Concentrations Of Dihydroartemisinin Research Articles

Population Pharmacokinetics of Artemether, Lumefantrine, and Their Respective Metabolites in Papua New Guinean Children with Uncomplicated Malaria

There are sparse published data relating to the pharmacokinetic properties of artemether, lumefantrine, and their active metabolites in children, especially desbutyl-lumefantrine. We studied 13 Papua New Guinean children aged 5 to 10 years with uncomplicated malaria who received the six recommended doses of artemether (1.7 mg/kg of body weight) plus lumefantrine (10 mg/kg), given with fat over 3 days. Intensive blood sampling was carried out over 42 days. Plasma artemether, dihydroartemisinin, lumefantrine, and desbutyl-lumefantrine were assayed using liquid chromatography-mass spectrometry or high-performance liquid chromatography. Multicompartmental pharmacokinetic models for a drug plus its metabolite were developed using a population approach that included plasma artemether and dihydroartemisinin concentrations below the limit of quantitation. Although artemether bioavailability was variable and its clearance increased by 67.8% with each dose, the median areas under the plasma concentration-time curve from 0 h to infinity (AUC(0-∞)s) for artemether and dihydroartemisinin (3,063 and 2,839 μg · h/liter, respectively) were similar to those reported previously in adults with malaria. For lumefantrine, the median AUC(0-∞) (459,980 μg · h/liter) was also similar to that in adults with malaria. These data support the higher dose recommended for children weighing 15 to 35 kg (35% higher than that for a 50-kg adult) but question the recommendation for a lower dose in children weighing 12.5 to 15 kg. The median desbutyl-lumefantrine/lumefantrine ratio in the children in our study was 1.13%, within the range reported for adults and higher at later time points because of the longer desbutyl-lumefantrine terminal elimination half-life. A combined desbutyl-lumefantrine and lumefantrine AUC(0-∞) weighted on in vitro antimalarial activity was inversely associated with recurrent parasitemia, suggesting that both the parent drug and the metabolite contribute to the treatment outcome of artemether-lumefantrine.

Exploring the autophagy of glioma cells induced by dihydroartemisinin in vitro

Objective To investigate the anti -glioma efficacy of dihydroartemisinin (DHA) and combined with temozolomide (TMZ) on human glioma cell line in vitro.Methods The growth inhibition of DHA on 10 glioma cell lines induced by DHA treatment for 72 h was analyzed by MTT method.TMZ combined with 0.5 μg/ml DHA,and the IC5o value was measured in SKMG -4 cells.The autofluorescent drug monodansylcadaverine (MDC) was used to mark autophagicvacuoles.The autophagy related protein LC3 - B and Beclin - 1,and the apoptosis protein caspase - 3 were analyzed by western blot (WB).Results The IC50 of DHA was different in ten glioma cell lines [ from ( 1.17 ± 0.078 ) μg/ml to (23.568±0.796) μg/ml].In SKMG -4 cells,the autophagicvacuoles were detected in the DHA group,the IC50 of TMZ had significant difference with 0.5 μg/ml DHA contrast to the control group ( P ＜ 0.01 ),and the levels of LC3 - B and Beclin - 1 protein were increased gradually with the increase of DHA concentration,and caspase -3 protein has no difference.Conclusion DHA can inhibit proliferation of glioma cell lines and increase the efficacy of TMZ,and the autophagy may be the mechanism. Key words: Glioma ; Autophagy ; Dihydroartemisinin ; Temozolomide ;

Topical dihydroartemisinin inhibits suture-induced neovascularization in rat corneas through ERK1/2 and p38 pathways.

