Pharmacokinetics and pharmacodynamics of a new ACT formulation: Artesunate/Amodiaquine (TRIMALACT) following oral administration in African malaria patients.

A new fixed-dose combination of artesunate (AS) plus amodiaquine (AQ) (TRIMALACT) was recently developed for the treatment of uncomplicated falciparum malaria. The originality of this combination lies in its galenic formulation which consists of a three-layer tablet with two layers containing each of the active ingredients, i.e. AS and AQ, and these are separated by a middle layer containing an antioxidant compound. To evaluate the efficacy and tolerability of this combination, adults with uncomplicated malaria received three administrations of two tablets (100:300 mg AS/AQ) in a 24-h interval, in Democratic Republic of Congo. Parasitemia and fever were measured and the plasma levels of parent compounds and metabolites [dihydroartemisinin (DHA) and monodesethylamodiaquine (MdAQ)] were determined by high-performance liquid chromatography. In addition, we determined the prevalence of molecular markers of resistance to chloroquine (CQ) and sulfadoxine/pyrimethamine (SP). The AS/AQ combination TRIMALACT demonstrated a good efficacy resulting in an excellent clinical and parasitological response rate of 100% after correction for PCR results. Treatment regimen was well tolerated. The main disposition parameters to AS+AQ were: for DHA, AUC = 632 +/- 475 ng h/ml and Cmax = 432 +/- 325 ng/ml, and for MdAQ = 14268 +/- 4114 ng h/ml and Cmax = 336 +/- 225 ng/ml (mean +/- standard deviation). Parasite genotyping show high frequencies of molecular SP- and CQ-resistance markers with more 80% of the samples showing more than three mutations linked to SP resistance and 93.48% carrying parasite with the CQ-resistant haplotype. This study shows that the AS/AQ combination TRIMALACT is safe and effective in the treatment of highly drug-resistant falciparum malaria.

Disposition of 14C-labelled ENDOTELON in humans.

In order to study the disposition of ENDOTELON in humans, this compound was labelled with 14C by photosynthesis. ENDOTELON consists of a complex of procyanidolic oligomers extracted from the seeds of a variety of vine cultivated in the Bordeaux wine-growing region, and is prescribed for the treatment of chronic venous insufficiency and retinal lesions. Considering the difficulty in labelling the various constituents of the product, the labelling procedure was based on providing radioactive CO2 to the plant. After isolation and purification, 150 mg of active material (50 microCi) was administered orally to six healthy volunteers. Radioactivity was measured in the blood over time until 72 and 120 hours in the same subjects after drug administration. Urinary and faecal elimination was measured for a period of 167 hours. Urinary elimination of the radioactive compounds represented 12 to 27% of the administered dose and faecal elimination represented 47 to 75% depending on the subject. The radioactivity of the 14CO2 eliminated in the breath was also measured, and represented around 8% of the total radioactivity for the 72-hour period after administration. Although the disposition of ENDOTELON is based on the total radioactivity measured over time, this technique allows the evaluation of the elimination rate of the product and its metabolites from the human body.

A bioequivalence study of levothyroxine tablets versus an oral levothyroxine solution in healthy volunteers.

