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The drugs available for Chagas disease treatment are toxic and ineffective. We studied the in vivo activity of a new drug, lychnopholide (LYC). LYC was loaded in nanocapsules (NC), and its effects were compared to free LYC and benznidazole against Trypanosoma cruzi. Infected mice were treated in the acute phase at 2.0 mg/kg/day with free LYC, LYC-poly-ε-caprolactone NC (LYC-PCL), and LYC-poly(lactic acid)-co-polyethylene glycol NC (LYC-PLA-PEG) or at 50 mg/kg/day with benznidazole solution by the intravenous route. Animals infected with the CL strain, treated 24 h after infection for 10 days, evaluated by hemoculture, PCR, and enzyme-linked immunosorbent assay exhibited a 50% parasitological cure when treated with LYC-PCL NC and 100% cure when treated with benznidazole, but 100% of the animals treated during the prepatent period for 20 days with these formulations or LYC-PLA-PEG NC were cured. In animals with the Y strain treated 24 h after infection for 10 days, only mice treated by LYC-PCL NC were cured, but animals treated in the prepatent period for 20 days exhibited 100, 75, and 62.5% cure when treated with LYC-PLA-PEG NC, benznidazole, and LYC-PCL NC, respectively. Free LYC reduced the parasitemia and improved mice survival, but no mice were cured. LYC-loaded NC showed higher cure rates, reduced parasitemia, and increased survival when used in doses 2five times lower than those used for benznidazole. This study confirms that LYC is a potential new treatment for Chagas disease. Furthermore, the long-circulating property of PLA-PEG NC and its ability to improve LYC efficacy showed that this formulation is more effective in reaching the parasite in vivo.

Doxycycline is reported to impair second-generation parasite schizogony. The effects of doxycycline alone and combined with dihydroartemisinin were investigated in a murine malaria model. Doxycycline lowered the rate of parasite growth within 2 days, with maximum effect in 6 days. Addition of dihydroartemisinin led to an additive antimalarial effect.

Dihydroartemisinin-piperaquine (DHP) is an important new treatment for drug-resistant malaria, although pharmacokinetic studies on the combination are limited. In Papua, Indonesia, we assessed determinants of the therapeutic efficacy of DHP for uncomplicated malaria. Plasma piperaquine concentrations were measured on day 7 and day 28, and the cumulative risk of parasitological failure at day 42 was calculated using survival analysis. Of the 598 patients in the evaluable population 342 had infections with Plasmodium falciparum, 83 with Plasmodium vivax, and 173 with a mixture of both species. The unadjusted cumulative risks of recurrence were 7.0% (95% confidence interval [CI]: 4.6 to 9.4%) for P. falciparum and 8.9% (95% CI: 6.0 to 12%) for P. vivax. After correcting for reinfections the risk of recrudescence with P. falciparum was 1.1% (95% CI: 0.1 to 2.1%). The major determinant of parasitological failure was the plasma piperaquine concentration. A concentration below 30 ng/ml on day 7 was observed in 38% (21/56) of children less than 15 years old and 22% (31/140) of adults (P = 0.04), even though the overall dose (mg per kg of body weight) in children was 9% higher than that in adults (P < 0.001). Patients with piperaquine levels below 30 ng/ml were more likely to have a recurrence with P. falciparum (hazard ratio [HR] = 6.6 [95% CI: 1.9 to 23]; P = 0.003) or P. vivax (HR = 9.0 [95% CI: 2.3 to 35]; P = 0.001). The plasma concentration of piperaquine on day 7 was the major determinant of the therapeutic response to DHP. Lower plasma piperaquine concentrations and higher failure rates in children suggest that dose revision may be warranted in this age group.

The effect of mefloquine on artesunate pharmacokinetics was assessed in 20 volunteers given artesunate for 3 days, followed > or =21 days later by combination therapy for 3 days. The areas under the concentration-time curve from 0 h to infinity for dihydroartemisinin, the active metabolite of artesunate, were similar on day 3 of the two dosing periods (P = 0.12), implying no interaction.