To determine if topical instillation of dihydroartemisinin (DHA) inhibits corneal neovascularization (NV) in rats and to investigate the role of the extracellular regulated kinases (ERK) 1/2 and p38 pathways in this process. Suture-induced corneal NV was produced in rats and the eyes were topically treated with different concentrations of DHA (20mg/L, 10mg/L or 5mg/L) or normal saline 4 times a day for 7 days. The corneal NV was quantified as the proportion of NV area to the whole cornea. Western blot was used to determine the expressions of vascular endothelial growth factor (VEGF) and the phosphorylation status of VEGF receptor-2, ERK1/2 and p38 in the corneas. Immunofluorescent staining was used to determine the expressions of phospho-ERK1/2 and phospho-p38 in the corneal tissues from the eyes treated with 20 mg/L DHA (DHA group) or normal saline (control group). The proportion of corneal NV area in the eyes treated with normal saline or DHA at dosages of 20mg/L, 10mg/L or 5mg/L was (23.74±3.00)%, (15.73±2.88)%, (19.53±2.42)%, and (23.38±2.79)%, respectively. In the eyes treated with 20mg/L or 10mg/L DHA, the corneal NV area was significantly reduced when compared to that in eyes with normal saline (P<0.05). Western blot analyses revealed that 20mg/L DHA significantly inhibited the expressions of VEGF and phospho-VEGFR-2. Both 20mg/L and 10mg/L DHA inhibited the expressions of phospho-ERK1/2 and phospho-p38. Immunofluorescent staining further demonstrated that 20mg/L DHA lowered the expression levels of phospho-ERK1/2 and phospho-p38 in the corneas with suture-induced NV. Suture-induced NV in rat corneas was significantly inhibited by topical treatment with 20mg/L and 10mg/L DHA. The results suggest that the effects could be partially dependent on the DHA-mediated inhibitions of the ERK1/2 and p38 pathways.

Anti-tumor effects of dihydroartemisinin on human osteosarcoma

Dihydroartemisinin (DHA) exhibits antitumor activity against a wide spectrum of cancer cells. However, whether DHA has anti-tumor effect on human osteosarcoma cells remains unknown. This study aims to investigate the anti-tumor activity of DHA and the underlying mechanisms in human osteosarcoma cell lines with different p53 mutation statuses. Four human osteosarcoma cell lines were treated with different concentrations of DHA. Then, cell proliferation was determined by the CCK-8 viability assay; apoptosis and cell cycle progression were evaluated by flow cytometry; protein expression was analyzed by western blot assay; and NF-kB activity was examined by luciferase assay. The results demonstrated that DHA treatment could inhibit the proliferation of four osteosarcoma cell lines in a dose-dependent manner. P53 wild-type osteosarcoma cells were more sensitive to DHA. Moreover, the percentage of apoptotic cell and cell arrest in G₂/M phase was increased upon DHA treatment in a dose-dependent manner. Mechanistically, DHA activated caspase-3, caspase-8, and caspase-9; upregulated the expression of Bax, FAS, and cyclin D1; downregulated the expression of Bcl-2, Cdc25B, and cyclin B1; and inhibited the activity of NF-кB. In conclusion, DHA has significant anticancer effects against human osteosarcoma cells, which include induction of apoptosis and cell cycle arrest. The p53 gene may play a certain role in the DHA-induced human osteosarcoma apoptosis and cell cycle arrest. DHA is a novel anti-osteosarcoma drug candidate that merits further study.

Artemisinin Resistance in Cambodia: A Clinical Trial Designed to Address an Emerging Problem in Southeast Asia

Increasing rates of failure of artemisinin-based combination therapy have highlighted the possibility of emerging artemisinin resistance along the Thai-Cambodian border. We used an integrated in vivo-in vitro approach to assess the presence of artemisinin resistance in western Cambodia. This article provides additional data from a clinical trial that has been published in The New England Journal of Medicine. Ninety-four adult patients from Battambang Province, western Cambodia, who presented with uncomplicated falciparum malaria were randomized to receive high-dose artesunate therapy (4 mg/kg/day orally for 7 days) or quinine-tetracycline. Plasma concentrations of dihydroartemisinin, in vitro drug susceptibility, and molecular markers were analyzed. Cases meeting all the following criteria were classified as artemisinin resistant: failure to clear parasites within 7 days of treatment or reemergence of parasites within 28 days of follow-up; adequate plasma concentrations of dihydroartemisinin; prolonged parasite clearance; and increased in vitro drug susceptibility levels for dihydroartemisinin. Two (3.3%) of 60 artesunate-treated patients were classified as artemisinin resistant. Their parasite clearance times were prolonged (133 and 95 h, compared with a median of 52.2 h in patients who were cured). These patients had 50% inhibitory concentrations of dihydroartemisinin that were almost 10 times higher than the reference clone W2. Resistance did not appear to be mediated by the pfmdr1 copy number or selected PfATPase6 polymorphisms previously proposed to confer artemisinin resistance. Artemisinin resistance has emerged along the Thai-Cambodian border. The potentially devastating implications of spreading resistance to a drug that currently has no successor call for further studies of this emerging problem. ClinicalTrials.gov identifier NCT00479206.

