Population Pharmacokinetics of Pyrimethamine and Sulfadoxine in Children Treated for Congenital Toxoplasmosis

ABSTRACT The population pharmacokinetics of pyrimethamine (PYR) and sulfadoxine (SDX) for a group of 32 children with congenital toxoplasmosis was investigated by nonparametric modeling analysis. A one-compartment model was used as the structural model, and individual pharmacokinetic parameters were estimated by Bayesian modeling. PYR (1.25 mg/kg of body weight) and SDX (25 mg/kg) were administered orally every 10 days for 1 year, with adjustment of the dose to body weight every 3 months. Drug concentrations were measured by high-performance liquid chromatography. A total of 101 measurements in serum were available for both drugs. Mean absorption rate constants, volumes of distribution, elimination rate constants, and half-lives were 0.915 h−1, 4.379 liters/kg, 0.00839 h−1, and 5.5 days for PYR and 1.659 h−1, 0.392 liters/kg, 0.00526 h−1, and 6.6 days for SDX, respectively. Wide interindividual variability was observed. The estimated minimum and maximum concentrations of PYR in serum differed 8- and 25-fold among patients, respectively, and those of SDX differed 4- and 5-fold, respectively. Increases in the concentration of PYR were observed for eight children, and increases in the SDX concentration were observed for seven children. Serum PYR-SDX concentrations are unpredictable even when the dose is standardized for body weight. The concentrations of the PYR-SDX combination that are most efficacious for children have not yet been established. A model such as ours, associated with long-term follow-up, is needed to study the correlation between exposure to these two drugs and clinical outcome in children.

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Population Pharmacokinetics of Piritramide in Surgical Patients

Anesthesiology ◽

10.1097/00000542-199901000-00004 ◽

1999 ◽

Vol 90 (1) ◽

pp. 7-15 ◽

Cited By ~ 30

Author(s):

Thomas Bouillon ◽

Daniela Kietzmann ◽

Rudiger Port ◽

Ingolf Meineke ◽

Andreas Hoeft

Keyword(s):

Population Pharmacokinetics ◽

Venous Blood ◽

Compartment Model ◽

Mixed Effects ◽

Pharmacokinetic Parameters ◽

Effect Compartment ◽

Bolus Administration ◽

Time Data ◽

Intermittent Bolus ◽

Patient Consent

Background Piritramide is a synthetic opioid used for postoperative analgesia in several European countries. The authors present a mixed-effects model of its population pharmacokinetics in patients undergoing surgery. Methods After institutional approval and informed patient consent was obtained, 29 patients who were classified as American Society of Anesthesiologists physical status I or II and aged 21-82 yr were enrolled in the study. They received 0.2 mg/kg piritramide as an intravenous bolus before anesthesia was induced. Central venous blood samples were drawn for as long as 48 h after administration of the drug. The plasma concentration of piritramide was determined by gas chromatography. The concentration-time data were analyzed by mixed-effects modeling. Target-controlled infusions and intermittent bolus regimens were simulated to identify a regimen suitable for patient-controlled analgesia based on population pharmacokinetics and published pharmacodynamic data. Results The pharmacokinetics of piritramide were described adequately by a linear three-compartment model. Patient age and weight were significant covariates. The values of the pharmacokinetic parameters are: V1 = 50.5 [1], V2 = 150 x (1 + 9.32 x 10(-3) x (age - 47 yr)) [l], V3 = 212 x (1 + 6.37 x 10(-3) x (age - 47 yr)) [l], Cl1 = 0.56 x (1 - 6.14 x 10(-3) x (age - 47 yr)) [l/min], Cl2 = 8.25 x (1 + 2.02 x 10(-2) x (Wt - 74 kg)) [l/min], Cl3 = 0.80 [l/min]. The age of 47 yr and the weight of 74 kg refer to the median values for these factors in the patients studied. Rapid distribution, slow distribution, and elimination half-lives for the median patient are 0.05, 1.34, and 10.43 h, respectively. The context-sensitive half-time after a 24-h infusion is predicted at 10.5 h in a 75-yr-old patient compared with 7 h for the median patient. Conclusions Piritramide is distributed extensively and eliminated slowly. The pharmacokinetic profile of the drug allows for intermittent bolus administration even when constant effect compartment concentrations are desirable, e.g., for PLA.