Drug treatment of severe malaria must be rapidly effective. Suppositories may be valuable for childhood malaria when circumstances prevent oral or parenteral therapy. We compared artesunate suppositories (n = 41; 8 to 16 mg/kg of body weight at 0 and 12 h and then daily) with intramuscular (i.m.) artemether (n = 38; 3.2 mg/kg at 0 h and then 1.6 mg/kg daily) in an open-label, randomized trial with children with severe Plasmodium falciparum malaria in Papua New Guinea (PNG). Parasite density and temperature were measured every 6 h for > or = 72 h. Primary endpoints included times to 50% and 90% parasite clearance (PCT50 and PCT90) and the time to per os status. In a subset of 29 patients, plasma levels of artemether, artesunate, and their common active metabolite dihydroartemisinin were measured during the first 12 h. One suppository-treated patient with multiple complications died within 2 h of admission, but the remaining 78 recovered uneventfully. Compared to the artemether-treated children, those receiving artesunate suppositories had a significantly earlier mean PCT50 (9.1 versus 13.8 h; P = 0.008) and PCT90 (15.6 versus 20.4 h; P = 0.011). Mean time to per os status was similar for each group. Plasma concentrations of primary drug plus active metabolite were significantly higher in the artesunate suppository group at 2 h postdose. The earlier initial fall in parasitemia with artesunate is clinically advantageous and mirrors higher initial plasma concentrations of active drug/metabolite. In severely ill children with malaria in PNG, artesunate suppositories were at least as effective as i.m. artemether and may, therefore, be useful in settings where parenteral therapy cannot be given.

The first-dose pharmacokinetic properties of intramuscular (i.m.) artesunate (ARTS; 2.4 mg/kg immediately [stat], followed by 1.2 mg/kg i.m. daily) and artemether (ARM; 3.2 mg/kg i.m. stat, followed by 1.6 mg/kg i.m. daily) were compared in Vietnamese adults with severe falciparum malaria. A total of 19 patients were studied; 9 received ARTS, and 10 received ARM. ARTS was absorbed very rapidly; concentrations in plasma peaked between 1,362 and 8,388 nmol/liter (median, 5,710 nmol/liter) within 20 min of injection and then declined with a median (range) half-life (t(1/2)) of 30 (3 to 67) min. ARTS was hydrolyzed rapidly and completely to the biologically active metabolite dihydroartemisinin (DHA). Peak DHA concentrations in plasma ranged between 1,718 and 7,080 nmol/liter (median, 3,060 nmol/liter) and declined with a t(1/2) of 52 (26 to 69) min. In contrast, ARM was slowly and erratically absorbed. The absorption profile appeared biphasic. Maximum ARM concentrations in plasma ranged between 67 nmol/liter (a value close to the 50% inhibitory concentration for some Plasmodium falciparum isolates) and 1,631 nmol/liter (median, 574 nmol/liter) and occurred at a median (range) of 10 (1.5 to 24) h. There was relatively little conversion to DHA. After i.m. injection in cases of severe malaria, absorption of the water-soluble ARTS is rapid and extensive, whereas the oil-based ARM is slowly and erratically absorbed, with relatively little conversion to the more active DHA. On the basis of this pharmacological study, parenteral ARTS is preferable to ARM as an initial antimalarial therapy, particularly in the most seriously ill patients. These findings should be formally assessed by a randomized clinical trial.

A detailed pharmacokinetic analysis was performed with 47 children from Papua New Guinea with uncomplicated falciparum or vivax malaria treated with artesunate (ARTS) suppositories (Rectocaps) given in two doses of approximately 13 mg/kg of body weight 12 h apart. Following an intensive sampling protocol, samples were assayed for ARTS and its primary active metabolite, dihydroartemisinin (DHA), by liquid chromatography-mass spectrometry. A population pharmacokinetic model was developed to describe the data. Following administration of the first dose, the mean maximal concentrations of ARTS and DHA were 1,085 nmol/liter at 0.9 h and 2,525 nmol/liter at 2.3 h, respectively. The absorption half-life for ARTS was 2.3 h, and the conversion half-life (ARTS to DHA) was 0.27 h, while the elimination half-life of DHA was 0.71 h. The mean common volumes of distribution for ARTS and DHA relative to bioavailability were 42.8 and 2.04 liters/kg, respectively, and the mean clearance values relative to bioavailability were 6 and 2.2 liters/h/kg for ARTS and DHA, respectively. Substantial interpatient variability was observed, and the bioavailability of the second dose relative to that of the first was estimated to be 0.72. The covariates age, sex, and alpha-thalassemia genotype were not influential in the pharmacokinetic model development; but the inclusion of weight as a covariate significantly improved the performance of the model. An ARTS suppositories dose of 10 of 20 mg/kg is appropriate for use in children with uncomplicated malaria.