Declining in efficacy of a three-day combination regimen of mefloquine-artesunate in a multi-drug resistance area along the Thai-Myanmar border

BackgroundDeclining in clinical efficacy of artesunate-mefloquine combination has been documented in areas along the eastern border (Thai-Cambodian) of Thailand. In the present study, the clinical efficacy of the three-day combination regimen of artesunate-mefloquine as first-line treatment for acute uncomplicated falciparum malaria in Thailand was monitored in an area along the western border (Thai-Myanmar) of the country.MethodsA total of 150 Burmese patients (85 males and 65 females) aged between 16 and 50 years who were attending the Mae Tao clinic, Mae-Sot, Tak Province, and presenting with symptomatic acute uncomplicated Plasmodium falciparum malaria were included into the study. Patients were treated initially (day 0) with 4 mg/kg body weight artesunate and 15 mg/kg body weight mefloquine. The dose regimen on day 2 was 4 mg/kg body weight artesunate and 10 mg/kg body weight mefloquine. On day 3, artesunate at the dose of 4 mg/kg body weight was given with 0.6 mg/kg body weight primaquine. Whole blood mefloquine and plasma artesunate and dihydroartemisinin (active plasma metabolite of artesunate) concentrations following treatment were determined by high performance liquid chromatography (HPLC) and liquid chromatography-mass spectrometry (LCMS), respectively.ResultsThirty-four cases had recrudescence during days 7 and 42. Five and 5 cases, respectively had reinfection with P. falciparum and reappearance of Plasmodium vivax in their peripheral blood during follow-up. The Kaplan-Meier estimate of the 42-and 28-day efficacy rates of this combination regimen were 72.58% (95% CI: 63.20-79.07%) and 83.06 (95% CI 76.14-94.40%), respectively. Parasite clearance time (PCT) and fever clearance time (FCT) were significantly prolonged in patients with treatment failure compared with those with sensitive response [median (95% CI) values for PCT 32.0 (20.0-48.0) vs 24.0 (14.0-32.0) hr and FCT 30.0 (22.0-42.0) vs 26.0 (18.0-36.0) hr; p < 0.005]. Whole blood mefloquine concentrations on days 1, 7 and 14 in patients with sensitive and recrudescence response were comparable. Although plasma concentration of dihydroartemisinin at 1 hour of treatment was significantly lower in patients with recrudescence compared with sensitive response [mean (95% CI) 456 (215-875) vs 525 (452-599) ng/ml; p < 0.001], the proportion of patients with recrudescence who had relatively low (compared with the lower limit of 95% CI defined in the sensitive group) was significantly smaller than that of the sensitive group.ConclusionsAlthough pharmacokinetic (ethnic-related) factors including resistance of P. falciparum to mefloquine contribute to some treatment failure following treatment with a three-day combination regimen of artesunate-mefloquine, results suggest that artesunate resistance may be emerging at the Thai-Myanmar border.

Early clinical development of artemether-lumefantrine dispersible tablet: palatability of three flavours and bioavailability in healthy subjects

BackgroundEfforts to ease administration and enhance acceptability of the oral anti-malarial artemether-lumefantrine (A-L) crushed tablet to infants and children triggered the development of a novel dispersible tablet of A-L. During early development of this new formulation, two studies were performed in healthy subjects, one to evaluate the palatability of three flavours of A-L, and a second one to compare the bioavailability of active principles between the dispersible tablet and the tablet (administered crushed and intact).MethodsStudy 1 was performed in 48 healthy schoolchildren in Tanzania. Within 1 day, all subjects tasted a strawberry-, orange- and cherry-flavoured oral A-L suspension for 10 seconds (without swallowing) in a randomized, single-blind, crossover fashion. The palatability of each formulation was rated using a visual analogue scale (VAS). Study 2 was an open, randomized crossover trial in 48 healthy adults given single doses of A-L (80 mg artemether + 480 mg lumefantrine) with food. The objectives were to compare the bioavailability of artemether, dihydroartemisinin (DHA) and lumefantrine between the dispersible tablet and the tablet administered crushed (primary objective) and intact (secondary objective).ResultsStudy 1 showed no statistically significant difference in VAS scores between the three flavours but cherry had the highest score in several ratings (particularly for overall liking). Study 2 demonstrated that the dispersible and crushed tablets delivered bioequivalent artemether, DHA and lumefantrine systemic exposure (area under the curve [AUC]); mean ± SD AUC0-tlast were 208 ± 113 vs 195 ± 93 h.ng/ml for artemether, 206 ± 81 vs 199 ± 84 h.ng/ml for DHA and 262 ± 107 vs 291 ± 106 h.μg/ml for lumefantrine. Bioequivalence was also shown for peak plasma concentrations (Cmax) of DHA and lumefantrine. Compared with the intact tablet, the dispersible tablet resulted in bioequivalent lumefantrine exposure, but AUC and Cmax values of artemether and DHA were 20-35% lower.ConclusionsConsidering that cherry was the preferred flavour, and that the novel A-L dispersible tablet demonstrated similar pharmacokinetic performances to the tablet administered crushed, a cherry-flavoured A-L dispersible tablet formulation was selected for further development and testing in a large efficacy and safety study in African children with malaria.