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Withdrawal of cefoperazone with milk after intramammary administration in dairy cows – prospective and retrospective analysis

Polish Journal of Veterinary Sciences ◽

10.1515/pjvs-2017-0031 ◽

2017 ◽

Vol 20 (2) ◽

pp. 261-268

Author(s):

A. Burmańczuk ◽

T. Grabowski ◽

T. Błądek ◽

C. Kowalski ◽

P. Dębiak

Keyword(s):

Dairy Cows ◽

Half Life ◽

Drug Distribution ◽

Compartment Model ◽

Clinical Mastitis ◽

Pharmacokinetic Analysis ◽

Pharmacokinetic Parameters ◽

Lactation Period ◽

Milk Samples ◽

Drug Concentrations

Abstract The aim of the study was to carry out retrospective and prospective comparative analyses of the pharmacokinetics of CEF after single intramammary (IMM) administration in cows. The prospective study (study A) was conducted on 9 dairy cows of the Polish Black-White race with clinical mastitis during the lactation period. Milk samples were collected at 2, 4, 6, 8, 10, 24, 36, 48, 72 and 84 h after single IMM administration of 250 mg of CEF to one quarter. Drug concentrations in milk samples were determined by HPLC-MS/MS technique and the results of the pharmacokinetic analysis were compared to those obtained in previous studies based on the microbiological (study B) and HPLC-UV methods (study C and D). Pharmacokinetic parameters were calculated based on adapted two-compartment model of drug distribution. One of the findings of the comparison of the analysed investigations is that the CEF kinetics determined with the microbiological method is consistent with the results obtained by the authors of this paper. Both studies yielded similar results of the key pharmacokinetic parameters related to the level of the drug distribution to tissues and elimination half-life. In the pharmacodynamic analysis, the observations in all four studies were entirely consistent and have shown lower values of T>MIC90 in healthy animals and significantly higher values in infected dairy cows. The comparison of studies A, B, C, and D revealed that the time of complete CEF wash-out of 90.90% varied and amounted to 5.7, 8.0, 2.2, and 2.2 days after administration of the drug, respectively. It was confirmed that not only the type of the analytical method but also correct sampling have a significant impact on determination of the correct value of the drug half-life after IMM administration. The comparative analysis of studies in which the milk yield was high and low allows a conclusion that this parameter in the case of CEF has no significant effect on T>MIC90.

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Pharmacokinetic aspects of Tert-Butylaminoethyl disulfide, an experimental drug against schistosomiasis in mice

Memórias do Instituto Oswaldo Cruz ◽

10.1590/s0074-02761989000100017 ◽

1989 ◽

Vol 84 (1) ◽

pp. 95-102 ◽

Cited By ~ 1

Author(s):

M. M. Guerra Andrade ◽

A. C. T. Freire ◽

D. L. Nelson

Keyword(s):

Elimination Rate ◽

Compartment Model ◽

Pharmacokinetic Parameters ◽

Model Combining ◽

Experimental Drug ◽

Drug Plasma ◽

Cationic Resin ◽

Dose Dependent ◽

Pass Metabolism ◽

Pharmacokinetic Behavior

A preliminary study of the pharmacokinetic parameters of t-Butylaminoethyl disulfide was performed after administration of two different single doses (35 and 300 mg/kg) of either the cold or labelled drug. Plasma or blood samples were treated with dithiothreitol, perchloric acid, and, after filtration, submitted to further purification with anionic resein. In the final step, the drug was retained on a cationic resin column, eluted with NaCl 1M and detected according to the method of Ellman (1958). Alternatively, radioactive drug was detected by liquid scintillation counting. The results corresponding to the smaller dose of total drug suggested a pharmacokinetic behavior related to a one open compartment model with the following parameters: area under the intravenous curve (AUC i.v.):671 ± 14; AUC oral: 150 ± 40 µg.min. ml [raised to the power of -1]; elimination rate constant: 0.071 min [raised to the power of -1]; biological half life: 9.8 min; distribution volume: 0.74 ml/g. For the higher dose, the results seemed to obey a more complex undertermined model. Combining the results, the occurence of a dose-dependent pharmacokinetic behavior is suggested, the drug being rapidly absorbed and rapidly eliminated; the elimination process being related mainly to metabolization. The drug seems to be more toxic when administered I.V. because by this route it escapes first pass metabolism, while being quickly distributed to tissues. The maximum tolerated blood level seems to be around 16 µg/ml.

