102–160 MBq). Venous blood sampling determined ¹⁸F activity concentrations in whole blood and plasma and high-performance liquid chromatography (HPLC) established the percentages of parent [¹⁸F]flutemetamol and its metabolites. Voided urine activity was recorded. The decay-corrected and normalised ¹⁸F activity of 14 source organ regions as a function of time was entered into the OLINDA/EXM software to calculate the internal radiation dosimetry and effective dose of each subject following the MIRD schema. The pharmacokinetics, biodistribution and dosimetry profiles were compared to data obtained from a cohort of healthy Caucasian adult volunteers from a previous Phase I study of [¹⁸F]flutemetamol.

Results

Flutemetamol (¹⁸F) injection was well tolerated. The highest mean initial uptakes were measured in the liver (15.2 %), lungs (10.2 %) and brain (6.6 %). The highest mean radiation absorbed doses were received by the gallbladder wall (366 μGy/MBq), upper large intestine (138 μGy/MBq) and small intestine (121 μGy/MBq). The mean effective dose was 34.9 μSv/MBq. HPLC analysis demonstrated that at 5-min post-injection about 75 % of plasma ¹⁸F radioactivity was in the form of parent [¹⁸F]flutemetamol, reducing to 8 and 2 % at 25 and 90 min, respectively, giving rise to less lipophilic ¹⁸F-labelled metabolites. Comparisons with the Caucasian cohort showed no differences that could be regarded as clinically significant.

Conclusion

The clinical safety of [¹⁸F]flutemetamol demonstrated no differences of clinical significance in the pharmacokinetics, biodistribution and internal radiation dosimetry profiles between Caucasian and Japanese adults.

Liraglutide pharmacokinetics and dose-exposure response in Asian subjects with Type 2 diabetes from China, India and South Korea

AIMS

To investigate the population pharmacokinetics and exposure-response relationship of liraglutide, a human glucagon-like peptide-1 (GLP-1) analogue, in Asian subjects with Type 2 diabetes mellitus.

METHODS

Data were derived from a published 16-week, randomized, double-blind, double-dummy, active-controlled, parallel-group trial of liraglutide in China, India and South Korea. The analysis utilized 2061 pharmacokinetic (PK) samples from 605 subjects exposed to liraglutide 0.6, 1.2 or 1.8 mg once daily. Demographic factors (body weight, age, gender, country) of importance for liraglutide clearance were evaluated. An exploratory exposure-response analysis was conducted to investigate effects on glycated haemoglobin (HbA1c) and body weight.

RESULTS

Estimated liraglutide exposure (area under the curve; AUC) appeared to increase proportionally with increasing liraglutide dose (0.6-1.8 mg). The covariate analysis confirmed previous findings in a global clinical trial. Body weight was a predictor of liraglutide exposure; compared to a reference subject of 67 kg, exposure was 32% lower for maximum (115 kg) and 54% higher for minimum (37 kg) observed body weights. Gender, age and country had no relevant effect on exposure. Exposure-response analysis supported the use of 1.2mg as maintenance dose with the option of individual dose escalation to 1.8 mg to optimize treatment outcomes.

CONCLUSIONS

Exposure appeared to increase proportionally with increasing liraglutide dose in Asian subjects with Type 2 diabetes mellitus. The only PK relevant predictor of exposure was body weight. The exposure-response relationships for HbA1c and body weight in Asian subjects were similar to observations in global populations.

Insulin degludec/insulin aspart versus biphasic insulin aspart 30 in Asian patients with type 2 diabetes inadequately controlled on basal or pre-/self-mixed insulin: a 26-week, randomised, treat-to-target trial

AIMS

Insulin degludec/insulin aspart (IDegAsp) is a soluble co-formulation of IDeg and IAsp. This pan-Asian, 26-week trial investigated efficacy and safety of IDegAsp vs biphasic insulin aspart 30 (BIAsp 30) in Asian adults with type 2 diabetes (T2DM), inadequately controlled on once- or twice-daily (BID) basal, premixed or self-mixed insulin.

METHODS

Participants (mean age 59.8 years, HbA1c 8.4%, FPG 7.9 mmol/L, BMI 25.4 kg/m(2)) were randomised 2:1 to BID IDegAsp (n=282) or BIAsp 30 (n=142) and continued existing metformin treatment. Insulins were administered with breakfast and main evening meal, titrated to a pre-breakfast and pre-main evening meal self-measured plasma glucose target of 4-5 mmol/L.