Population pharmacokinetics and pharmacodynamics of artemether and lumefantrine during combination treatment in children with uncomplicated falciparum malaria in Tanzania.

The combination of artemether (ARM) and lumefantrine is currently the first-line treatment of uncomplicated falciparum malaria in mainland Tanzania. While the exposure to lumefantrine has been associated with the probability of adequate clinical and parasitological cure, increasing exposure to artemether and the active metabolite dihydroartemisinin (DHA) has been shown to decrease the parasite clearance time. The aim of this analysis was to describe the pharmacokinetics and pharmacodynamics of artemether, dihydroartemisinin, and lumefantrine in African children with uncomplicated malaria. In addition to drug concentrations and parasitemias from 50 Tanzanian children with falciparum malaria, peripheral parasite densities from 11 asymptomatic children were included in the model of the parasite dynamics. The population pharmacokinetics and pharmacodynamics of artemether, dihydroartemisinin, and lumefantrine were modeled in NONMEM. The distribution of artemether was described by a two-compartment model with a rapid absorption and elimination through metabolism to dihydroartemisinin. Dihydroartemisinin concentrations were adequately illustrated by a one-compartment model. The pharmacokinetics of artemether was time dependent, with typical oral clearance increasing from 2.6 liters/h/kg on day 1 to 10 liters/h/kg on day 3. The pharmacokinetics of lumefantrine was sufficiently described by a one-compartment model with an absorption lag time. The typical value of oral clearance was estimated to 77 ml/h/kg. The proposed semimechanistic model of parasite dynamics, while a rough approximation of the complex interplay between malaria parasite and the human host, adequately described the early effect of ARM and DHA concentrations on the parasite density in malaria patients. However, the poor precision in some parameters illustrates the need for further data to support and refine this model.

Simultaneous Determination of Artesunate and Dihydroartemisinin Concentrations in Human Plasma by High Performance Liquid Chromatography-Mass Spectrometry with Electro-Spray Ionization

An analytical procedure was developed/validated for the quantification of artesunate (ARTS) and a metabolite, dihydroartemisinin (DHA), in human plasma. Plasma samples were processed by solid-phase extraction and analyzed by LC-MS. The detector response was specific and linear for ARTS and DHA concentrations in the range of 5–1000 ng/mL. Intra-/inter-day precision/accuracy were determined to be within the acceptance criteria for assay validation guidelines. The analytes were stable under various processing/handling conditions. The ARTS/DHA concentrations were readily measured in plasma samples up to 8 hrs after an oral administration of an ARTS formulation in humans, suggesting that the assay is practically useful.

Atorvastatin as a Potential Antimalarial Drug: In Vitro Synergy in Combinational Therapy with Dihydroartemisinin