The antimalarial activity of artemether following oral or intramuscular administration in the plasma of 15 adults with acute uncomplicated Plasmodium falciparum malaria was measured by bioassay. The peak concentrations in plasma following oral administration were higher in patients with acute illness (median, 1,905 mmol of dihydroartemisinin [DHA] equivalents per liter; range, 955 to 3,358 mmol of DHA equivalents per liter) than in patients in the convalescent phase (median, 955 mmol of DHA equivalents per liter; range, 576 to 1,363 mmol of DHA equivalents per liter), and clearance (CL/F) was lower in patients in the acute phase (1.11 liters/kg/h; range, 0.21 to 3.08 liters/kg/h) than in patients in the convalescent phase (median, 2.76 liters/kg/h; range, 1.56 to 5.74 liters/kg/h) (P< or =0.008). Antimalarial activity in terms of the peak concentration in plasma (Cmax) after oral administration was a median of 16 times higher than that after intramuscular administration. The ratio of the area under the plasma concentration-time curve during the first 24 h (AUC(0-24)) after oral administration of artemether to the AUC(0-24) after intramuscular administration was a median of 3.3 (range, 1 to 11) (P=0.0001). In the acute phase, the time to Cmax was significantly shorter after oral administration (median, 1 h; range, 0.5 to 3.0 h) than after intramuscular administration (median, 8 h; range, 4 to 24 h) (P=0.001). Intramuscular artemether is absorbed very slowly in patients with acute malaria.

Penetration of cerebrospinal fluid (CSF) by artesunate and DHA was assessed in six adults with cerebral or severe malaria. Lumbar punctures were performed on admission and during convalescence, at 15 min (patient 1), 30 min (patient 2), 45 min (patient 3), 60 min (patient 4), 90 min (patient 5), and 120 min (patient 6) after intravenous administration of 120 mg of artesunate. No artesunate was detectable in CSF. In both studies, DHA levels in CSF increased with time while dihydroartemisinin levels in plasma fell. Dihydroartemisinin might accumulate in CSF during frequent artesunate dosing.

Artesunate (ARS) is a water-soluble artemisinin derivative that is a potential alternative to quinine for the treatment of severe childhood malaria. We studied the pharmacokinetics and bioavailability of ARS given by the intramuscular (i.m.) route in an open crossover study design. Fourteen children were randomized to receive intravenous (i.v.) ARS in a loading dose (2.4 mg/kg of body weight) followed 12 h later by an i.m. dose (1.2 mg/kg) (group I), and 14 children were randomized to receive i.m. ARS (2.4 mg/kg) followed by an i.v. dose of ARS (1.2 mg/kg) (group II). We carried out a two-compartment analysis of ARS and dihydroartemisinin (DHA; the principal antimalarial metabolite) levels in 21 children (groups I and II combined). Absorption of i.m. ARS was rapid, with the maximum concentration of DHA in serum being achieved in less than 1 h in most children (median time to the maximum concentration of drug in serum, 35.1 min; range, 10.8 to 71.9 min). The absolute bioavailability of DHA was a median of 86.4% (range, 11.4 to 462.1%), the median steady-state volume of distribution was 1.3 liters/kg (range, 0.5 to 7.9 liters/kg), and the median clearance was 0.028 liters/kg/min (range, 0.001 to 1.58 liters/kg/min). There were no major adverse events attributable to ARS. Parasite clearance kinetics were comparable between the two treatment groups. These results support the use of i.m. ARS in children with severe malaria.

