Sirimas Kanjanawart

Comparative bioavailability of two moxifloxacin tablet products after single dose administration under fasting conditions in a balanced, randomized and cross-over study in healthy volunteers.

Moxifloxacin, a 4th generation of fluoroquinolones, is a broad spectrum antibacterial agent against respiratory tract pathogens, including Gram-positive and Gram-negative bacteria, anaerobic bacteria and atypical respiratory tract pathogens. In order to evaluate the efficacy and safety of generic moxifloxacin products, the bioequivalence of these generic products with an approved reference formulation should be demonstrated. Thus, the aim of this study was to compare the rate and extent of absorption of a new generic film coated moxifloxacin tablet product (Rapiflox®, Atlantic Laboratories Corporation Ltd., Bangkok, Thailand) with that of a reference product (Avelox®, Bayer Health Care AG, Leverkusen, Germany) when given as a single dose. A crossover study was performed in 20 healthy Thai volunteers. The subjects received either a 400 mg tablet of the reference or test product after overnight fasting. Blood samples were collected at pre-dose (0 hour) and at 0.25, 0.5, 1, 1.5, 2, 3, 4, 6, 8, 12, 24 and 34 hours post-dose. Moxifloxacin plasma level was measured by a validated HPLC method with fluorescence detector. Pharmacokinetic parameters were calculated using a non-compartmental model. The geometric mean of maximum concentration (Cmax) of the test product was 4,069.64 ng/ml, with median time to achieve maximum concentration (tmax) at 2 hours (range 0.25 - 6.00 hours), while the geometric mean Cmax and median tmax of the reference product was 4,211.98 ng/ml and 2.00 hours (range 0.25 - 8.00 hours). Furthermore, the geometric means of AUC0-tlast and AUC0-∞ for the test product were 49,731.66 and 51,865.89 ng×h/ml while those of the reference product were 51,927.97 and 54,455.93 ng×h/ml. The geometric mean of the ratios of Test/Reference for the logtransformed Cmax, AUC0-tlast and AUC0-∞ of moxifloxacin and their 90% CIs were 96.62% (83.21 - 112.19%), 95.77% (87.07 - 105.34%) and 95.24 (86.52 - 104.85%), respectively. Therefore, it can be concluded that these two moxifloxacin tablet products were bioequivalent in healthy Thai volunteers under fasting condition.

Bioequivalence study of two meloxicam tablet formulations after single-dose administration in healthy Thai male volunteers.

OBJECTIVES To compare the bioavailability of two meloxicam tablet formulations (MEL-OD, Zydus Cadila Healthcare Limited, India, as a test formulation and Mobic, Boehringer Ingelheim International GmbH, Germany, as a reference formulation) in healthy Thai male volunteers under fasting condition. MATERIALS AND METHODS A randomized, 2-treatment, 2-period, 2-sequence, single dose, crossover with a washout period of 2 weeks, was conducted in 26 healthy Thai male volunteers. Blood samples were collected 0, 1, 2, 3, 3.5, 4, 4.5, 5, 5.5, 6, 7, 8, 10, 12, 24, 36, 48, 72 and 96 h post dose. Plasma concentrations of meloxicam were determined using a validated HPLC method. The pharmacokinetic parameters of meloxicam were determined using a non-compartmental model. RESULTS The mean Cmax was 1,027.32 +/- 251.91 and 1,151.89 +/- 282.58 ng/ml while the mean AUC0-t was 34,024.31 +/- 11,811.68 and 35,137.66 +/- 11,970.47 ng x h/ml for the test and reference formulation, respectively. In addition, the mean AUC0-infinity for test formulation was 37,241.44 +/- 14,888.85 ng x h/ml and for the reference formulation was 39,541.04 +/- 16,624.64 ng x h/ml. The median tmax for the test and reference formulation was 4.50 (range 2.00 - 12.00) and 4.50 (range 3.00 - 10.00), respectively. The geometric means (90% confidence intervals) of the ratio for the log-transformed pharmacokinetic parameters, Cmax, AUC0-t and AUC0-inf were 0.8919 (82.58 - 96.32%), 0.9697 (89.46 - 105.10%) and 0.9525 (87.68 - 103.47%), respectively. CONCLUSIONS It can be concluded that two meloxicam tablet formulations are bioequivalent both in term of rate and extent of absorption after single-dose administration under fasting condition.

HLA Pharmacogenetic Markers of Drug Hypersensitivity in a Thai Population

Severe cutaneous adverse drug reactions (SCARs) including Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), and drug reactions with eosinophilia and systemic symptoms (DRESS) are potentially life-threatening cutaneous reactions caused by several drugs. Recently, a number of genes encoding for human antigen presenting proteins, HLA alleles, have been discovered as valid pharmacogenetic markers for prediction of these life-threatening reactions. This study was aimed to determine the distribution of HLA alleles including the HLA class I and class II genes in 183 unrelated individuals of a Thai population using high resolution HLA genotyping in order to obtain 2-field data (4-digit resolution) and compare the frequencies of the HLA alleles that have been proposed as markers of SCARs with other ethnics. Results revealed a high prevalence of pharmacogenetic markers of drug-induced SCARs e.g., B*13:01 for dapsone; B*15:02 for carbamazepine and oxcarbazepine; B*58:01, A*33:03 and C*03:02 for allopurinol; C*08:01, C*14:02 and DRB1*12:02 for co-trimoxazole. Whereas, low prevalence of pharmacogenetic markers of SCARs induced by abacavir, B*57:01 and phenytoin, B*56:02/B*56:04 were noticed. The allele frequencies of B*13:01, B*15:02, and B*58:01 observed in a Thai population were significantly higher than those reported in Japanese and Caucasian populations. Similar to those observed in other Southeast Asian populations, low frequencies of A*31:01 and B*57:01 alleles were noted in the study population. Based on the frequencies of HLA pharmacogenetic markers, Thai and other Southeast Asian populations may at higher risk of drug-induced SCARs compared with Caucasian population.

Comparison between the HLA-B58 : 01 Allele and Single-Nucleotide Polymorphisms in Chromosome 6 for Prediction of Allopurinol-Induced Severe Cutaneous Adverse Reactions

Severe cutaneous adverse drug reactions (SCARs) are life-threatening reactions. The strong association between the HLA-B∗58 : 01 allele and allopurinol-induced SCARs is well recognized. Screening for HLA-B∗58 : 01 allele before prescribing allopurinol in some populations has been recommended. Several single-nucleotide polymorphisms (SNPs) in chromosome 6 have been found to be tightly linked with the HLA allele, and these SNPs have been proposed as surrogate markers of the HLA-B∗58 : 01 allele. This study aimed to evaluate the association between three SNPs in chromosome 6 and allopurinol-induced SCARs in a Thai population. The linkage disequilibrium between the HLA-B∗58 : 01 allele and these SNPs was also evaluated. Results showed that three SNPs including rs9263726, rs2734583, and rs3099844 were significantly associated with allopurinol-induced SCARs but with a lower degree of association when compared with the HLA-B∗58 : 01 allele. The sensitivity, specificity, PPV, and NPV of these SNPs were comparable to those of the HLA-B∗58 : 01 allele. Although detection of the SNP is simpler and less expensive compared with that of the HLA-B∗58 : 01 allele, these SNPs were not perfectly linked with the HLA-B∗58 : 01 allele. Screening using these SNPs as surrogate markers of the HLA-B∗58 : 01 allele to avoid SCARs prior to allopurinol administration needs caution because of their imperfect linkage with the HLA-B∗58 : 01 allele.