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Zalcitabine Population Pharmacokinetics: Application of Radioimmunoassay

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.42.2.409 ◽

1998 ◽

Vol 42 (2) ◽

pp. 409-413 ◽

Cited By ~ 2

Author(s):

John M. Adams ◽

Mark J. Shelton ◽

Ross G. Hewitt ◽

Mary DeRemer ◽

Robin DiFrancesco ◽

...

Keyword(s):

Population Pharmacokinetics ◽

Information Age ◽

Compartment Model ◽

Volume Of Distribution ◽

Pharmacokinetic Parameters ◽

Pharmacokinetic Studies ◽

Oral Clearance ◽

Standard Curve ◽

Immunodeficiency Virus ◽

Traditional Approaches

ABSTRACT Zalcitabine population pharmacokinetics were evaluated in 44 human immunodeficiency virus-infected patients (39 males and 5 females) in our immunodeficiency clinic. Eighty-one blood samples were collected during routine clinic visits for the measurement of plasma zalcitabine concentrations by radioimmunoassay (1.84 ± 1.24 samples/patient; range, 1 to 6 samples/patient). These data, along with dosing information, age (38.6 ± 7.13 years), sex, weight (79.1 ± 15.0 kg), and estimated creatinine clearance (89.1 ± 21.5 ml/min), were entered into NONMEM to obtain population estimates for zalcitabine pharmacokinetic parameters (4). The standard curve of the radioimmunoassay ranged from 0.5 to 50.0 ng/ml. The observed concentrations of zalcitabine in plasma ranged from 2.01 to 8.57 ng/ml following the administration of doses of either 0.375 or 0.75 mg. A one-compartment model best fit the data. The addition of patient covariates did not improve the basic fit of the model to the data. Oral clearance was determined to be 14.8 liters/h (0.19 liter/h/kg; coefficient of variation [CV] = 23.8%), while the volume of distribution was estimated to be 87.6 liters (1.18 liters/kg; CV = 54.0%). We were also able to obtain individual estimates of oral clearance (range, 8.05 to 19.8 liters/h; 0.11 to 0.30 liter/h/kg) and volume of distribution (range, 49.2 to 161 liters; 0.43 to 1.92 liters/kg) of zalcitabine in these patients with the POSTHOC option in NONMEM. Our value for oral clearance agrees well with other estimates of oral clearance from traditional pharmacokinetic studies of zalcitabine and suggests that population methods may be a reasonable alternative to these traditional approaches for obtaining information on the disposition of zalcitabine.

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Population Pharmacokinetics of Nevirapine, Zidovudine, and Didanosine in Human Immunodeficiency Virus-Infected Patients

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.43.1.121 ◽

1999 ◽

Vol 43 (1) ◽

pp. 121-128 ◽

Cited By ~ 60

Author(s):

Xiao-Jian Zhou ◽

Lewis B. Sheiner ◽

Richard T. D’Aquila ◽

Michael D. Hughes ◽

Martin S. Hirsch ◽

...

Keyword(s):

Human Immunodeficiency Virus ◽

Body Weight ◽

Population Pharmacokinetics ◽

Compartment Model ◽

Volume Of Distribution ◽

Zero Order ◽

Triple Combination ◽

Entire Study ◽

First Order ◽

Immunodeficiency Virus

ABSTRACT The population pharmacokinetics of nevirapine (NVP), zidovudine (ZDV), and didanosine (ddI) were evaluated in a total of 175 patients infected with human immunodeficiency virus randomized to receive either a double combination of ZDV plus ddI or a triple combination of NVP plus ZDV plus ddI as a substudy of the AIDS Clinical Trials Group Protocol 241. Levels (approximating 3.5 determinations/patient) of the three drugs in plasma were measured during 44 of a total 48 weeks of study treatment, and a set of potential covariates was available for nonlinear mixed-effect modeling analysis. A one-compartment model with zero-order input and first-order elimination was fitted to the NVP data. Individual oral clearance (CL) and volume of distribution (V) averaged 0.0533 liters/h/kg of body weight and 1.17 liters/kg, respectively. Gender was the only covariate which significantly correlated with the CL of NVP. ZDV and ddI data were described by a two-compartment model with zero-order input and first-order elimination. Individual mean oral CL,V SS (volume of distribution at steady state), and V of ZDV were 1.84 liters/h/kg and 6.68 and 2.67 liters/kg, respectively, with body weight and age as correlates of CL and body weight as a correlate of V SS. The average individual oral CL, V SS, andV of ddI were 1.64 liters/h/kg and 3.56 and 2.74 liters/kg, respectively, with body weight as a significant correlate of both CL and V SS. The relative bioavailability (F) of ZDV and ddI in the triple combination compared to that in the double combination was also evaluated. No significant effects of the combination regimens on the F of ddI were detected (F TRIPLE = 1.05 andF DOUBLE = 1 by definition), but theF of ZDV was markedly reduced by the triple combination, being only 67.7% of that of the double combination. Large (>50%) intraindividual variability was associated with both ZDV and ddI pharmacokinetics. Individual cumulative area under the plasma drug level-time curve of the three drugs was calculated for the entire study period as a measure of drug exposure based on the individual data and the final-model estimates of structural and statistical parameters.