Plasma antimalarial activity following oral artesunate or dihydroartemisinin (DHA) treatment was measured by a bioassay in 18 patients with uncomplicated falciparum malaria. The mean antimalarial activity in terms of the bioavailability of DHA relative to that of artesunate did not differ significantly from 1, suggesting that DHA can be formulated to be an acceptable oral alternative to artesunate.

The immediate efficacies of two oral dosage regimens of artemisinin were investigated in 77 male and female adult Vietnamese falciparum malaria patients randomly assigned to treatment with either 500 mg of artemisinin daily for 5 days (group A; n = 40) or artemisinin at a dose of 100 mg per day for 2 days, with the dose increased to 250 mg per day for 2 consecutive days and with a final dose of 500 mg on the fifth day (group B; n = 37). Parasitemia was monitored every 4 h. The average parasite clearance time was longer in group B than in group A (means +/- standard deviations, 50 +/- 23 and 34 +/- 14 h, respectively; P < 0.01). Artemisinin concentrations in saliva samples obtained on days 1 and 5 were quantified by high-performance liquid chromatography. The average oral clearance, based on saliva drug concentrations in group B patients, was twofold higher than that in group A patients on day 1 (P < 0.01), with no differences in drug half-lives (P = 0.40), indicating a saturable first-pass metabolism. Female patients had higher oral clearance values on day 1. Artemisinin's pharmacokinetic parameters were similar on day 5 in both groups, although a significant increase in oral clearance from day 1 to day 5 was evident. Thus, artemisinin exhibited both dose- and time-dependent pharmacokinetics. The escalating dose studied did not result in higher artemisinin concentrations toward the end of the treatment period.

We report the first detailed pharmacokinetic assessment of intrarectal (i.r.) artesunate (ARS) in African children. Artesunate was given intravenously (i.v.; 2.4 mg/kg of body weight) and i.r. (10 or 20 mg/kg formulated as 50- or 200-mg suppositories [Rectocaps]) in a crossover study design to 34 Ghanaian children with moderate falciparum malaria. The median relative bioavailability of dihydroartemisinin (DHA), the active antimalarial metabolite of ARS, was higher in the low-dose i.r. group (10 mg/kg) than in the high-dose i.r. group (20 mg/kg) (58 versus 23%; P = 0.018). There was wide interpatient variation in the area under the concentration-time curve after i.r. ARS administration (up to 9-fold in the high-dose group and 20-fold in the low-dose group). i.r. administered ARS was more rapidly absorbed in the low-dose group than the high-dose group (median [range] absorption half-lives, 0.7 h [0.3 to 1.24 h] versus 1.1 h [0.6 to 2.7 h] [P = 0.023]. i.r. administered ARS was eliminated with a median (range) half-life of 0.8 h (0.4 to 2.7 h) (low-dose group and 0.9 h (0.1 to 2.5 h) (high-dose group) (P = 1). The fractional clearances of DHA were 3.9, 2.6, and 1.5 liters/kg/h for the 20-mg/kg, 10-mg/kg and i.v. groups, respectively (P = 0.001 and P = 0.06 for the high-and low-dose i.r. groups compared with the i.v. groups, respectively). The median volumes of distribution for DHA were 1.5 liters kg (20 mg/kg, i.r. group), 1.8 liters/kg (10 mg/kg, i.r. group), and 0.6 liters/kg (i.v. group) (P < 0.05 for both i.r. groups compared with the i.v. group). Parasite clearance kinetics were comparable in all treatment groups. i.r. administered ARS may be a useful alternative to parenterally administered ARS in the management of moderate childhood malaria and should be studied further.