RESULTS

IDegAsp achieved the primary endpoint of non-inferiority to BIAsp 30 for mean change in HbA₁c (estimated treatment difference [ETD] IDegAsp-BIAsp 30: 0.05% points [95% CI -0.10; 0.20]). IDegAsp was superior in lowering fasting plasma glucose (FPG) (ETD -1.06 mmol/L, 95% CI -1.43; -0.70, p<0.001), and resulted in a lower final mean daily insulin dose (0.79 U/kg vs 0.99 U/kg, estimated rate ratio [RR] 0.79, 95% CI 0.73; 0.85, p<0.0001). Rates of overall confirmed and severe hypoglycaemia were similar between treatments, while rate of nocturnal confirmed hypoglycaemia was numerically (p=ns) lower with IDegAsp. During the maintenance period there was a trend (p=ns) towards lower hypoglycaemia rates for IDegAsp.

CONCLUSION

In Asian adults with T2DM, IDegAsp BID effectively improves long-term glycaemic control, and compared to BIAsp 30, provides superior reductions in FPG with a lower dose, and numerically less nocturnal hypoglycaemia.

Pharmacokinetics, safety and tolerability of rotigotine transdermal patch in healthy Japanese and Caucasian subjects

Background and Objectives

Rotigotine is a dopamine receptor agonist with activity across the D₁ through to D₅ receptors as well as select serotonergic and adrenergic sites; continuous transdermal delivery of rotigotine with replacement of the patch once daily maintains stable plasma concentrations over 24 h. Rotigotine is indicated for the treatment of early and advanced-stage Parkinson’s disease and moderate-to-severe idiopathic restless legs syndrome. The pharmacokinetics and pharmacodynamics of a drug may vary between subjects of different ethnic origin. This study evaluated the pharmacokinetics, safety, and tolerability of single-dose treatment with rotigotine transdermal patch in Japanese and Caucasian subjects.

Methods

In this open-label, parallel-group study, healthy male and female subjects of Japanese or Caucasian ethnic origin were matched by sex, body mass index, and age. A single transdermal patch delivering 2 mg/24 h rotigotine (patch content 4.5 mg) was applied to the ventral/lateral abdomen for 24 h. The main outcome measures were the plasma concentrations of unconjugated and total rotigotine and its desalkyl metabolites and derived pharmacokinetic parameters (area under the concentration–time curve from time zero to last quantifiable concentration [AUC_last], maximum plasma concentration [C_max], and body weight- and dose-normalized values).

Results

The pharmacokinetic analysis included 48 subjects (24 Japanese, 24 Caucasian). The mean apparent dose of rotigotine was 2.0 ± 0.5 mg for Japanese subjects and 2.08 ± 0.58 mg for Caucasians. Plasma concentration–time profiles of unconjugated rotigotine and of the main metabolites were similar for both ethnic groups. Parameters of model-independent pharmacokinetics, C_max, time to C_max (t_max), and AUC_last, for unconjugated rotigotine showed no statistically significant differences between Japanese and Caucasian subjects. Values of concentration-dependent pharmacokinetic parameters were higher in female subjects; this difference was minimized after correction for body weight. A statistically significant difference between ethnic groups was observed for total rotigotine concentrations (total rotigotine = unconjugated rotigotine + conjugated rotigotine), with slightly lower values in Caucasians after correction for body weight and apparent dose. No relevant differences were observed between males and females. Inter-individual variability was high. The terminal half-life for unconjugated rotigotine was 5.3 h in Japanese subjects and 5.7 h in Caucasians; corresponding values for total rotigotine were 8.6 h and 9.6 h. Less than 0.1 % of the apparent dose was renally excreted as the parent compound. Renal elimination of total rotigotine covers 11.7 % of absorbed dose in Japanese subjects and 10.8 % of the absorbed dose in Caucasians, whereas the renal elimination via total despropyl rotigotine was 8.2 and 7.1 %, respectively. The corresponding values for total desthienylethyl rotigotine were 3.5 % in Japanese subjects and 4.2 % Caucasians. Most adverse events were mild in intensity and typical for dopamine agonists or for transdermal therapeutics.

Conclusion

Administration of a single patch delivering 2 mg/24 h rotigotine resulted in comparable pharmacokinetic profiles in Japanese and Caucasian subjects. The rotigotine transdermal patch was generally well-tolerated. Our findings suggest similar dose requirements for Japanese and Caucasian populations.

Ethnic comparison of pharmacokinetics of (18)F-florbetaben, a PET tracer for beta-amyloid imaging, in healthy Caucasian and Japanese subjects

PURPOSE

(18)F-Florbetaben is a positron emission tomography (PET) tracer indicated for imaging cerebral beta-amyloid deposition in adult patients with cognitive impairment who are being evaluated for Alzheimer's disease and other causes of cognitive decline. The present study examined ethnic comparability of the plasma pharmacokinetics, which is the input to the brain, between Caucasian and Japanese subjects.