Probably for genetic reasons a substantial part of the Greek population requires Levothyroxine treatment. Since commercially available Levothyroxine was first marketed, the manufacture and storage of the drug in tablet form has been complicated and difficult; and as cases of therapeutic failure have frequently been reported following treatment with this medicinal agent, quality control is an essential factor. Due to the unreliability of Levothyroxine-based commercial products, in the present study we decided to follow the Food and Drug Administration (FDA) guidelines*, and use a Levothyroxine solution as reference product. The bioavailability of the Levothyroxine sodium tablet formulation THYROHORMONE/Ni-The Ltd (0.2 mg/tab) and that of a reference oral solution (0.3 mg/100 ml) under fasting conditions were compared in an open, randomized, single-dose two-way crossover study. Twenty four healthy Caucasian volunteers (M/F=15/9, mean age=32.9+/-7.4yr) participated in the study. Bioavailability was assessed by pharmacokinetic parameters such as the area under plasma concentration-time curve from time zero up to the measurable last time point (AUC(last)) and the maximum plasma concentration (Cmax). Heparinized venous blood samples were collected pre-dose and up to a 48-hour period post-dose. Levothyroxine sodium in plasma samples was assayed by a validated electrochemiluninescent immunoassay technique. Statistical analysis showed that the post-dose thyrotropin-stimulating hormone (TSH) levels decreased significantly (p<0.05). Regarding Levothyroxine (T4), the point estimate of the test formulation to the reference formulation ratios (T/R) for AUC(last) and Cmax was 0.92 with 90% confidence limits (0.90, 0.94) and 0.93 with 90% confidence limits (0.91, 0.94), respectively. Regarding triiodo-L-thyronine (T3), the point estimate for the T/R ratios of AUC(last) and Cmax was 0.92 with 90% confidence limits (0.90, 0.95) and 0.94 with 90% confidence limits (0.92, 0.95), respectively. The 90% confidence limits for the pharmacokinetic parameters AUC(last) and Cmax lie within the acceptance limits for bioequivalence (0.80, 1.25), for both T3 and T4.

Pharmacokinetics/Pharmacodynamics findings after repeated administration of ARTESUNATE thermostable suppositories (RECTOCAPS) in Vietnamese patients with uncomplicated malaria.

In recent years, Artemisinin and particularly one of its derivatives--Artesunate (ART--has become an essential alternative for treatment of both uncomplicated and severe falciparum malaria in Asia and Africa as well. Therefore, these compounds are still and inccreasingly in the focus of interest because of quick acting of this drug, is able to help even unconscious to overcome the malaria attack, when administered by injection. As an alternative, RECTOCAPS have been developed and their use is meanwhile well established. From earlier studies in children, suffering from plasmodium falciparum malaria, we obtained a high level of DHART in the blood, but as expected also a rapid decline in the levels of both DHART and ART. A second administration of ART was additionally applied 4 hours after the first administration. DHART and ART plasma levels were found to last longer on an assumed therapeutic level than those obtained after one administration only. The fever clearance and the parasitemia reduction rates were found to be effective according to this dosing regimen. In view of these findings, we decided to conduct the actual described study by administering 200 mg of ART every 3 hours (0, 3, 6 and 9 h) by the rectal route. Soft geiatine capsules (RECTOCAPS) containing 200 mg of ART GMP--type each (Artesunic acid) were administered by rectal route. Each patient received four RECTOCAPS capsules (4 x 200 mg of ART) over a 3 h period. 12 adult patients with uncomplicated malaria were selected. Age, weight, height, body temperature, parasite counts before treatment and their evolution until 96 h are determined. Blood samples were taken at short time intervals after starting with the first medication: 0, 30 min, 60 min, 3 h, 6 h, 9 h, 12 h, 24 h, 36 h, 48 h, 60 h, 72 h, 84 h, 96 h and 108 h. The aliquots of all the blood samples were used for performing parasite counts. Plasma obtained following the traditional procedure was kept at -40 degrees C until analysis. HPLC technique with electrochemical detector was used for quantification of ART and DHART. From the blood concentration values of ART and DHART, the following observation can be derived: the onset of action is observed within the first half hours, therapeutic levels of the drug obtained (89 microg/ml ART compared to 84 microg/ml DHART). The DHART levels are somewhat higher than those of ART (a peak concentration after 6 h starting medication of 151 microg/ml ART as compared to 276 microg/ml DHART). The variations as a function of frequency of DHART uptake are much less marked than those observed for ART. Another finding is that after the administration, some sort of a plateau of DHART and ART is built up, lasting at least from 9 to 12 hours with DHART level of about 190 microg/ml and ART of 90 microg/ml. In the case of single-dose administration, the levels of both compounds were below the detection threshold after three hours. With regard to the parasite counts, although there were inter-individual variations, it should be noted that after 48 hours a high proportion of the patients (8 out of 12) was completely clear of parasites. Similar results were observed with regard to the body temperature (7 out of 12 returned to normal temperature 36 hours after starting the therapy). The findings of the study support the RECTOCAPS application principle resulting in effectiveness both for the velocity of drug uptake as well as for the height of plasma levels. Repeated administration of ART can extend the duration of therapeutic plasma levels of the drug.