To provide novel data relating to the dispositions, effects, and toxicities of the artemisinin derivatives in severe malaria, we studied 30 Vietnamese adults with slide-positive falciparum malaria treated with intravenous artesunate. Twelve patients with complications (severe; group 1) and 8 patients without complications but requiring parenteral therapy (moderately severe; group 2) received 120 mg of artesunate by injection, and 10 patients with moderately severe complications (group 3) were given 240 mg by infusion. Serial concentrations of artesunate and its active metabolite dihydroartemisinin in plasma were measured by high-performance liquid chromatography. The time to 50% parasite clearance (PCT(50)) was determined from serial parasite densities. Full clinical (including neurological) assessments were performed at least daily. In noncompartmental pharmacokinetic analyses, group mean artesunate half-lives (t(1/2)) were short (range, 2.3 to 4.3 min). The dihydroartemisinin t(1/2) (range, 40 to 64 min), clearance (range, 0.73 to 1.01 liters/h/kg), and volume of distribution (range, 0.77 to 1.01 liters/kg) were also similar both across the three patient groups (P > 0.1) and to previously reported values for patients with uncomplicated malaria. Parasite clearance was prompt (group median PCT(50) range 6 to 9 h) and clinical recovery was complete under all three regimens. These data indicate that the pharmacokinetics of artesunate and dihydroartemisinin are not influenced by the severity of malaria. Since the pharmacokinetic parameters for both artesunate and dihydroartemisinin were similar regardless of whether injection or infusion was used, artesunate can be considered a prodrug that is converted stoichiometrically to dhydroartemisinin. Conventional doses of artesunate are safe and effective when given to patients with complications of falciparum malaria.

Combinations of artemisinin and quinine for uncomplicated falciparum malaria were studied. A total of 268 patients were randomized to 7 days of quinine at 10 mg/kg of body weight three times a day (Q) or to artemisinin at 20 mg/kg of body weight followed by 3 (AQ3) or 5 (AQ5) days of quinine. Recrudescence rates were 16, 38, and 15% for the Q, AQ3, and AQ5 groups, respectively (P < 0.001). Recrudescence was associated with shorter parasite clearance time (PCT) and longer treatment after the blood smear had become negative (eradication time). However, classification of patients to outcome-recrudescence or radical cure-was correct in only 77% of patients. The population kinetics of the parasitemia was estimated with nonlinear mixed-effect models. Several models were tested, but the best model was a monoexponential decline of the parasitemia in which the mean parasite elimination half-life was shorter after artemisinin (5.1 h; 95% confidence interval [CI], 4.9 to 5.2 h) than after quinine (8.0 h [95% CI, 7.5 to 8.3 h]). Attempts to simulate the initial increase of the parasitemia did not result in better models with a biologically plausible interpretation. Recrudescence was associated with slower parasite clearance and a higher simulated terminal parasitemia (P(term)). The classification of patients to outcome groups based on P(term) was correct in 78% of patients. The data suggest that parasite strains with reduced sensitivity to quinine are prevalent in Vietnam, with slower parasite clearance and consequent recrudescence. A single dose of artemisinin induces rapid parasite reduction and lowers the value of P(term), but to prevent recrudescence, this should be followed by quinine for at least 3 days after parasite clearance, or 5 days in total.

The pharmacokinetic properties of oral and intravenous artesunate (2 mg/kg of body weight) were studied in 19 adult patients with acute uncomplicated Plasmodium falciparum malaria by using a randomized crossover design. A sensitive bioassay was used to measure the antimalarial activity in plasma which results from artesunate and its principal metabolite, dihydroartemisinin. The oral study was repeated with 15 patients during convalescence. The mean absolute oral bioavailability of the antimalarial agent in patients with acute malaria was 61% (95% confidence interval [CI], 52 to 70%). The absorption and elimination of oral artesunate were rapid, with a mean elimination half-life of antimalarial activity of 43 min (95% CI, 33 to 53 min). Following oral administration to patients with acute falciparum malaria, peak antimalarial activity in plasma and the area under the plasma concentration-time curve were approximately double those during convalescence and the apparent volume of distribution and clearance were approximately half those during convalescence (P < or = 0.005). Acute malaria is associated with a significant reduction in the clearance of artesunate-associated antimalarial activity.

Six patients with uncomplicated falciparum malaria received artesunate for 5 days. Plasma concentrations of artesunate and dihydroartemisinin were determined by high-performance liquid chromatography with electrochemical detection. The concentrations of dihydroartemisinin in plasma 2 h after a dose showed a time-dependent decline. Concentrations of artesunate in plasma especially after the last dose, were very low. Despite this, all patients responded with a fast recovery.