METHODS

Two identical phase I trials were performed in 18 German and 18 Japanese healthy volunteers to evaluate the plasma pharmacokinetics of a single dose of 300 MBq (18)F-florbetaben, either of low (≤5 μg, LD) or high (50-55 μg, HD) mass dose. Pharmacokinetic parameters were evaluated based on the total (18)F radioactivity measurements in plasma followed by metabolite analysis using radio-HPLC.

RESULTS

The pharmacokinetics of (18)F-florbetaben was characterized by a rapid elimination from plasma. The dose-normalized areas under the curve of (18)F-florbetaben in plasma as an indicator of the input to the brain were comparable between Germans (LD: 0.38 min/l, HD: 0.55 min/l) and Japanese (LD: 0.35 min/l, HD: 0.45 min/l) suggesting ethnic similarity, and the mass dose effect was minimal. A polar metabolite fraction was the main radiolabelled degradation product in plasma and was also similar between the doses and the ethnic groups.

CONCLUSION

Absence of a difference in the pharmacokinetics of (18)F-florbetaben in Germans and Japanese has warranted further global development of the PET imaging agent.

Bortezomib-associated peripheral neuropathy requiring medical treatment is decreased by administering the medication by subcutaneous injection in Korean multiple myeloma patients

PURPOSE

Bortezomib-induced peripheral neuropathy (BIPN) is a significant neurotoxicity, requiring dose reduction or the delay of treatment. In a multicentre trial including 97 % Caucasians and 3 % Asians, BIPN was shown to occur less frequently in cases in which bortezomib was administered subcutaneously. Considering the different pharmacokinetics between Caucasians and Asians, we analysed BIPN according to the administration route, specifically in Korean myeloma patients.

METHODS

We surveyed the prescribed anticonvulsants for the treatment of BIPN and analysed the data after stratifying the results by the cumulative dose of bortezomib. Exclusion criteria were as follows: treated with <2 doses of bortezomib, change in the administration route during the treatment, or receiving anticonvulsants for other reasons prior to bortezomib administration.

RESULTS

A total of 101 patients were enrolled; 60 were treated with bortezomib and dexamethasone, and 37 were treated with bortezomib, melphalan, and prednisolone. The median number of treatment courses was four for each regimens. The median exposure to bortezomib for all patients was 19 mg/m(2). Progression-free survival (PFS) and overall survival rates were not statistically different between the groups. There was no difference in the proportion of patients requiring medical treatment (p = 0.388). After stratifying the results, BIPN developed less frequently when bortezomib was administered subcutaneously rather than intravenously in patients receiving more than 23.4 mg/m(2) of bortezomib (p < 0.05).

CONCLUSION

Since the responses were potent regardless of administration route, the subcutaneous injection of bortezomib should be considered in Asian myeloma patients who are expected to achieve a longer PFS with bortezomib.

Single-dose pharmacokinetics of the HCV polymerase inhibitor mericitabine in healthy Caucasian and Japanese subjects

To investigate the pharmacokinetics of mericitabine in healthy Caucasian and Japanese subjects, healthy Caucasian (n = 32) and Japanese (n = 32) subjects were randomized to receive single 500, 1,000, or 2,000 mg doses of mericitabine or a placebo, after which plasma and urine samples were collected for 72 h. Mericitabine (prodrug), RO4995855 (parent), and RO5012433 (uridine metabolite) concentrations were quantified by tandem mass spectrometry. Pharmacokinetics were estimated by non-compartmental methods, and pharmacokinetic parameters of RO4995855 were normalized by body weight. Exposure to RO4995855 was similar in both populations after administration of mericitabine 500, 1,000, and 2,000 mg. Mean AUCinf of RO4995855 increased in a dose-proportional manner from 28.8 to 52.3, and 113.0 µg·h/mL in Caucasian subjects, and from 32.5 to 57.1 and 119 µg·h/mL in Japanese subjects. A linear relationship was observed between the weight-adjusted dose of mericitabine and Cmax (r(2) = 0.83 and 0.80) and AUC (r(2) = 0.94 and 0.74) for RO4995855 in Caucasian and Japanese subjects, respectively. Mean half-life and renal clearance of RO4995855 were similar and independent of dose in both populations. The results support the use of the same dosing regimens in Caucasian and Asian subjects.

Do we need to consider ethno-cultural variation in the use of atypical antipsychotics for Asian patients with major depressive disorder?