Plasma levels of artesunate and dihydroartemisinin in children with Plasmodium falciparum malaria in Gabon after administration of 50-milligram artesunate suppositories.

A thermostable suppository of artesunate (artesunic acid) has been developed. In Gabon, 12 children with Plasmodium falciparum malaria received two administrations of this suppository in a 4-hr interval. Parasitemia and fever were then measured and the plasma levels of artesunate and its active metabolite, dihydroartemisinin, were determined by means of a reversed phase high-pressure liquid chromatography method using reductive electrochemical detection. Substantial parasite clearance (97-100%) was noted 24 hr after the beginning of the treatment and body temperature had returned to normal. Absorption, metabolism, and elimination of artesunate were rapid. Mean values of maximum plasma levels (Cmax) and maximum concentration peak times (tmax) were evaluated. The Cmax of dihydroartemisinin (0.18 +/- 0.10 microg/ml [mean +/- SE]) was higher than the Cmax of artesunate (0.09 +/- 0.04 microg/ml) and the tmax of dihydroartemisinin (1.13 +/- 0.58 hr) was higher than the tmax of artesunate (0.58 +/- 0.19 hr). Plasma levels 30 min after the second suppository administration were not consistently higher than those found 30 min after the first administration.

Determination of N-acetylation phenotyping in a Greek population using caffeine as a metabolic probe.

Studies of isoniazid, the well known antituberculosis drug, have revealed that N-acetylation polymorphism, is of great clinical importance. In humans, N-acetylation is one of the most important pathways in the inactivation of isoniazid. Caffeine, which is also biotransformed by N-acetylation, has been widely used as an in vivo probe for the assessment of N-acetyltransferase polymorphism. The activity of N-acetyltransferase can be estimated from the urinary metabolic ratio of two caffeine metabolites, namely, 5-acetylamino-6-formylamino-3-methyluracil (AFMU), and 1-methylxanthine (1X) after the ingestion of caffeine. In the present study caffeine was used as a metabolic probe to determine N-acetyltransferase polymorphism in 83 healthy Greek volunteers by means of the molar ratio of AFMU and IX determined in urine following ingestion of 200 mg caffeine. Frequency distribution analysis of the metabolic ratios AFMU/1X revealed two distinct groups with 66.3% (n = 55) slow acetylators and 33.7 % (n = 28) rapid acetylators. No statistically significant difference was detected between slow and fast acetylators in terms of gender, smoking habits and caffeine-intake habits. These results are in agreement with previous studies on N-acetyltransferase activity in Caucasians using caffeine as a metabolic probe. They also agree with reports on N-acetyltransferase activity in Greek tuberculosis patients using isoniazid as a metabolic probe. Thus, the use of caffeine as a metabolic probe is a reliable method for the assessment of N-acetyltransferase activity in the Greek population.

Pharmacokinetics of artemisinin and artesunate after oral administration in healthy volunteers.

This study was designed to determine the pharmacokinetic parameters of a new pharmaceutical form of artemisinin (a natural substance extracted from the Artemisia annua L. plant) and of one of its derivatives, artesunate, a semisuccinate of 12-hydroxy-artemisinin. These two compounds are widely used in the treatment of malaria. The new oral forms of these two compounds, in 250-mg tablets, were used in two parallel pharmacokinetic studies. For artemisinin, the mean pharmacokinetic parameters were maximum drug concentration (Cmax) = 0.36 microgram/ml; peak time (tmax) = 100 min; appearance half-life (t1/2 max) = 0.62 hr; distribution half-life (t1/2 alpha) = 2.61 hr; decline half-life (t1/2 beta) = 4.34 hr; and total area under the concentration-time curve (AUC) = 1.19 micrograms.hr/ml. For artesunate, its main metabolite, dihydroartemisinin, was measurable in the plasma. The mean pharmacokinetic parameters for dihydroartemisinin were appearance rate constant (Ka) = 2.11 hr-1; elimination rate constant (Ke) = 1.18 hr-1; biotransformation half-life = 0.33 hr; elimination half-life = 0.65 hr; and AUC = 0.74 microgram.hr/ml. Both pharmaceutical forms were well-tolerated and no undesirable side effects were observed in any of the subjects.