Combining artemisinin or a derivative with mefloquine increases cure rates in falciparum malaria patients, reduces transmission, and may slow the development of resistance. The combination of artesunate, given for 3 days, and mefloquine is now the treatment of choice for uncomplicated multidrug-resistant falciparum malaria acquired on the western or eastern borders of Thailand. To optimize mefloquine administration in this combination, a prospective study of mefloquine pharmacokinetics was conducted with 120 children (4 to 15 years old) with acute uncomplicated falciparum malaria, who were divided into four age- and sex-matched groups. The patients all received artesunate (4 mg/kg of body weight/day orally for 3 days and mefloquine as either (i) a single dose (25 mg/kg) on day 2 with food, (ii) a split dose (15 mg/kg on day 2 and 10 mg/kg on day 3) with food, (iii) a single dose (25 mg/kg) on day 0 without food, or (iv) a single dose (25 mg/kg) on day 2 without food. Delaying administration of mefloquine until day 2 was associated with a mean (95% confidence interval) increase in estimated oral bioavailability of 72% (36 to 109%). On day 2 coadministration with food did not increase mefloquine absorption significantly, and there were no significant differences between patients receiving split- and single-dose administration. In combination with artesunate, mefloquine administration should be delayed until the second or third day after presentation.

Thalassemia is common in Southeast Asia, where artemisinin derivatives are frequently used in the treatment of malaria. It has been previously reported that artemisinin derivatives can be concentrated by uninfected thalassemic erythrocytes in vitro but not by normal erythrocytes. As a follow-up to this report, we studied the antimalarial kinetics of intravascular artesunate (2.4 mg/kg of body weight) in 10 persons with normal hemoglobins and in 10 patients with thalassemia (2 with alpha-thalassemia type 1-hemoglobin Constant Spring and 8 with alpha-thalassemia type 1-alpha-thalassemia type 2). Concentrations of artesunate and its active metabolites in plasma were measured by bioassay and expressed relative to those of dihydroartemisinin, the major biologically active metabolite. Concentrations of intravascular artesunate in plasma peaked in both the normal individuals and the thalassemic individuals 15 min after injection (the first time point). Plasma drug concentrations at all time intervals, except that at 1 h, were significantly higher in thalassemic subjects than in normal subjects (P < 0.05). The area under the concentration-time curve was 9-fold higher (P < 0.001) and the volume of distribution at steady state was 15-fold lower (P < 0.001) in thalassemic than in normal subjects. In light of the potential neurotoxicity of artemisinin derivatives, these results suggest that thalassemic subjects may need a drug administration regimen different from that of normal patients.

The influence of food intake on the pharmacokinetics of artemisinin was studied with six healthy Vietnamese male subjects. In a crossover study, artemisinin capsules (500 mg) were administered with and without food after an overnight fast. Plasma samples were obtained up to 24 h after intake of each drug. Measurement of artemisinin concentrations was performed by high-performance liquid chromatography with electrochemical detection. Tolerance was evaluated according to subjective and objective findings, including repeated physical examinations, routine blood investigations, and electrocardiograms. Pharmacokinetics were analyzed with a noncompartmental method and with a one-compartment model. This model had either zero-order or first-order input. No statistically significant differences were found between the results of the two experimental conditions. Specifically, there were no consistent differences in parameters most likely to be affected by food intake, including absorption profile, absorption rate, bioavailability (f) (as reflected in area under the concentration time curve [AUC]), and drug clearance. Some mean +/- standard deviation parameters after food were as follows: maximum concentration of drug in serum (Cmax), 443 +/- 224 microg x liter(-1); time to Cmax, 1.78 +/- 1.2 h; AUC, 2,092 +/- 1,441 ng x ml(-1) x h, apparent clearance/f, 321 +/- 167 liter x h(-1); mean residence time, 4.42 +/- 1.31 h; and time at which half of the terminal value was reached, 0.97 +/- 0.68 h. The total amount of artemisinin excreted in urine was less than 1% of the dose. We conclude that food intake has no major effect on artemisinin pharmacokinetics. In addition, we conclude tentatively that artemisinin is cleared by the liver, that this clearance does not depend on liver blood flow (i.e., that artemisinin is a so-called low-clearance drug), and that absorption of the drug is not affected by food intake.