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Pharmacokinetics of Intermittent Intraperitoneal Cefazolin in Continuous Ambulatory Peritoneal Dialysis Patients

Peritoneal Dialysis International ◽

10.1177/089686089901900111 ◽

1999 ◽

Vol 19 (1) ◽

pp. 65-70 ◽

Cited By ~ 28

Author(s):

Harold J. Manley ◽

George R. Bailie ◽

Rupesh D. Asher ◽

George Eisele ◽

Reginald F. Frye

Keyword(s):

Body Weight ◽

Peritoneal Dialysis ◽

Continuous Ambulatory Peritoneal Dialysis ◽

Rate Constant ◽

Half Life ◽

Elimination Rate ◽

Pharmacokinetic Parameters ◽

Number Of Patients ◽

The Mean ◽

Concentration Levels

Objective To investigate the pharmacokinetic parameters of intermittent intraperitoneal (IP) cefazolin, and recommend a cefazolin dosing regimen in continuous ambulatory peritoneal dialysis (CAPD) patients. Design Prospective nonrandomized open study. Setting CAPD outpatient clinic in Albany, New York. Patients Seven volunteer CAPD patients without peritonitis. Three of the patients were nonanuric while 4 were anuric. Interventions Cefazolin (15 mg/kg total body weight) was given to each patient during the first peritoneal exchange. Blood and dialysate samples were collected at times 0, 0.5, 1, 2, 3, 6 (end of the first antibiotic-containing dwell), 24, and 48 hours after the administration of IP cefazolin. Urine samples were collected in nonanuric patients over the study period. Results The mean ± SD amount of cefazolin dose absorbed from the dialysate after the 6-hour dwell was 69.7% ± 8.0% of the administered dose. The cefazolin absorption rate constant from dialysate to serum was 0.21 ± 0.1 /hr (absorption half-life 3.5 ± 0.8 hr). The mean serum concentrations reached at 24 and 48 hours were 52.4 ± 3.7 mg/L and 30.3 ± 5.9 mg/L, respectively. The mean dialysate cefazolin concentrations reached at 24 and 48 hours were 15.1 ± 3.4 mg/L and 7.9 ± 1.4 mg/L, respectively. The cefazolin serum elimination rate constant was 0.02 ± 0.01 /hr (elimination half-life 31.5 ± 8.8 hr). The total cefazolin body clearance was 3.4 ± 0.6 mL/min. In the 3 nonanuric patients the mean renal clearance of cefazolin was 0.6 ± 0.4 mL/min. The peritoneal clearance of cefazolin was 1.0 ± 0.3 mL/min. The systemic volume of distribution of cefazolin was 0.2 ± 0.05 L/kg. No statistical difference was detected in pharmacokinetic parameters between anuric and nonanuric patients, although this may be due to the small number of patients in each group. Conclusion A single daily dose of cefazolin dosed at 15 mg/kg actual body weight in CAPD patients is effective in achieving serum concentration levels greater than the minimum inhibitory concentration for sensitive organisms over 48 hours, and dialysate concentration levels over 24 hours. Caution is warranted in extrapolation of dosing recommendations to patients who maintain a significant degree of residual renal function.

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Population Pharmacokinetics of Cyclophosphamide in Patients with Thalassaemia Major Undergoing HSCT Shows Body Weight, CYP450, GST and ALDH Polymorphisms as Covariates Explaining Inter-Individual Variation.

