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.

[Relative bioavailability of an optimised galenical formulation of mefloquine]

The bioequivalence of an optimised formulation of a generic mefloquine (Mephaquin Lactabs/Test) compared to the reference product under fed conditions was assessed in a GCP/ICH conformable study. A standard two-way randomised crossover design with a 9 week washout period between treatments was used. Blood samples for determination of mefloquine concentrations for calculation of Cmax and AUC were collected at pre-dose and at predefined intervals up to 2016 hours after administration of a single oral dose of 750 mg. A standard bioequivalence analysis was performed on the two one-sided t-test procedure for log-transformed Cmax and AUC. 90% confidence intervals were calculated for both parameters and evaluated against regulatory standards of 80-125% (T/R). Analysis of plasma for mefloquine concentration was performed using a validated LC/MS method with MS detection. The ratio of mean AUC and Cmax (T/R) was 1.015 and 1.044, respectively. The 90% confidence intervals were 95.8-109.3% for AUC and 98.2-110.5% for Cmax. Mephaquin produces plasma concentrations comparable to those after administration of the reference product. The 90% confidence intervals for AUC and Cmax are within the acceptable ranges for bioequivalence of 80-125%. Thus, the optimised galenical formulation of Mephaquin Lactabs is bioequivalent to the reference product.

A clinical trial of combination of artesunate and mefloquine in the treatment of acute uncomplicated falciparum malaria: a short and practical regimen

The difficulties in treating drug-resistant falciparum malaria in Thailand are compounded by the necessity of giving antimalarials over long periods of time. The resultant fall in patient compliance not only lowers cure rates but also predisposes to the further spread of drug-resistance. Sequential treatment with artesunate given over 5 days followed by mefloquine produced 100% cure rates in previous study, but might not be a suitable regimen for field treatment. We conducted a clinical trial of a combination of artesunate and mefloquine given twice daily for 2 days in 150 patients with acute uncomplicated falciparum malaria. The dose of artesunate (200 mg) and mefloquine (312.5 mg) were given simultaneously in a separate package. All patients were admitted to a hospital in Bangkok for 28 days to exclude re-infection and monitor the possible adverse effects. One hundred and thirty patients completed the study with 28 days follow up. Twenty patients (13%) left the hospital prior to completion of follow-up for reasons unrelated to their treatment. Cure rate was 97% (126/130). There were no RII or RIII failures and all four patients with treatment failures were of the RI type. The mean parasite clearance time and fever clearance time were 46.4 and 42.5 hours, respectively. All patients were tolerated the combination drugs well and there were no serious toxic adverse reactions. The results indicate that combination of artesunate and mefloquine given twice daily for 2 days is effective and well tolerated in patients with acute, uncomplicated falciparum malaria and suitable as an alternative treatment for multidrug resistant falciparum malaria.

Bioequivalence and relative bioavailability of a new diltiazem sustained release formulation

The bioequivalence and relative bioavailability of a new sustained release formulation of diltiazem (120 mg, Diltiazem-Mepha 120 retard, CAS 33286-22-5) in comparison with a 120 mg reference formulation was investigated in a randomised 2-way cross-over study in 18 healthy volunteers following multiple, twice daily dosing for 5 days. Blood samples were taken prior to the morning dose on days 1 to 4 and before and periodically during 32 h after the last administration in the morning of day 5. The diltiazem concentration was determined using a HPLC method. The following primary and secondary pharmacokinetic parameters were derived from the individual plasma concentration time courses on day 5:Cmax and AUC tau (primary parameters) and PTF,PTS, t1/2, tmax and F(rel) (secondary parameters). For the new test formulation mean (SD) Cmax was 168.9 (49.1) ng/ml and AUC tau was 1343 (313) ng . h/ml, whereas these values were 194.7 (44.2) ng/ml and 1460 (444) ng . h/ml for Cmax and AUC tau of the reference formulation, respectively. Smaller inter-subject variations of the diltiazem plasma concentrations following administration of the test formulation were found, which could be due to an improved retardation principle. However, the point-estimate and 90% confidence interval around the point-estimate fall inside the bioequivalence acceptance range of 0.70-1.43 for Cmax and 0.80-1.25 for AUC tau. Therefore, from the results of this study it can be concluded that the test formulation is bioequivalent with the reference formulation following multiple dose, twice daily administration.