Atorvastatin (AVA) is a synthetic inhibitor of 3-hydroxy-3-methylglutaryl-coenzyme A. AVA has lipid-lowering ability, a long plasma half-life, and an excellent safety record. In addition to the previously mentioned positive aspects of AVA, this drug has also shown in vitro antimalarial activity (10). AVA showed no in vitro cross-resistance with the commonly used antimalarials. In addition, the 50% inhibitory concentrations (IC50s) of AVA were found to be unrelated to mutations occurring in transport protein genes involved in quinoline antimalarial drug resistance, including the pfcrt, pfmdr1, pfmrp, and pfnhe-1 genes (8). Nevertheless, AVA treatment alone, at a dose of 20 mg/kg of body weight, failed to prevent death due to cerebral malaria and was not able to affect parasitemia in infected mice (1). One possibility is that AVA could act as an adjuvant therapy. Wong and Davis recently showed that AVA did not potentiate the in vitro activity of dihydroartemisinin (DHA) in the 3D7 strain of P. falciparum (13) and also posited that AVA had no clinical relevance because AVA IC50s were well above the plasma concentrations achievable in humans taking high-dose AVA (0.1 to 0.5 μM) (2). In the present study, we tested the effects of AVA at six concentrations (0.1, 0.5, 1, 2, 4, and 8 μM). We used 13 well-established strains of P. falciparum for the analysis (Table ​(Table1)1) (6). The methodology of the in vitro potentiation test was previously described (5). The combination of AVA and DHA had synergistic effects (Fig. ​(Fig.1).1). The differences in DHA IC50 between AVA concentrations groups have first been tested using analysis of variance for repeated measures to take into account the fact that observations made within each strain were not independent. Using the most conservative correction for interdependence between observations (i.e., Box's conservative epsilon), the differences in DHA IC50 were highly significant (P < 0.001) in the range of AVA plasma concentrations achievable in patients taking 80 mg of AVA daily (Table ​(Table1).1). Using a random-effect linear regression approach, the regression coefficients for the log-transformed DHA IC50 indicated that the mean fold change in the DHA IC50 when adding AVA at concentrations of 0.1, 0.5, and 1.0 μM (0.90, 0.82, and 0.72, respectively) were also highly significant (P < 0.001). The DHA IC50 was reduced by 10% (range, 0 to 24%; 95% confidence interval [CI], 5 to 15%), 18% (range, 8 to 38%; 95% CI, 14 to 22%), and 28% (range, 15 to 43%; 95% CI, 24 to 32%) in the presence of AVA at concentrations of 0.1, 0.5, and 1.0 μM, respectively. These reductions were all significant (P < 0.001). Another finding was that the synergy of the effects of DHA was AVA dose dependent. The reductions in DHA IC50 were also significant (P < 0.001) between 0.1 and 0.5 μM AVA and between 0.5 and 1.0 μM AVA. FIG. 1. In vitro synergy of AVA with DHA against 13 strains of P. falciparum. TABLE 1. In vitro susceptibilities of 13 P. falciparum strains to AVA alone, DHA alone, and combinations of DHA and different concentrations of AVA In contrast to previously published studies on 3D7 (13), we showed that AVA had a synergistic effect on DHA activity. These controversial findings could be explained by differences in the isotopic method used; Wrong and Davis used a modified microdilution isotopic method with 50% plasma (versus 10% in commonly used in vitro test). In addition, their IC50 of DHA alone was 12.5 nM, while the commonly accepted IC50 on 3D7 was <4 nM. We also illustrated that this synergy occurred at AVA plasma concentrations achievable in patients taking 80 mg of AVA daily (0.1 to 0.5 μM) (2). Furthermore, the doses of AVA administered to humans could be increased to 120 mg daily with only limited additional side effects (9). A dose of 120 mg of AVA increased the maximal plasma concentration (Cmax) after oral administration by 4- to 10-fold. Cerebral malaria has pathophysiological features in common with sepsis, especially with regard to the pathology of the endothelium (4), and critically ill patients with sepsis had a significantly higher Cmax than healthy volunteers (110.5 versus 5.9 ng/ml) (7). Artemisinin-based combination therapy is beginning to fail in southern Cambodia and Thailand, particularly the mefloquine-artesunate drug combination (3, 11, 12). AVA could improve the activity of artemisinin derivatives. All of these observations support calls for both an in vivo evaluation with a pharmacokinetic component and clinical trials of AVA as an antimalarial therapy.

Pharmacokinetic Profiles of Artesunate After Single Intravenous Doses at 0.5, 1, 2, 4, and 8 mg/kg in Healthy Volunteers: A Phase I Study

The pharmacokinetics of good manufacturing process injection of artesunate (AS) were evaluated after single doses at 0.5, 1, 2, 4, and 8 mg/kg with a 2-minute infusion in 40 healthy subjects. Drug concentrations were analyzed by validated liquid chromatography and mass spectrometry system (LC-MS/MS) procedures. The drug was immediately converted to dihydroartemisinin (DHA), with elimination half-lives ranging 0.12-0.24 and 1.15-2.37 hours for AS and DHA, respectively. Pharmacokinetic model-dependent analysis is suitable for AS, whereas DHA fits both model-dependent and -independent methods. Although DHA concentration was superior to that of AS with a 1.12-1.87 ratio of area under the curve (AUC)(DHA/AS), peak concentration of AS was much higher than that of DHA, with a 2.80- to 4.51-fold ratio of peak concentration (C(max AS/DHA)). Therefore, AS effectiveness has been attributed not only to its rapid hydrolysis to DHA, but also to itself high initial C(max).