Blood ◽

10.1182/blood.v114.22.1182.1182 ◽

2009 ◽

Vol 114 (22) ◽

pp. 1182-1182 ◽

Cited By ~ 2

Author(s):

Poonkuzhali Balasubramanian ◽

John Carl Panetta ◽

Salamun Desire ◽

Shaji R Velayudhan ◽

Vikram Mathews ◽

...

Keyword(s):

Body Weight ◽

Individual Variation ◽

Conflicts Of Interest ◽

Conditioning Regimen ◽

Elimination Rate ◽

Pharmacokinetic Parameters ◽

Thalassaemia Major ◽

Hematopoietic Stem ◽

Beta Thalassaemia ◽

Population Pk

Abstract Abstract 1182 Poster Board I-204 Cyclophosphamide (Cy) in combination with busulfan is an important component of myeloablative conditioning regimen used prior to hematopoietic stem cell transplantation (HSCT) for both malignant and non-malignant conditions. We have previously reported up to 20 fold inter-individual variation in the pharmacokinetics (PK) of Cy in patients with beta thalassaemia undergoing HSCT [Blood (ASH Annual Meeting Abstracts), Nov 2004; 104: 99]. PK parameters of Cy have been shown to be associated with regimen related toxicity and outcome of transplant. To explain the basis of the inter-individual variation in Cy PK, we have developed a population PK model. We analyzed the PK of Cy in consecutive children with beta thalassaemia major who received HSCT from HLA identical matched sibling donor at the Christian Medical College, Vellore from 2001 till 2004. A total of 900 cyclophosphamide concentration measurements from 55 patients were included and correlated with age, sex, body weight and 10 polymorphisms in enzymes involved in the metabolism or biotransformation of Cy namely GST A1, M1, T1, P1, CYP2B6, CYP2C9, CYP2C19 and ALDH genes. Non-linear mixed effects modeling analysis was performed with Monolix (version 2.4, www.monolix.org) to investigate the effect of patient covariates on PK, and to estimate the relative magnitude of inter-individual and inter-occasion variability. A two-compartment pharmacokinetic model was used to describe the data. The pharmacokinetic parameters estimated included elimination rate constant and volume (ke (1/hr), V (L or L/kg)), and the inter-compartmental parameters (k12 and k21 (1/hr)). The distribution of the parameters was assumed log-normal. Body weight was the main covariate which explained the largest portion of the IIV (28% and 20% of V and ke IIV, respectively). In addition, the following genotypes showed differences in the pharmacokinetics: GSTP1*B (1.7X higher ke in MUT versus WT or HET; p<0.05), CYP3A4*1B (2X higher ke in HET versus WT; p<0.05), and ALDH1A1*2 (2X higher ke in HET versus WT; p<0.05). We have developed a population PK model for Cy in thalassaemic children by considering morphological and biological covariates, which explains more than 45% and 22% (V and ke IIV, respectively) of the variation in Cy PK in these patients. This model-based algorithm may be used to design and plan targeted dose therapy in this group of pediatric patients and to predict the risk of toxicity and outcome of HSCT. Disclosures: No relevant conflicts of interest to declare.

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Pharmacokinetics of Tranexamic Acid in Neonates, Infants, and Children Undergoing Cardiac Surgery with Cardiopulmonary Bypass

Anesthesiology ◽

10.1097/aln.0000000000000570 ◽

2015 ◽

Vol 122 (4) ◽

pp. 746-758 ◽

Cited By ~ 37

Author(s):

Mark C. Wesley ◽

Luis M. Pereira ◽

Laurie A. Scharp ◽

Sitaram M. Emani ◽

Francis X. McGowan ◽

...

Keyword(s):