Bioequivalence study of two pharmaceutical forms of rifampicin capsules in man.

In this study the bioavailability of a new pharmaceutical form of rifampicin, Rifampicine Generic (300 mg capsules), was compared to a reference form Rimactan (300 mg capsules). Twelve healthy volunteers participated in a cross-over study. Each dosage form was administered, one after the other, to each subject in the morning after a fasted night period. Both forms were well tolerated and no side effects were observed in any of the subjects during the study. Blood samples were collected over 10 h. The rifampicin plasma concentrations were determined by an HPLC method. The pharmacokinetic parameters, Cmax, Tmax, AUC0-10h (mean +/- SD), were 6.06 +/- 2.95 micrograms/ml, 2.33 +/- 1.60 h, 25.57 +/- 12.6 micrograms.h.ml-1, respectively, for the new form and 6.55 +/- 2.47 micrograms/ml, 2.04 +/- 1.37 h, 26.11 +/- 9.10 micrograms.h.ml-1, respectively, for the reference form. The statistical analysis of different parameters with the Westlake method, ANOVA, and the Wilcoxon test with a probability of 95% showed no differences between the two forms of rifampicin. It was concluded that Rifampicine Generic 300 mg capsules are bioequivalent to Rimactan 300 mg capsules.

Vecuronium neuromuscular blockade reflects liver function during hepatic autotransplantation in pigs.

BACKGROUND: Rapid assessment of hepatic function early after reperfusion of the liver graft is of great importance, because it may allow for prompt detection of incipient hepatic graft failure. The current study was undertaken to determine whether the continuous recording of neuromuscular transmission could be used as an on-line assessment of hepatic function during liver transplantation when a muscle relaxant with high hepatic uptake is used. METHODS: We quantified and compared the effect of liver exclusion and graft reperfusion on the level of vecuronium-induced neuromuscular blockade in nine pigs studied twice within 3 days. During the 1st day (control session), an intravenous infusion of vecuronium was administered to maintain a constant 90-95% twitch depression during 180 min. The twitch response was then allowed to recover spontaneously to 75% of its prerelaxant value. Neuromuscular transmission was continuously measured on the right anterior leg using an acceleration transducer. During the same time period, the metabolic rate of 14C-labeled aminopyrine (a well-established quantitative test of the liver microsomal function) was determined by measuring the excretion of 14CO2 in expired air after administration of an intravenous bolus of 14C-labeled aminopyrine. Two days later, the pigs underwent a hepatic autotransplantation, during which vecuronium was administered to maintain a constant 90-95% twitch depression. After reperfusion of the liver graft, the vecuronium infusion rate was maintained at its anhepatic level, and the recovery index of the neuromuscular blockade (the time from 25% to 75% recovery of twitch height) was calculated. The aminopyrine breath test was performed during the last 30 min of the anhepatic phase, and during 3 h after reperfusion of the liver graft. RESULTS: During control studies, the mean infusion rate of vecuronium was 1.30 +/- 0.33 mg.kg-1.h-1 and the recovery index was 3.4 +/- 0.5 min. During liver dissection, the infusion rate of vecuronium was similar to the control value (1.18 +/- 0.16 mg.kg-1.h-1), then considerably decreased to 0.05 +/- 0.03 mg.kg-1.h-1 during the anhepatic phase. After reperfusion of the liver graft, the recovery index was markedly prolonged to 35.5 +/- 15.8 min, indicating a prolongation of the recovery of neuromuscular blockade by a factor of 10.4. Excretion of 14CO2 was equal to zero during the anhepatic phase and then increased to 0.19 +/- 0.11% during the 1st h after reperfusion of the liver graft, an excretion rate corresponding to 11.2% of control conditions. The relationship between individual changes in the recovery index of the neuromuscular blockade and 14CO2 excretion in expired air after reperfusion of the liver graft showed a strong significant correlation (r2 = 0.71). CONCLUSIONS: These results indicate that, compared with the control studies, there is a similar decrease in the recovery rate of vecuronium-induced neuromuscular blockade and in the metabolic rate of 14C-labeled aminopyrine during the progressive recovery of hepatic function immediately after unclamping of the liver vessels. Metabolism of 14C-labeled aminopyrine increased progressively during the reperfusion phase. Therefore, recording of neuromuscular transmission during liver transplantation could serve as a continuous and easy to perform assessment of liver graft function provided that a muscle relaxant with a high hepatic uptake is used for neuromuscular blockade.