Population pharmacokinetics of artesunate and amodiaquine in African children.

BackgroundPharmacokinetic (PK) data on amodiaquine (AQ) and artesunate (AS) are limited in children, an important risk group for malaria. The aim of this study was to evaluate the PK properties of a newly developed and registered fixed dose combination (FDC) of artesunate and amodiaquine.MethodsA prospective population pharmacokinetic study of AS and AQ was conducted in children aged six months to five years. Participants were randomized to receive the new artesunate and amodiaquine FDC or the same drugs given in separate tablets. Children were divided into two groups of 70 (35 in each treatment arm) to evaluate the pharmacokinetic properties of AS and AQ, respectively. Population pharmacokinetic models for dihydroartemisinin (DHA) and desethylamodiaquine (DeAq), the principal pharmacologically active metabolites of AS and AQ, respectively, and total artemisinin anti-malarial activity, defined as the sum of the molar equivalent plasma concentrations of DHA and artesunate, were constructed using the non-linear mixed effects approach. Relative bioavailability between products was compared by estimating the ratios (and 95% CI) between the areas under the plasma concentration-time curves (AUC).ResultsThe two regimens had similar PK properties in young children with acute malaria. The ratio of loose formulation to fixed co-formulation AUCs, was estimated as 1.043 (95% CI: 0.956 to 1.138) for DeAq. For DHA and total anti-malarial activity AUCs were estimated to be the same. Artesunate was rapidly absorbed, hydrolysed to DHA, and eliminated. Plasma concentrations were significantly higher following the first dose, when patients were acutely ill, than after subsequent doses when patients were usually afebrile and clinically improved. Amodiaquine was converted rapidly to DeAq, which was then eliminated with an estimated median (range) elimination half-life of 9 (7 to 12) days. Efficacy was similar in the two treatments groups, with cure rates of 0.946 (95% CI: 0.840–0.982) in the AS+AQ group and 0.892 (95% CI: 0.787 – 0.947) in the AS/AQ group. Four out of five patients with PCR confirmed recrudescences received AQ doses < 10 mg/kg. Both regimens were well tolerated. No child developed severe, post treatment neutropaenia (<1,000/μL). There was no evidence of AQ dose related hepatotoxicity, but one patient developed an asymptomatic rise in liver enzymes that was resolving by Day-28.ConclusionThe bioavailability of the co-formulated AS-AQ FDC was similar to that of the separate tablets for desethylamodiaquine, DHA and the total anti-malarial activity. These data support the use this new AS-AQ FDC in children with acute uncomplicated falciparum malaria.

Absence of time-dependent artesunate pharmacokinetics in healthy subjects during 5-day oral administration

The aim of the present study was to investigate the existence of time-dependent pharmacokinetics of artesunate (ARS) during 5 consecutive days of oral administration to 10 healthy Vietnamese subjects (aged 21-52 years and weighing 49-90 kg). Each volunteer received 200 mg oral doses of ARS once daily for 5 consecutive days. Blood samples (3 ml each) were collected on days 1 and 5 at 0 (before dosing), 0.5, 1, 2, 3, 4, and 6 h after drug administration. During days 2, 3, and 4, the same volumes of blood were collected at 0, 1, 2, and 4 h after dosing. Plasma ARS and dihydroartemisinin (DHA) were measured using high-performance liquid chromatography-mass spectrometry (LC-MS). Results did not show evidence of time-dependency for ARS or the active plasma metabolite DHA. There were no differences in the concentrations of ARS and DHA at all sampling times on days 1 and 5. In addition, the pharmacokinetics of both compounds were similar on days 1 and 5. This finding confirms that the enzyme auto-induction in drug metabolism may not be characteristic of the endoperoxide sesquiterpene antimalarial group.