Quantitative cryomicroscopic analysis of intracellular freezing of granulocytes without cryoadditive

Purified human granulocytes were frozen in isotonic saline at different constant cooling rates down to -60 degrees C and subsequently thawed on the thermally defined cryostage of a cryomicroscope. Cells monitored on videotape were examined with respect to cooling rate threshold, type, and temperature of intracellular ice formation during cooling and recrystallization during warming. Two apparently different mechanisms of intracellular ice formation (iif) were distinguished during cooling, i.e., "twitching" (no visible ice front) and "darkening" (diffuse ice front). Both types of iif are related to cooling rate and hence also to dehydration. Cooling rate thresholds and temperatures of intracellular recrystallization were determined. It was found that twitching iif occurs just about 6.3 to 7.4 degrees C above the homogeneous nucleation temperature, suggesting that it might be catalyzed by nucleators present within the cells. Darkening iif, on the other hand, was observed at much higher temperatures, i.e., 23.4 to 28.3 degrees C above the homogeneous nucleation temperature, which could possibly indicate a nucleation induced by extracellular ice crystals (at a cooling rate of 30 degrees K/min, however, darkening iif was observed to occur at a temperature lower than that required for twitching iif). The proposed mechanisms of cryoinjury are related to membrane integrity measurements presented in M. W. Scheiwe, Ch. Körber, and S. Englich, Cryo-Letters, 5, 300-306, 1984.

Low temperature light microscopy and its application to study freezing in aqueous solutions and biological cell suspensions

The freezing of biological cell suspensions can be understood in terms of ice formation in the external suspension medium and the cellular reactions to the changing environment. Cryomicroscopy allows a quantitative analysis of both categories of phenomena. Besides freezing stages of appropriate thermal design, the components used for that purpose include a microcomputer (PSI 80) based control system, an image analysis system (Intellect 100) and a spectrophotometer (MPV compact). The investigation of extracellular ice formation is focused on the following effects: The redistribution of solutes in the residual liquid and the resulting concentration profiles are determined photometrically or densitometrically. The transitions between various morphologies of the ice-liquid phase boundary (planar-cellular-dendritic) can be related to interface instability theories. With respect to solute segregation, the studies also involve the formation of bubbles from supersaturated gaseous solutes and freezing potentials resulting from the differential incorporation of cations and anions into the solid phase. The interaction between particles or cells and the advancing ice front is determined from critical interface velocities marking the transition between repulsion and entrapment. The effects of freezing on biological cells are studied mainly with blood cells, especially lymphocytes. The water efflux due to osmotical gradients across the membrane yields volume shrinkage curves which are recorded and analysed from video images for various cooling rates. Beyond a certain threshold cooling rate, intracellular ice starts to form, and different crystallization morphologies can be detected. The intracellular crystallization temperatures depend on cooling and warming rates as well as on the presence of penetrating cryoadditives. A fluorescence viability is used to determine the percentage of damaged cells immediately after thawing.