The interaction of artemisinin with red cell membranes.

Artemisinin (qinghaosu) and its derivatives are endoperoxide-containing compounds that are an important new class of antimalarial drugs. Tritiated dihydroartemisinin is taken up and concentrated by isolated red cell membranes but not by intact erythrocytes. More than half of the membrane-associated drug can be released by treatment with phospholipase A2 followed by extraction with ethyl acetate. The remaining drug appears to be bound to the major red cell membrane proteins. There is no association of the drug with either the membrane or cytoplasm of intact red cells. Thus dihydroartemisinin appears to be taken up by isolated membranes, where it associates with proteins but not via intact red cells.

Morphologic effects of artemisinin in Plasmodium falciparum.

Ultrastructural changes induced in Plasmodium falciparum by artemisinin were studied in vitro. Electron microscopic autoradiography was performed on infected erythrocytes that were exposed in vitro to 3H-dihydroartemisinin and 14C-artemisinin. These drugs consistently were located in food vacuoles and mitochondria. Two hours after administration, changes were observed in parasite mitochondria, rough endoplasmic reticulum, and nuclear envelope. At four hours, in addition to the earlier changes, nuclear membranes and, to a lesser extent, some plasma membranes formed myelin figures. In addition, there was a disappearance of ribosomes, and a destruction of food vacuole membranes. These changes may lead to the total disorganization of the parasites. Approximately 30% of the parasites manifested these alterations.

[Aminopyrine breath test in hepatic auto-transplantation in pigs]. / L'aminopyrine breath test (ABT) au cours de l'autotransplantation hépatique chez le porc.

The aminopyrine breath test (ABT) was performed during hepatic autotransplantation in the pig. The test is reproducible in this animal and only hepatic cytochromes perform the demethylation of aminopyrine. Ischemia, varying from 90 to 200 minutes, generated a major decrease in the elimination of the 14CO2 and a marked change in the elimination curve. In this specific model it was not possible to assess survival of the animal by the ABT.

Pharmacokinetics of arteether in dog.

A pharmacokinetic study has been conducted in six beagle dogs after i.m. administration of 25 mg/kg of arteether, a qinghaosu (artemisinin) derivative of high anti-malarial activity. Arteether plasma concentrations were measured during a 24 h period using HPLC with an electrochemical detector in the reductive mode. The pharmacokinetic parameters were established using an open two-compartment model. Results showed a relatively rapid absorption phase: T1/2ka was 0.300 +/- 0.096 h and a mean elimination half-life of 27.95 +/- 11.93 h. Cmax was 110 +/- 16 ng/ml, Cltot/F was 1.69 +/- 0.34 ml/min and AUC was 2797 +/- 476 ng/ml/h.

Dose requirements and plasma concentrations of pipecuronium during bilateral renal exclusion and orthotopic liver transplantation in pigs.