Pharmacokinetic and Pharmacodynamic Evaluation of Intramuscular Artesunate in Healthy Beagle Dogs

Pharmacokinetic and pharmacodynamic responses were evaluated after intramuscular (i.m.) injection of artesunate (AS). Twelve dogs were injected with i.m. AS at 2.5, 5, or 10 mg/kg into the left gluteal muscle. A second injection of only diluent was given in the right gluteal muscle. At 24 hours post-injection, plasma creatine kinase (CK) concentrations were elevated above normal. Muscle biopsies showed myocyte necrosis and acute inflammation, which was worse on the treated side. At 7 days after injection, CK concentrations were normal. Muscle biopsies showed mineralization, fibrosis, and chronic inflammation with less difference between sides. Compared with intravenous administration, i.m. AS resulted in a prolonged half-life for both AS and DHA. Intramuscular AS also had a lower mean dose-adjusted C(max) and a higher mean dose-adjusted area under the curve; but produced similar concentrations of dihydroartemisinin. These findings suggest that adverse reactions to i.m. artesunate are minor and temporary which justify further study of this route in treating severe malaria.

Pharmacokinetics of artesunate in the domestic pig

The aim was to study the pharmacokinetic profile of artesunate and its metabolite dihydroartemisinin (DHA) in a pig model. Thirteen pigs received either intravenous (iv) or intramuscular (im) artesunate (60 mg), with the alternative preparation given 24 h later in an open crossover design. Five of them also received an additional intra-arterial (ia) artesunate dose (60 mg). The plasma concentrations of artesunate and DHA were determined by high-performance liquid chromatography with electrochemical detection. Population modelling was performed with NONMEM, using a two-compartment model. Plasma concentration-time profiles were comparable to those observed in humans, with a rapid and biphasic decline for both artesunate and DHA. Following an iv bolus, artesunate had a median maximum plasma concentration (C(max)) of 13.8 microM [interquartile range (IQR), 10.4-22.1 microM], elimination half-life (t(1/2)) = 18 min (IQR, 16-22 min), total plasma clearance (CL) = 5.58 L/h/kg (IQR, 3.31-5.91 L/h/kg) and volume of distribution (V(d)) = 1.85 L/kg (IQR, 1.27-3.20 L/kg). The median C(max) value for DHA was 3.30 microM (IQR, 2.08-5.95 microM), t(1/2) = 26 min (IQR, 23-31 min), CL/Fm = 4.37 L/h/kg (IQR, 3.29-6.87 L/h/kg) and V(d)/Fm = 2.56 L/kg (IQR, 1.93-4.49 L/kg). Artesunate and DHA pharmacokinetic parameters were similar after ia administration. Following im dosing, median artesunate C(max) was 4.81 microM (IQR, 3.74-5.40 microM), t(1/2) = 18 min (IQR, 16-28 min), CL = 4.37 L/h/kg (IQR, 4.13-4.68 L/h/kg) and V(d) = 2.07 L/kg (IQR, 1.83-2.79 L/kg); the bioavailability was 100%. For DHA, median C(max) was 1.43 microM (IQR, 1.00-1.92 microM), t(1/2) = 27 min (IQR, 25-37 min), CL/Fm = 4.68 L/h/kg (IQR, 3.35-6.73 L/h/kg) and V(d)/Fm = 3.31 L/kg (IQR, 2.89-4.27 L/kg). The pharmacokinetic properties of artesunate and DHA in pigs were similar to those reported in humans, suggesting that the swine model is suitable for determining the preclinical pharmacokinetics of artemisinin derivatives.

Dihydroartemisinin Potentiates the Cytotoxic Effect of Temozolomide in Rat C6 Glioma Cells

Gliomas are the most common primary brain tumor in adults, but the efficacy of chemotherapy is limited. Artemisinin and its analogs, such as dihydroartemisinin (DHA), can kill cancer cells via generating free radicals. In the present study, we determined whether DHA at low concentrations potentiates the cytotoxic effect of temozolomide in rat glioma C6 cells. We found that the IC₅₀ values of DHA and temozolomide for cell viability were 23.4 and 560 µmol/l, respectively. The cytotoxic effect of temozolomide was enhanced by 177% at a nontoxic DHA concentration (1 µmol/l), and by 321% at a low-toxic DHA concentration (5 µmol/l). DHA substantially increased temozolomide-induced apoptosis and necrosis. The generation of intracellular reactive oxygen species (ROS) was increased by temozolomide combined with DHA at noneffective concentrations of both agents. Edaravone (20 µmol/l), a ROS scavenger, reversed the effects of temozolomide/DHA on both ROS generation and cell viability reduction. These results indicate that DHA at low concentrations potentiates the cytotoxic effects of temozolomide in C6 cells partly via generating ROS, suggesting a beneficial combination for the chemotherapy of gliomas.

