Phamacokinetics of a single oral dose of dihydroartemisinin in Vietnamese healthy volunteers

Pharmacokinetics of a 240 mg single dose of oral dihydroartemisinin (DHA) was investigated in 8 healthy (5 males, 3 females) Vietnamese volunteers. Plasma concentrations were measured by high-performance liquid chromatography with electrochemical detection in the reductive mode. The concentration time profile of DHA was fitted with one-compartment model with a lag time. Pharmacokinetics of DHA is comparable between males and females even when adjusted with dosage. The median (range) values of pooled pharmacokinetics of oral DHA were: t(lag) 0.41 (0.09-0.78) hours, t(1/2z) 0.58 (0.17-1.43) hours, t(max) 1.6 (1.1-2.2) hours, Cmax 466 (128-787) ng/ml. Cmax/dosage 97.7 (27.2-124.6) ng/ml, t(1/2z) 2.0 (1.5-3.4) hours, AUC 1867 (420-3535) ng x h/ml, AUC/dosage 364.3 (89.3-559.7) ng x h/ml/dosage, Cl/f 45.8 (30.0-190.0) ml/min/kg, Vz/f 8.0 (5.5-29.9) l/kg. Interindividual variation was large, the coefficients of variation (CV) were 47.8% and 45.3% respectively to AUC and Cmax. The t(max) of DHA formulation was comparable with that of DHA metabolite of artemisinin derivatives. The t(1/2z) was longer and shorter than that of DHA metabolites of oral formulations of artesunate and artemether, respectively. For monotherapeutic regimen(s) of DHA, dosing frequency of at least twice a day is suggested. Combined regimen(s) of DHA with other potent, long half-life antimalarials may also be an alternative approach.     

Ex vivo blood schizontocidal activities of artemisinin derivatives against Plasmodium falciparum

Serum samples collected at intervals from eight healthy volunteers after the administration of the six regimens of artemisinin derivatives were investigated for their ex vivo blood schizontocidal activities against K1 strain Plasmodium falciparum. The regimens included single doses of (a) 300 mg oral artemether; (b) 300 mg intramuscular artemether; (c) 100 mg suppository artemether; (d) 300 mg oral artesunate (Guillin formulation); (e) 300 mg oral artesunate (Arenco formulation); (f) 300 mg oral dihydroartemisinin. Sera collected after various regimens of artemisinin derivatives showed distinct degree of ex vivo blood schizontocidal activities. Activity of sera after suppository dosing was remarkably low and variable comparing to the other two formulations (oral, intramuscular). Median values for Amax (the maximum activity normalized with dose) of sera from oral dosing were 2.4- and 118-fold, while AUA (the area under activity-time curve, normalized with dose) were 0.82- and 2,370-fold of that after the intramuscular and suppository dosing, respectively. Sera from artesunate-Arenco dosing exhibited significantly higher Amax and AUA (medians: Amax 12.4 vs 5.13 nmol/l/mg dose; AUA: 21.9 vs 8.8 nmol x h/ml/mg dose), compared to that from artesunate-Guillin dosing. Among the oral formulations of artemisinin derivatives investigated (artemether, artesunate, dihydroartemisinin), sera collected following a single dose of oral dihydroartemisinin exhibited lowest bioactivity (Amax 2.35 nmol/l/mg dose; AUA: 44 nmol x h/ml/mg dose).     

Investigation of the in vitro Gender-Specific Partitioning of Mefloquine in Malarial Infected Red Blood Cells and Plasma

The investigation of gender-specific partitioning of the antimalarial drug mefloquine to cellular and fluid blood compartments was performed using blood collected from a female and male healthy subject that were infected with Plasmodium falciparum PCM2 clone and spiked with mefloquine (0.25, 1, and 5 μM). Mefloquine concentrations in red cells of both female and male subjects were significantly higher than plasma, which suggests an intensive uptake by red cells. This was supported by a high ratio of mefloquine concentrations in the parasitized and non-parasitized red cells of about 4-fold. Gender-specific partitioning of mefloquine in parasitized blood was seen only in plasma where significantly higher concentrations were observed in female compared with male plasma. Down-adjusting the therapeutic dose of mefloquine in female patients with malaria is not advisable because mefloquine concentrations in the target cellular compartment are similar in both genders.     

Evaluation of Plasmodium vivax isolates in Thailand using polymorphic markers Plasmodium merozoite surface protein (PvMSP) 1 and PvMSP3

Parasitology Research - Malaria is a significant public health problem in several tropical countries including Thailand. The prevalence of Plasmodium vivax infection has been increasing in the past...     

Pharmacokinetics of a five-day oral dihydroartemisinin monotherapy regimen in patients with uncomplicated falciparum malaria

The pharmacokinetics of dihydroartemisinin (DHA) in a 5-day oral monotherapy regimen was investigated in ten adult Vietnamese patients with uncomplicated falciparum malaria. The patients were treated with a total dose of 900 mg DHA divided as single daily doses of 300, 300, 100, 100, and 100 mg from day 0 through day 4. There were no differences in the concentrations of DHA within the first two days of treatment. The pharmacokinetics of DHA in the acute phase, however, was significantly different from that in the convalescent phase of malaria. Reduced half-life (T(1/2z)) and lower area under concentration curve (AUC(infinity)) values were observed on the final day of treatment in comparison to those obtained on the first day. These decreases in T(1/2z) and AUC(infinity) were observed in concordance with increased drug clearance (CL/F). Furthermore, the time required to reach maximum plasma DHA concentration (T(max)) on day 4 was shorter than that on day 0. Together, these findings suggest that the change in pharmacokinetics of DHA is related to the physiological change in malaria patients between the acute and convalescent phases of the disease.     