We have studied five pigs undergoing bilateral clamping of the renal pedicles, seven pigs undergoing orthotopic liver transplantation and three control animals without surgery in order to examine the roles of the kidney and liver in the plasma clearance of pipecuronium. An i.v. infusion of pipecuronium was controlled to maintain a constant 90-95% twitch depression throughout the investigation. The right sciatic nerve was stimulated continuously with supramaximal stimuli at 0.1 Hz and the force of the corresponding evoked isometric muscle contraction was recorded continuously. Control pigs needed an infusion rate of pipecuronium 8-10.7 micrograms kg-1 min-1. In the renal group, it was necessary to reduce the infusion rate of pipe-curonium by about 25% after clamping both renal vascular pedicles (P less than 0.05 compared with controls); in pigs undergoing liver transplantation, it was necessary to reduce the rate by approximately 80% after clamping hepatic vessels (P less than 0.05 compared with controls and from the period after clamping of renal vessels). After hepatic recirculation, the infusion rate of pipecuronium was increased progressively to a rate which corresponded to 50% of baseline values (P less than 0.05 compared with the anhepatic phase and from controls). Plasma concentrations of pipecuronium were comparable in the three animal groups and did not change significantly during the study. These data suggest that the liver plays a more important role than the kidney in the plasma clearance of pipecuronium in pigs.

Plasma concentrations of laudanosine, but not of atracurium, are increased during the anhepatic phase of orthotopic liver transplantation in pigs.

To quantify the changes in plasma concentrations of atracurium and laudanosine induced by the lack of hepatic function and circulation, the authors studied nine domestic pigs (22-25 kg) undergoing an orthotopic liver transplantation, and three control animals without surgery, using atracurium as the muscle relaxant. After intubation facilitated by isoflurane 2-3%, anesthesia was maintained with isoflurane (0.5% in oxygen) and fentanyl (4 micrograms.kg-1.hr-1). Ventilation was controlled to keep end-tidal CO2 at 35-40 mmHg, body temperature maintained at 35.5-37.5 degrees C, and arterial pH at 7.35-7.50. The right sciatic nerve was stimulated with a nerve stimulator delivering a single twitch at 0.1 Hz with 0.2-ms duration, at supramaximal stimulation. The force of the corresponding evoked isometric muscle contraction was continuously measured by a force-displacement transducer. A single iv bolus of atracurium (2 mg/kg) was given to obtain a 90-95% twitch depression, followed 5 min later by a constant-rate iv infusion of atracurium at 120 micrograms.kg-1.min-1 maintained during the entire investigation. Blood samples for plasma atracurium and laudanosine concentrations were drawn every 15 min. In the control group, plasma concentrations of atracurium remained stable between 6.5-8.0 micrograms/ml following initial bolus injection; plasma concentrations of laudanosine increased during the first 60 min, then remained stable between 0.69-0.74 micrograms/ml up to the end of the study. In animals undergoing transplantation, plasma concentrations of atracurium remained stable between 10-12 micrograms/ml, despite a 90-min duration of liver exclusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacokinetics of atracurium besylate in the pig after a single i.v. injection.

A pharmacokinetic study of atracurium besylate was performed in the pig after a single i.v. bolus injection of 2 mg/kg, the dose needed to produce surgical neuromuscular blockade. The plasma concentration values were obtained by high performance liquid chromatography. Using a two-compartment pharmacokinetic model, the elimination half life was found to be 28.6 +/- 6.3 min (mean +/- SEM), the total volume of distribution 341 +/- 56 ml/kg and the plasma clearance 8.7 +/- 1.1 ml/min/kg. Although the doses required to obtain a satisfactory neuromuscular blockade as well as the plasma level, volume of distribution and plasma clearance values were higher in the pig than in man, the distribution and elimination half-lives were similar to those recently reported.

Autoradiographic study of 14C-sulpiride in monkey.

Substituted benzamides have been the object of numerous metabolic studies including many by whole body autoradiography of rats and mice. The present study reports autoradiographic data concerning 14C-labelled Sulpiride in monkey. The Study was limited to the brain in order to elucidate the controversial question as to whether the drug can cross the blood-brain barrier. The results showed that in monkey, as in rat and mouse, there is no localization in the brain as can be clearly seen on the autoradiograms. In view of these results and of the undeniable neuroleptic properties of Sulpiride, an indirect mode of action through the release of endogenous mediators is proposed.