Biological activity of dihydroartemisinin in canine osteosarcoma cell lines

To evaluate the biological activity of dihydroartemisinin on canine osteosarcoma cell lines in vitro. 4 canine osteosarcoma cell lines. Cell viability assays were performed on canine osteosarcoma cell lines OSCA2, OSCA16, OSCA50, and D17 after 24, 48, and 72 hours of treatment with dihydroartemisinin at concentrations of 0.1 to 100 microM. Apoptosis was assessed by use of an ELISA for free nuclosomal DNA fragmentation and by western blot analysis for cleavage of caspase 3. Cell cycle analysis was performed by use of staining with propidium iodide and flow cytometry. Detection of reactive oxygen species (ROS) was conducted in the D17 cell line by use of 6-carboxy-2',7'-dihydrofluorescein diacetate and flow cytometry. The concentration of dihydroartemisinin required for 50% inhibition of cell viability (IC50) was achieved in all 4 canine osteosarcoma cell lines and ranged from 8.7 to 43.6 microM. Induction of apoptosis was evident as an increase in nucleosomal DNA fragmentation, cleavage of caspase 3, and an increase in the population in the sub G0/G1 phase of the cell cycle detected by flow cytometry. Exposure to dihydroartemisinin also resulted in a decrease in the G0/G1 population. Iron-dependent generation of ROS was detected in dihydroartemisinin-treated D17 cells; ROS generation increased in a dose-dependent manner. Incubation with dihydroartemisinin resulted in biological activity against canine osteosarcoma cell lines, which included induction of apoptosis and arrest of the cell cycle. Clinical trials of dihydroartemisinin in dogs with osteosarcoma should be conducted.

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.

Pharmacokinetics of dihydroartemisinin following oral artesunate treatment of pregnant women with acute uncomplicated falciparum malaria

To determine the pharmacokinetic properties of dihydroartemisinin (DHA) following oral artesunate treatment in women with recrudescent multi-drug resistant falciparum malaria, in the second and third trimesters of pregnancy. Serial plasma concentrations of artesunate and DHA were measured in 24 women after the final dose of a 3 day treatment with artesunate (4 mg kg(-1) day(-1)) and atovaquone (20 mg kg(-1) day(-1)) plus proguanil (8 mg kg(-1) day(-1)), daily. Conventional non-compartmental modelling and a population one-compartment pharmacokinetic model were applied to the data. Artesunate was very rapidly eliminated. For DHA the median [90% range] estimate of oral clearance (CI/F) was 4.0 [0.8-20.7] l hour(-1) kg(-1), total apparent volume of distribution (Vd/f) was 3.4 [0.9-60.7] l/kg, and terminal elimination half-life was 1.0 [0.6-2.4] h. The kinetics of DHA are modified by pregnancy. The plasma levels of the active antimalarial metabolite DHA are lower than reported previously in non-pregnant adults. Dose-optimisation studies in pregnant women are needed.

Dihydroartemisinin enhances radiosensitivity of human glioma cells in vitro

The antimalarial agent, artemisinin, also confers cancer-specific cytotoxic effects by reacting with ferrous iron atoms to form free radicals. Here, we investigated the radiosensitizing effects of dihydroartemisinin on glioma cells and assessed some possible mechanisms for these effects. U373MG glioma cells treated with various concentrations of dihydroartemisinin plus radiation, and efficiency of radiosensitization was assessed by clonogenic survival assay. Expression and activity of antioxidant enzymes, glutathione-S-transferase (GST) were quantified by western blot and enzymatic activity analyses, respectively. Dihydroartemisinin showed higher cytotoxicity in the glioma cell lines than in the liver, breast or cervical cancer cell lines. In clonogenic survival assays, treatment with dihydroartemisinin alone dose-dependently reduced the number of U373MG colonies, while treatment with dihydroartemisinin plus gamma-irradiation showed far lower clonal survival than cultures treated with radiation or dihydroartemisinin alone. The radiosensitizing effect of dihydroartemisinin was blocked significantly by the free radical scavengers, NAC and TIRON, indicating association with dihydroartemisinin-induced ROS generation. In addition, the radiation-induced expression of endogenous GST was suppressed by treatment with dihydroartemisinin. The radiosensitizing effect of dihydroartemisinin was also markedly enhanced by the addition of holotransferrin Taken together, our results strongly suggest that dihydroartemisinin triggers production of ROS and inhibits GST activity, leading to effective and therapeutically relevant radiosensitization of human glioma cells.