Asian and western countries differ in the prevalence, symptom manifestation, diagnostic procedures, patient recognition and treatments of major depressive disorder (MDD), according to a number of studies. Ethnic differences in pharmacological profiles are also important in the prescription of certain antipsychotic medications because they may impact treatment outcomes and adverse events. Differential pharmacokinetic and pharmacodynamic properties of antipsychotics may be practically useful in the control of specific depressive symptoms. Furthermore, patient compliance with prescribed medications has been found to be different across races and ethnicities. Therefore, this article explores practical clinical issues for the use of atypical antipsychotics in patients with MDD, focusing on ethno-cultural differences.

Ethnic variability in the plasma exposures of OATP1B1 substrates such as HMG-CoA reductase inhibitors: a kinetic consideration of its mechanism

Because the plasma exposure levels of rosuvastatin in Asians are generally twice those in Caucasians, the starting dose for Asians in the United States is set to half of that for non-Asians. However, the precise role of ethnicity in the clearance of rosuvastatin has not yet been clarified. This review focuses on ethnic variability in the clinical pharmacokinetics of 3-hydroxy-3-methylglutaryl co-enzyme A (HMG-CoA) reductase inhibitors (statins) and angiotensin II receptor antagonists. The mechanisms of such variability are discussed quantitatively, with building a hypothetical model for pravastatin, and validated against other statins. Our analyses suggest that the ethnic variability in the plasma exposure of statins cannot be explained only by the difference in the allele frequencies of organic anion-transporting polypeptide (OATP)1B1 and breast cancer resistance protein (BCRP), and the intrinsic ethnic variability in the activity of OATP1B1 (the ratio of Japanese/Caucasians is 0.584) must be considered. Further work and validation with additional data will clarify the applicability of this model to other OATP1B1 substrates.

Prucalopride in the treatment of chronic constipation in patients from the Asia-Pacific region: a randomized, double-blind, placebo-controlled study

BACKGROUND

The study evaluated efficacy and safety of the 2 mg dose of prucalopride compared to placebo in patients with chronic constipation (CC) from the Asia-Pacific region.

METHODS

Randomized, placebo-controlled, parallel-group, phase III study with 2-week run-in, 12-week treatment phase, and 1-week follow-up. Adult patients with CC (≤2 spontaneous bowel movements per week) received 2 mg prucalopride or placebo, once-daily, for 12 weeks. Primary efficacy measure was percentage of patients with average of ≥3 spontaneous complete bowel movements (SCBMs) per week (Responders) during the 12-week treatment. A key secondary endpoint was Responders during first 4 weeks of treatment. Other efficacy assessments were based on patient diaries, their assessments of symptoms and quality of life, and investigator's assessment on efficacy of treatment. Safety assessments included adverse events, laboratory values, and cardiovascular events.

KEY RESULTS

Efficacy and safety were evaluated for 501 patients who received study drug. On the primary endpoint, prucalopride was significantly more effective than placebo with 83 (33.3%) vs 26 (10.3%) patients having a weekly average of ≥3 SCBMs during the 12-week treatment (P < 0.001). Respective percentages were 34.5%vs 11.1% over first 4 weeks (P < 0.001). On other secondary endpoints, clinical improvement was generally larger and statistically superior (P < 0.001) in the prucalopride group. Most frequently reported adverse events were diarrhea, nausea, abdominal pain, and headache.

CONCLUSION & INFERENCES

Prucalopride 2 mg given once-daily significantly improved bowel function, associated symptoms, and satisfaction in CC over a 12-week treatment period, and was safe and well tolerated by patients in the Asia-Pacific region.

Propofol pharmacokinetics in young healthy Indian subjects

OBJECTIVES

To analyze population pharmacokinetics of Propofol in Indian patients after single bolus dose of Propofol using WINNONLIN program.

MATERIALS AND METHODS

Population pharmacokinetics of Propofol was investigated in Indian subjects in 26 elective surgical patients (14 males and 12 females) following single bolus dose of 2 mg/kg propofol. A total of 364 samples were estimated by High Performance Liquid Chromatography and pharmacokinetic parameters were derived using WINNONLIN (5.2). The effect of demographic characters of the study population on pharmacokinetic parameters was investigated.

RESULTS

Three-compartment model was used to describe the pharmacokinetic data of Propofol in Indian subjects. Initial volume of distribution (V1) clearance (Cl) and steady state volume of distribution (Vd(ss)) was 13.5 ± 3.3 l, 1.08 ± 0.42 l/min, and 77.69 ± 48.0 l, respectively. Body weight best described the volume of central compartment (V1) as well as elimination clearance (P<0.01).

CONCLUSION

Pharmacokinetics of Propofol in young healthy Indian subjects show lower volume of distribution and clearance as compared with most of the western data. Body weight best describes the V1, Vd(ss), and Clearance in this group.