Cardiopulmonary Bypass ◽

Young Children ◽

Tranexamic Acid ◽

High Performance ◽

Structural Model ◽

Heart Defects ◽

Circulatory Arrest ◽

Pharmacokinetic Analysis ◽

Pharmacokinetic Parameters ◽

First Time

Abstract Background: Tranexamic acid (TXA) is one of the most commonly used antifibrinolytic medications in children undergoing repair of congenital heart defects. However, a pharmacokinetics analysis of TXA has never been performed in neonates or young children undergoing complex cardiac surgeries using cardiopulmonary bypass, hypothermia, circulatory arrest, and ultrafiltration. A comprehensive pharmacokinetics study was performed in this patient population. Methods: Fifty-five patients ranging from 2 days through 4 yr old were categorized into three groups: children less than 2 months old, infants 2 months to 1 yr old, and children greater than 1 yr old and weighing up to 20 kg. TXA was given as a bolus of 100 mg/kg followed by an infusion of 10 mg · kg−1 · h−1 throughout the surgery. A dose of 100 mg/kg was placed in the cardiopulmonary bypass prime. A total of 16 to 18 samples were obtained from all patients throughout surgery. Plasma TXA concentrations were measured by high-performance liquid chromatography and modeled under a nonlinear mixed-effects framework with a two-compartment structural model. Results: Cardiopulmonary bypass had a statistically significant impact on all pharmacokinetic parameters. Age was a better covariate than body weight, affecting both the distribution and the elimination of TXA. However, weight performed well in some cases. Other covariates including body surface area, pump prime volume, ultrafiltrate volume, and body temperature did not improve the model. Conclusions: This TXA pharmacokinetic analysis is reported for the first time in neonates and young children undergoing complex cardiac surgeries with cardiopulmonary bypass. Dosing recommendations are provided as guidance for maintaining desired target concentrations.

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Joint Population Pharmacokinetic Analysis of Zidovudine, Lamivudine, and Their Active Intracellular Metabolites in HIV Patients

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01487-10 ◽

2011 ◽

Vol 55 (7) ◽

pp. 3423-3431 ◽

Cited By ~ 15

Author(s):

C. Bazzoli ◽

H. Bénech ◽

E. Rey ◽

S. Retout ◽

D. Salmon ◽

...

Keyword(s):

Compartment Model ◽

Population Pharmacokinetic Analysis ◽

Pharmacokinetic Analysis ◽

Pharmacokinetic Parameters ◽

Population Pharmacokinetic ◽

Intracellular Metabolites ◽

Drug Concentrations ◽

The Mean ◽

Intracellular Concentrations ◽

Apparent Bioavailability

ABSTRACTThe population pharmacokinetic parameters of zidovudine (AZT), lamivudine (3TC), and their active intracellular metabolites in 75 naïve HIV-infected patients receiving an oral combination of AZT and 3TC twice daily as part of their multitherapy treatment in the COPHAR2-ANRS 111 trial are described. Four blood samples per patient were taken after 2 weeks of treatment to measure drug concentrations at steady state. Plasma AZT and 3TC concentrations were measured in 73 patients, and among those, 62 patients had measurable intracellular AZT-TP and 3TC-TP concentrations. For each drug, a joint population pharmacokinetic model was developed and we investigated the influence of different covariates. We then studied correlations between the mean plasma and intracellular concentrations of each drug. A one-compartment model with first-order absorption and elimination best described the plasma AZT concentration, with an additional compartment for intracellular AZT-TP. A similar model but with zero-order absorption was found to adequately described concentrations of 3TC and its metabolite 3TC-TP. The half-lives of AZT and 3TC were 0.81 h (94.8%) and 2.97 h (39.2%), respectively, whereas the intracellular half-lives of AZT-TP and 3TC-TP were 10.73 h (69%) and 21.16 h (44%), respectively. We found particularly a gender effect on the apparent bioavailability of AZT, as well as on the mean plasma and intracellular concentrations of AZT, which were significantly higher in females than in males. Relationships between mean plasma drug and intracellular metabolite concentrations were also highlighted both for AZT and for 3TC. Simulation with the model of plasma and intracellular concentrations for once- versus twice-daily regimens suggested that a daily dosing regimen with double doses could be appropriate.

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Artemisinin Pharmacokinetics and Efficacy in Uncomplicated-Malaria Patients Treated with Two Different Dosage Regimens

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.46.4.1026-1031.2002 ◽

2002 ◽

Vol 46 (4) ◽

pp. 1026-1031 ◽

Cited By ~ 39

Author(s):

Toufigh Gordi ◽

Dinh Xuan Huong ◽

Trinh Ngoc Hai ◽

Nguyen Thi Nieu ◽

Michael Ashton

Keyword(s):

High Performance ◽

Parasite Clearance ◽

Oral Dosage ◽

Pharmacokinetic Parameters ◽

Oral Clearance ◽

Dosage Regimens ◽

Drug Concentrations ◽

Group A ◽

Group B ◽

Pass Metabolism

ABSTRACT 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.

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