Ultrasonography as a tool for monitoring the development and progression of cholangiocarcinoma in Opisthorchis viverrini/ dimethylnitrosamine-induced hamsters

Cholangiocarcinoma (CCA) is the most common cancer in northeastern Thailand. At present, effective diagnosis of CCA either in humans or animals is not available. Monitoring the development and progression of CCA in animal models is essential for research and development of new promising chemotherapeutics. Ultrasonography has been widely used for screening of bile duct obstruction in CCA patients. In this study, we preliminarily investigated the applicability of ultrasonography to monitor the development and progression of CCA in Syrian golden hamsters (n=8) induced by Opisthorchis viverrini (OV)/dimethylnitrosamine (DMN) administration. Ultrasonography and histopathological examination of hamsters was performed at week 0, 20, 24 and 28 of OV infection or at the start of water/Tween-80 administration to controls. The ultrasonographic images of liver parenchyma and gallbladders of OV/DMN-induced CCA hamsters showed sediments in gallbladder, thickening of gallbladder wall, and hypoechogenicity of liver parenchyma cells. The ultrasonographic images of liver tissues were found to correlate well with histopathological examination. Although ultrasonography does not directly detect the occurrence of CCA, it reflects the thickening of bile ducts and abnormality of liver tissues. It may be applied as a reliable tool for monitoring the development and progression of CCA in animal models in research and development of new promising chemotherapeutics for CCA.     

Trigenomic origin of the hexaploid Psammopyrum athericum (Triticeae: Poaceae) revealed by in-situ hybridization

The genomic constitution of the hexaploid Psammopyrum athericum was studied with in-situ DNA hybridization using both genomic DNA and isolated cloned sequences as probes. A genomic probe from Thinopyrum bessarabicum (E genome) hybridized successfully to 14 chromosomes of Ps. athericum and a probe from Festucopsis serpentinii (L genome) hybridized to another 14 chromosomes. The remaining chromosomes did not hybridize, apart from in the centromeric region, to any of the genomic probes used. It is thus proposed that Ps. athericum contains the genomes E, L and X where X stands for a so-far unknown genome. Psammopyrum athericum has three pairs of pTa71 sites and approximately 30 pSc119:2 sites. The origin of the third genome will be a matter for further research using genomic and genome-specific probes.     

Polymorphic patterns of pfcrt and pfmdr1 in Plasmodium falciparum isolates along the Thai-Myanmar border

Objective

To investigate the distribution and patterns of pfcrt and pfmdr1 polymorphisms in Plasmodium falciparum (P. falciparum) isolates collected from the malaria endemic area of Thailand along Thai-Myanmar border.

Methods

Dried blood spot samples were collected from 172 falciparum malaria patients prior received treatment. The samples were extracted using chelex to obtain parasite DNA. PCR-RFLP was employed to detect pfcrt mutation at codons 76, 220, 271, 326, 356 and 371, and the pfmdr1 mutation at codon 86. Pfmdr1 gene copy number was determined by SYBR Green I real-time PCR.

Results

Mutant alleles of pfcrt and wild type allele of pfmdr1 were found in almost all samples. Pfmdr1 gene copy number in isolates collected from all areas ranged from 1.0 to 5.0 copies and proportion of isolates carrying>1 gene copies was 38.1%. The distribution and patterns of pfcrt and pfmdr1 mutations were similar in P. falciparum isolates from all areas. However, significant differences in both number of pfmdr1 copies and prevalence of isolates carrying>1 gene copies were observed among isolates collected from different areas. The median pfmdr1 copy number in P. falciparum collected from Kanchanaburi and Mae Hongson were 2.5 and 2.0, respectively and more than half of the isolates carried>1 gene copies.

Conclusions

The observation of pfmdr1 wild type and increasing of gene copy number may suggest declining of artesunate-mefloquine treatment efficacy in P. falciparum isolates in this border area.     

Inhibitory activities of plumbagin on cell migration and invasion and inducing activity on cholangiocarcinoma cell apoptosis

Objective: To investigate the cytotoxic, apoptotic and inhibitory activities on cell migration and invasion of plumbagin in the human cholangiocarcinoma(CCA) cell line(CL-6) in comparison with human embryonic fibroblast cell line(OUMS). Methods: Cytotoxicity activity was evaluated using MTT assay. Inhibitory effect on cell migration and invasion were investigated using label-free real-time cell analysis and QCM ECMatrix cell invasion chamber, respectively. Apoptotic activity was evaluated using flow cytometry and Cell Event? Caspase 3/7 assay. Results: Based on results of the cytotoxicity test in CL-6 cells, 50% inhibitory concentration(IC_(50), Mean±SD) values of plumbagin and the standard drug 5-fluorouracil were(24.00±3.33) and(1 036.00±137.77) μmol/L, respectively. The corresponding values for OUMS cells were(57.00±5.23) and(2 147.00±209.98) μmol/L, respectively. The selectivity index was 2.28. The inhibitory activities of plumbagin on cell migration and invasion were potent and concentration-dependent with IC_(50) of 25.0 μmol/L and complete inhibition at 25.0 μmol/L. Flow cytometry analysis showed that plumbagin at 12.5 μmol/L(half IC_(50)) induced CL-6 cell apoptosis(43.24% of control) through stimulation of caspase 3/7 activities. Complete cell apoptosis was observed at 12.5 μmol/L. Conclusions: The cytotoxic activity and inhibition of migration and invasion including apoptosis induction in the human CCA cell line(CL-6) suggest that plumbagin could be a promising candidate for CCA chemotherapeutics. However, its relatively low selective cytotoxic effect on CCA cells is a major concern.