Safety, pharmacokinetics and pharmacodynamics of four-hour intravenous infusions of eritoran in healthy Japanese and Caucasian men

Eritoran, a synthetic analogue of lipid A, has been shown to bind to TLR4/MD-2 complex and thereby block the interaction of endotoxins with TLR4. We report here the results of a study conducted to assess the single-dose safety and tolerability, as well as the pharmacokinetics and pharmacodynamics, of eritoran infusion in Japanese and Caucasian healthy adult men. Sixty-four men (aged 20-45 years; body mass index 18-30 kg/m(2)) were randomized into four groups: 4-mg total dose (six Japanese and six Caucasian men); 12-mg total dose (12 Japanese and 12 Caucasian men); 28-mg total dose (six Japanese and six Caucasian men); and placebo (eight Japanese and eight Caucasian men). Eritoran in single doses up to 28 mg over 4 h was well tolerated, with no apparent ethnic differences noted. Plasma concentrations were slightly higher in Japanese versus Caucasian men; these differences were not significant after adjustment for differences in body mass (clearance: approximately 1.2 ml/h/kg; volume of distribution at steady state: approximately 0.07 l/kg). The ex vivo endotoxin inhibitory activity of eritoran was similar in Japanese and Caucasian men. The data do not indicate any need for clinical dose adjustment for possible ethnic-based differences in drug distribution or metabolism.

Treatment of culturally diverse children and adolescents with depression

This article is written for the practitioners treating depression in ethnic minority youth. It will review the context in which services are delivered to these youth: Researchers have recognized persistent ethnic differences in terms of utilization of services and unmet need. Furthermore, when ethnic minority youth do receive pediatric mental health care, the services that they receive may differ from those given to White patients. The reasons for these discrepancies have been examined in numerous studies, and have included contextual variables (economics, availability, and accessibility of services), patient variables (differences in prevalence or manifestation of the disorder, cultural beliefs and attitudes, preferential use of alternative or informal services, health literacy, and adherence), and provider variables (referral bias and patient-provider communication). Information about the differences between White and minority youth in the pharmacodynamics and pharmacokinetics of the antidepressant response is still limited. There are significant challenges for developing evidence-based guidelines that inform practice with these youth, hinging on both the underrepresentation of ethnic minority groups in clinical trials, and the great variability in biological and cultural characteristics of individuals in ethnic minority categories. Awareness on the part of the practitioner of the cultural variables that influence help-seeking and ongoing utilization of mental health services may aid in the engagement, effective treatment, and retention of ethnic minority children and adolescents with depression. However, given the great heterogeneity that exists within any cultural grouping, clinicians will need to integrate information about cultural patterns with that obtained from the individual patient and family to inform optimal practices for each patient. This article is written to enhance awareness on the part of the practitioner as to the variables that influence psychiatric care for depression in culturally diverse youth. The mental health needs of minority youth are not well served: They are treated less frequently, and when they are treated, the services they receive are less frequently adequate. The reasons that have been proposed for the disparities in their care, particularly with regard to diagnosis and treatment for depression, will be reviewed. They include contextual factors (such as economics, insurance, and other variables affecting the availability of services) patient and family factors (such as prevalence, symptom presentation, and values and beliefs that influence whether patients are referred to and avail themselves of services), and provider factors (such as referral bias and patient-provider communication, which affect whether patients engage and stay in treatment). The implications for the practitioner treating ethnic minority youth with depression will be discussed. Culture, as used in this article, refers to the common values, beliefs, and social behaviors of individuals with a shared heritage. Some aspects of culture that are likely to influence service utilization include health beliefs, particularly regarding models of mental illness, and level of stigma toward mental health treatment, which are frequently shared by individuals in a cultural group. However, some caveats for the explanatory potential of "culture" should be kept in mind. Conventions for naming groups vary between investigators and over time (e.g., the restriction of the category "White" into "White NonHispanic," is quite recent). Although heterogeneity is assumed within a named cultural or racial group, the terms Hispanic, Asian, and African-American incorporate subgroups can be very different in linguistic, historical, and geographical ancestry (e.g., Stewart 2008 ), and each group incorporates individuals who may not share any components of their historical heritage. Even among those with historical ties, values, beliefs, and social behaviors can vary according to the extent to which they identify with the mainstream culture. Social class frequently creates a "culture" of its own, with individuals in the same social class across traditional cultural groupings sharing disparities in care, and many beliefs and values. Individuals are likely to belong to numerous "cultures," and may not share specific typical behaviors or beliefs with any of them.