Fc receptors and human T lymphocytes in frozen-thawed peripheral blood cells

The present study was carried out to investigate the influence of cryopreservation on human T-cell subsets defined by their membrane receptors for Fc IgM (TM) and Fc IgG (TG) and by their membrane antigens. For this purpose isolated T cells, obtained by neuraminidase-treated sheep erythrocyte (E-N) rosetting, and enriched mononuclear cells were cryopreserved using a programmed freezing procedure. A significant decrease of the TM and TG cells was found whereas the proportion of T cells and their subsets determined by monoclonal antibodies seemed not to be influenced. The effectiveness of T-cell separation by E-N rosetting of frozen lymphocytes demonstrated no impairment of the E-receptor binding capacity of T cells. The PHA reactivity of separated T cells was maintained after cryopreservation; however, the spontaneous blastogenesis was reduced significantly. The selective loss of the TM and TG cells seemed to be dependent on the length of the phase transition time; over 90 sec the capacity of the expression of Fc receptors was profoundly affected. Neither an additional 20 hr incubation after hypotonic shock prior to cryopreservation nor incubation after thawing could repair this function of T cells. The data suggest irreversible damage of the Fc receptor expression capacity on the cell membrane as a result of a disturbance of metabolic pathways rather than a preferentially greater sensitivity of these cells to cryopreservation.

Thermally defined cryomicroscopy and thermodynamic analysis in lymphocyte freezing

A cryomicroscope is described which provides the possibility of quantifying the volume loss of cells during freezing, detection of intracellular ice formation during cooling and warming, as well as the determination of viability as function of (constant) cooling rates. The basic mechanisms occurring in cryopreservation have been studied with this system using the human lymphocyte suspended in pure saline as a biological model system; experimentally observed exosmosis during freezing is compared to predictions from a thermodynamic model. Cell volume loss during freezing has been determined experimentally for cooling rates of 2.4, 12, 48, and 120 degrees K/min. Exosmosis also was calculated corresponding to various assumptions regarding the concentration dependence of the hydraulic permeability of the cells. Further calculations of exosmosis are performed for determining the effects of the initial cell volume. The temperatures and transition cooling rate ranges of intracellular ice formation have been determined. On the basis of exosmosis and a lethal level of intracellular salt concentration, a hypothetical relative optimum of the cooling rate is theoretically predicted and compared to the experiments.

Basic investigations on the freezing of human lymphocytes

Human lymphocytes were frozen at constant cooling rates in the range 2.4 to 1000 degrees K/min without cryoadditive on the cold stage of a thermally defined cryomicroscope. The volume loss due to water efflux was quantified optically for the cooling rates 2.4, 12, 48, and 120 degrees K/min. The likelihood of the formation of intracellular ice was determined as function of the cooling rate. Intracellular crystallization temperatures were obtained for ice formation during both cooling and rewarming. A theoretical analysis of the cell volume loss during freezing was compared to the experimental data and used for an indirect determination of the water permeability of the cells. A relative optimum of the cooling rate is predicted theoretically under the assumption of a critical level of intracellular salt concentration near the eutectic temperature. The dependence of survival and cooling rate was determined cryomicroscopically by simultaneously applying the FDA/EB fluorescence viability test. The optimal cooling rate of about 35 degrees K/min was also found for 2-ml samples frozen within the range of cooling rates of interest. The results show that for freezing in physiological saline solution (1) the optimum of the cooling rate is theoretically predictable, (2) cryomicroscopical data are significant for freezing of samples of larger volume, and (3) the lethal type of intracellular crystallization is cooling rate dependent and distinguishable from innocuous types.

Thermally defined cryomicroscopy and some applications on human leucocytes

A freezing-stage has been developed for use on a standard light-microscope, which can provide reproducible, precisely linear cooling and warming rates in the range from 0.1 to 10,000 K/min. Biological cells in aqueous solutions can be observed during the freeze-thaw cycle; the volume loss due to osmotic efflux of water and the intracellular crystallization of water are detected by video-monitoring. The temperature field generated in the observed samples is comparable to extended cylindrical probes and allows the transfer of cryomicroscopic data to technically used vial geometries. Lymphocytes and granulocytes were observed during freezing using the system described. They were separated and washed, and then frozen on the cold stage of the cryomicroscope at cooling rates ranging from 2 to 500 K/min. Shrinkage of the cells was observed up to 100 K/min and intracellular ice formation could be detected starting at 10 K/min. The results show that human leucocytes show excessive shrinkage up to 36% of their initial volume; the probability of intracellular ice formation exhibits a sharp increase from 10 to 100 K/min where nearly all cells contain ice.