Adjunctive benzodiazepine treatment of hospitalized schizophrenia patients in Asia from 2001 to 2008

Benzodiazepines are commonly prescribed to patients with schizophrenia in many countries, but as little is known about such treatment in Asia, we evaluated their adjunctive use for 6761 in-patients diagnosed with schizophrenia in nine Asian countries using a cross-sectional study design in 2001, 2004 and 2008. Multivariate logistic regression and multivariate linear regression analyses were performed to assess predictors of benzodiazepine use and dose, respectively. Overall, 54% of the patients received adjunctive benzodiazepines at an average daily dose equivalent to 30.3 mg diazepam, with minor changes over the years sampled. Benzodiazepine use was highest in Taiwan and Japan, lowest in Thailand and China, and was associated with fewer years ill, presence of delusions (OR 1.24), hallucinations (OR 1.22), disorganized speech (OR 1.17), social or occupational dysfunction (OR 1.16), and use of mood stabilizers (OR 3.15), antiparkinsonian (OR 1.79) or antidepressant drugs (OR 1.33), and lower doses of antipsychotics (all p=0.016 to <0.001). Benzodiazepine doses were highest in Taiwan and China, lowest in Korea and Singapore; higher doses were associated with being young, male, physically aggressive, receiving mood stabilizers, and having electroconvulsive treatment (all p=0.019 to <0.001). Benzodiazepine use was associated with neurological and systemic adverse effects. In conclusion, benzodiazepine use was common in Asian patients with schizophrenia. Predictors of benzodiazepine use and dose differed in this population. Critical clinical guidelines should be developed specifically for Asian countries to address sound practices in regard to use of benzodiazepines for psychotic disorders.

Impact of race/ethnicity on the efficacy and safety of commonly used insulin regimens: a post hoc analysis of clinical trials in type 2 diabetes mellitus

OBJECTIVE

To explore the impact of race/ethnicity on the efficacy and safety of commonly used insulin regimens in patients with type 2 diabetes mellitus.

METHODS

In this post hoc analysis, pooled data from 11 multinational clinical trials involving 1455 patients with type 2 diabetes were used to compare specific insulin treatments in Latino/Hispanic, Asian, African-descent, and Caucasian patients. Insulin treatments included once daily insulin glargine or neutral protamine Hagedorn (BASAL), insulin lispro mix 75/25 twice daily (LMBID), or insulin lispro mix 50/50 three times daily (LMTID).

RESULTS

Race/ethnicity was associated with significant outcome differences for each of the insulin regimens. BASAL therapy was associated with greater improvement in several measures of glycemic control among Latino/Hispanic patients compared with Caucasian patients (lower end point hemoglobin A1c, greater reduction in hemoglobin A1c from baseline, and a larger proportion of patients achieving hemoglobin A1c level <7%). In contrast, LMBID therapy was associated with higher end point hemoglobin A1c and a smaller decrease in hemoglobin A1c from baseline in Latino/Hispanic and Asian patients than in Caucasian patients. Furthermore, fewer Asian patients attained a hemoglobin A1c level <7% than did Caucasians patients. For LMTID therapy, hemoglobin A1c outcomes were comparable across patient groups. Fasting blood glucose and glycemic excursions varied among racial/ethnic groups for the 3 insulin regimens. Weight change was comparable among racial/ethnic groups in each insulin regimen. During treatment with LMTID, Asian patients experienced higher incidence and rate of severe hypoglycemia than Caucasian patients.

CONCLUSIONS

Latino/Hispanic, Asian, and African-descent patients with type 2 diabetes show different metabolic responses to insulin therapy, dependent in part on insulin type and regimen intensity.

Effects of coping skills training and sertraline in patients with non-cardiac chest pain: a randomized controlled study

Non-cardiac chest pain (NCCP) is a common and distressing condition. Prior studies suggest that psychotropic medication or pain coping skills training (CST) may benefit NCCP patients. To our knowledge, no clinical trials have examined the separate and combined effects of CST and psychotropic medication in the management of NCCP. This randomized clinical trial examined the separate and combined effects of CST and antidepressant medication (sertraline) in participants with non-cardiac chest pain. A sample of individuals diagnosed with NCCP was randomly assigned to one of four treatments: (1) CST plus sertraline (CST+sertraline), (2) CST plus placebo (CST+placebo), (3) sertraline alone, or (4) placebo alone. Assessments of pain intensity, pain unpleasantness, anxiety, pain catastrophizing, depression, and physical disability were collected prior to treatment, and at 10- and 34-weeks following randomization. Data analyses revealed that CST and sertraline either alone or in combination significantly reduced pain intensity and pain unpleasantness. The combination of CST plus sertraline may have the greatest promise in that, when compared to placebo alone, it not only significantly reduced pain but also pain catastrophizing and anxiety. Overall, these findings support the importance of further research on the effects of CST and sertraline for non-cardiac chest pain.

Pharmacokinetic variability of long-acting stimulants in the treatment of children and adults with attention-deficit hyperactivity disorder

Methylphenidate- and amfetamine-based stimulants are first-line pharmacotherapies for attention-deficit hyperactivity disorder, a common neurobehavioural disorder in children and adults. A number of long-acting stimulant formulations have been developed with the aim of providing once-daily dosing, employing various means to extend duration of action, including a transdermal delivery system, an osmotic-release oral system, capsules with a mixture of immediate- and delayed-release beads, and prodrug technology. Coefficients of variance of pharmacokinetic measures can estimate the levels of pharmacokinetic variability based on the measurable variance between different individuals receiving the same dose of stimulant (interindividual variability) and within the same individual over multiple administrations (intraindividual variability). Differences in formulation clearly impact pharmacokinetic profiles. Many medications exhibit wide interindividual variability in clinical response. Stimulants with low levels of inter- and intraindividual variability may be better suited to provide consistent levels of medication to patients. The pharmacokinetic profile of stimulants using pH-dependent bead technology can vary depending on food consumption or concomitant administration of medications that alter gastric pH. While delivery of methylphenidate with the transdermal delivery system would be unaffected by gastrointestinal factors, intersubject variability is nonetheless substantial. Unlike the beaded formulations and, to some extent (when considering total exposure) the osmotic-release formulation, systemic exposure to amfetamine with the prodrug stimulant lisdexamfetamine dimesylate appears largely unaffected by such factors, likely owing to its dependence on systemic enzymatic cleavage of the precursor molecule, which occurs primarily in the blood involving red blood cells. The high capacity but as yet unidentified enzymatic system for conversion of lisdexamfetamine dimesylate may contribute to its consistent pharmacokinetic profile. The reasons underlying observed differential responses to stimulants are likely to be multifactorial, including pharmacodynamic factors. While the use of stimulants with low inter- and intrapatient pharmacokinetic variability does not obviate the need to titrate stimulant doses, stimulants with low intraindividual variation in pharmacokinetic parameters may reduce the likelihood of patients falling into subtherapeutic drug concentrations or reaching drug concentrations at which the risk of adverse events increases. As such, clinicians are urged both to adjust stimulant doses based on therapeutic response and the risk for adverse events and to monitor patients for potential causes of pharmacokinetic variability.

Incidence and risk factors of severe adverse events with nevirapine-based antiretroviral therapy in HIV-infected women. MTCT-Plus program, Abidjan, Côte d'Ivoire

Background

In resource-limited settings where nevirapine-containing regimen is the preferred regimen in women, data on severe adverse events (SAEs) according to CD4 cell count are limited. We estimated the incidence of SAEs according to CD4 cell count and identify their risk factors in nevirapine-treated women.

Methods

All HIV-infected women who initiated nevirapine-containing regimen in the MTCT-Plus operational program in Abidjan, Côte d'Ivoire, were eligible for this study. Laboratory and clinical (rash) SAEs were classified as grade 3 and 4. Cox models were used to identify factors associated with the occurrence of SAEs.

Results

From August 2003 to October 2006, 290 women initiated a nevirapine-containing regimen at a median CD4 cell count of 186 cells/mm³ (IQR 124-266). During a median follow-up on treatment of 25 months, the incidence of all SAEs was 19.5/100 patient-years. The 24-month probability of occurrence of hepatotoxicity or rash was not different between women with a CD4 cell count >250 cells/mm³ and women with a CD4 cell count ≤250 cells/mm³ (8.3% vs. 9.9%, Log-rank test: p = 0.75). In a multivariate proportional hazard model, neither CD4 cell count >250 cells/mm³ at treatment initiation nor initiation NVP-based regimen initiated during pregnancy were associated with the occurrence of SAEs.

Conclusion

CD4 cell count >250 cells/mm³ was not associated with a higher risk of severe hepatotoxicity and/or rash, as well as initiation of ART during pregnancy. Pharmacovogilance data as well as meta-analysis on women receiving NVP in these settings are needed for better information about NVP toxicity.

The effect of selective serotonin reuptake inhibitors in healthy subjects. A systematic review

BACKGROUND

Selective serotonin reuptake inhibitors (SSRIs) show antidepressant properties in many patients with a diagnosis of depression. An understanding of the underlying mechanisms of the effect of SSRIs in healthy patients may lead to an understanding of the yet unclear pathophysiology of depression. Recent reviews of studies investigating the effect of SSRIs in healthy persons conclude that the results are inconsistent and that--in relation to a wide range of outcomes--the effect of SSRIs is limited; however, reasons for the inconsistencies are poorly studied.

AIMS AND METHODS

To investigate whether methodological artefacts can explain the diverging findings, we conducted a systematic review of all randomized multiple-dose, placebo-controlled trials on the effect of treatment by SSRI for at least a week in healthy persons published before January 2009.

RESULTS

We identified 33 trials, investigating six SSRIs and 163 outcome tests. The effect of SSRI showed divergence presumably related to methodological issues. Specifically, it is likely that the majority of studies included a mix of healthy persons with and without a family history of affective disorders. Few presented information on factors that may influence outcomes such as age, gender, family history of psychiatric disorder, drug levels and ethnicity. No study fulfilled principles of conducting and reporting randomized controlled trials, according to the CONSORT Statement guidelines.

CONCLUSIONS

It is unclear whether the effect of SSRIs in healthy persons may lead to an understanding of the pathophysiology of depression, since the present evidence is divergent and may be severely influenced by a number of methodological drawbacks.

Exploring differences in drug doses between Japan and Western countries

Japan is unique among Asian countries in that it requires inclusion of substantial domestic clinical trial data in new drug application data packages. Some question the need for this and call for globalization of approved doses. The current study examines international differences in maximum daily dose of drugs approved in Japan between 2001 and 2007, and for all cardiovascular system (CVS) and central nervous system (CNS) drugs marketed in Japan. For 32% of the drugs approved in Japan between 2001 and 2007, the maximum recommended dose in the United States was > or =2 times higher than the maximum dose approved in Japan. Dose differences were rare for antitumor and antiviral drugs and also for priority-review and orphan drugs. Of all the price-listed CVS drugs currently available in Japan, 65% had maximum doses that were > or =2 times higher in the Netherlands than in Japan; similarly, 57% of the drugs had maximum doses that were > or =2 times higher in the United States than in Japan. For CNS drugs, these figures were 32% (the Netherlands) and 29% (United States). These results underscore the necessity to carry out quantitative analyses to determine the causes of these differences.

Liver transplantation in the ethnic minority population: challenges and prospects

In the USA, end-stage liver disease (ESLD) is a major cause of morbidity and mortality among ethnic minorities. Ethnic populations vary with respect to chronic liver disease prevalence, access to transplantation, and therapeutic outcomes post liver transplantation. These ethnic differences present unique challenges to healthcare professionals involved in the care of patients with chronic liver disease prior and post transplantation. This review will discuss the variations and challenges of liver transplantation in the ethnic minority population.

Global variation in CYP2C8-CYP2C9 functional haplotypes

We have studied the global frequency distributions of 10 single nucleotide polymorphisms (SNPs) across 132 kb of CYP2C8 and CYP2C9 in ∼2500 individuals representing 45 populations. Five of the SNPs were in noncoding sequences; the other five involved the more common missense variants (four in CYP2C8, one in CYP2C9) that change amino acids in the gene products. One haplotype containing two CYP2C8 coding variants and one CYP2C9 coding variant reaches an average frequency of 10% in Europe; a set of haplotypes with a different CYP2C8 coding variant reaches 17% in Africa. In both cases these haplotypes are found in other regions of the world at <1%. This considerable geographic variation in haplotype frequencies impacts the interpretation of CYP2C8/CYP2C9 association studies, and has pharmacogenomic implications for drug interactions.

Pharmacokinetics of hydroxychloroquine and its clinical implications in chemoprophylaxis against malaria caused by Plasmodium vivax

Hydroxychloroquine (HCQ) is an antimalarial drug used as chemoprophylaxis against malaria caused by Plasmodium vivax in the Republic of Korea Army (ROKA). In this study, we evaluated the pharmacokinetics (PK) of HCQ and its metabolites and the relationship between the PK of HCQ and the effect of treatment of HCQ on vivax malaria in South Koreans. Three PK studies of HCQ were conducted with 91 healthy subjects and patients with vivax malaria. Plasma concentrations were analyzed by noncompartmental and mixed-effect modeling approaches. A two-compartment model with first-order absorption best described the data. The clearance and the central and peripheral volumes of distribution were 15.5 liters/h, 733 liters, and 1,630 liters, respectively. We measured the plasma concentrations of HCQ in patients with prophylactic failure of HCQ and compared them with the prediction intervals of the simulated concentrations for HCQ from the final PK model built in this study. In 71% of the patients with prophylactic failure, the plasma concentrations of HCQ were below the lower bounds of the 95% prediction interval, while only 8% of them showed higher levels than the upper bounds of the 95% prediction interval. We report that a significant cause of prophylactic failure among the individuals in ROKA was ascribed to plasma concentrations of HCQ lower than those predicted by the PK model. However, prophylactic failure despite sufficient plasma concentrations of HCQ was confirmed in several individuals, warranting continued surveillance to monitor changes in the HCQ susceptibility of Plasmodium vivax in the Republic of Korea.