A comparison of the stage-specific efficacy of chloroquine, artemether and dioncophylline B against the rodent malaria parasite Plasmodium chabaudi chabaudi in vivo.

Chloroquine, artemether and dioncophylline B efficacy against Plasmodium chabaudi was compared. One intraperitoneal injection (10 mg/kg body weight) was given daily over 3 consecutive days to OF1 mice when they were predominantly bearing ring, trophozoite and schizont forms. The parasitaemia was monitored every 2 h during two schizogonic cycles and daily thereafter until parasites were cleared. Chloroquine was more efficient at the trophozoite stage, while artemether was effective against all erythrocytic stages, with a marked efficacy against the trophozoite stage. Chloroquine-treated and artemether-treated parasites displayed a pigment-clumping morphology and lowered the parasitaemia faster than dioncophylline B. Dioncophylline B was effective at trophozoite and schizont stages, but completely ineffective at the ring stage. These results demonstrate that a better timing of drug administration increases the efficacy of common and new antimalarial drugs and provides a model for antimalarial-action monitoring. Drug-induced changes in infected erythrocyte morphology are presented.

Development and optimisation of a flow injection assay for fluticasone propionate using an asymmetrical design and the variable-size simplex algorithm.

A flow injection analysis method is described to determine fluticasone propionate, based upon a novel adaptation of the reaction of o-phthalaldehyde with a thiol and a primary amine. The method, which allows both UV and fluorescence detection, has been optimised using experimental design. First a screening is executed to select the significant factors and in a second step these factors are optimised with the variable-size simplex algorithm. In the screening step, a two-level fractional factorial design is compared with an asymmetrical design containing the same number of experiments, but in which one factor is at three levels. It was found that in both designs the same significant variables are detected for the two-level factors, but that for the three-level factor the asymmetrical design confirms an expectation of having a (local) optimum in the examined domain, whilst from the two-level design this is not at all apparent. Complete optimisation was carried out for both UV and fluorescence detection. The two detection methods did not have the same significant variables. For the UV detection, the temperature and the pH adjustment on-line (concentration of sodium hydroxide and amount of boric acid) were the most critical parameters. For the fluorimetric detection the temperature and the fraction of methanol were critical. Moreover the conditions found to be optimal are different for both detection methods.

Fast development of separation methods for the chiral analysis of amino acid derivatives using capillary electrophoresis and experimental designs.

The use of experimental design in method development was studied for the chiral separation of several amino acid derivatives with capillary electrophoresis. The aim of this study was to define rapidly experimental conditions under which the enantiomers can be sufficiently separated for quantification and to derive a methodology for the separation of new compounds. Three modified cyclodextrins (CDs) were used as chiral selectors: hydroxypropyl-beta-cyclodextrin, carboxymethyl-beta-CD and sulfobutylether-beta-CD. The following factors were examined: the type of cyclodextrin, the CD concentration, the pH and the % of organic modifier (methanol) of the electrolyte. Two types of fractional factorial design were used depending on the type of analyte and on the number of factors selected: a 3(4-2) fractional factorial design (4 factors studied at 3 different levels) and a 2(3-1) fractional factorial design (3 factors at 2 different levels). From the 14 compounds investigated, 12 could be separated with one or another CD and not more than 9 experiments were required. No generalisation of the best analysis conditions was possible within this family of compounds. Specific analysis conditions must be defined for each analyte. Experimental designs have shown to be very useful to determine rapidly conditions under which each enantiomer can be separated with an acceptable resolution.

Separation from related compounds and assay of calcipotriol by high-performance liquid chromatography.

In this paper, two methods are presented. One involves the separation of calcipotriol, a new synthetic analogue, from two related compounds, specifically cholecalciferol (Vitamin D3) and calcitriol (1,25-dihydroxyvitamin D3). The other involves the isolation and assay of calcipotriol from a topical ointment. The study was performed with reversed-phase high-performance liquid chromatography using an RP18 column and ultraviolet detection. Applying the method of Snyder, a mobile phase mixture containing methanol-acetonitrile-water (67:23:10, v/v) was found which achieved a total separation within 18 min. A mobile phase of methanol-water (80:20, v/v) attained a slower elution of calcipotriol. For isolation and assay of calcipotriol from an ointment (Daivonex), dissolution in chloroform gave the highest recovery (> 98%). The isolation and assay process can be performed within 2 h.

A ruggedness test strategy for procedure related factors: experimental set-up and interpretation.

A strategy to perform ruggedness tests for mainly procedure related factors is described. The different steps in the set-up of the experiments and in the interpretation of the results are given. The described strategy is based on a number of case studies and allows a statistical interpretation of the significance of the effects. It was implemented in a software tool. This original strategy was completed with a number of minimal screening designs which reduce the number of experiments to perform, but in consequence only allow a limited or no statistical interpretation of the effects. Some of the minimal designs are expandable to designs with characteristics similar to those of the original strategy.

Optimisation of the reversed phase liquid chromatographic separation of atovaquone, proguanil and related substances.

The optimisation of the separation of the antimalarial drugs, proguanil and atovaquone and six related compounds was obtained by two independent optimisation steps; the optimisation of the mobile phase composition and the optimisation of the pH. This was done using window selection diagrams (WSD) and a mixture design. The optimal conditions allow the identification of the six related compounds down to 0.1%.

Ruggedness tests on the high performance liquid chromatography assay of the United States Pharmacopoeia 23 for tetracycline.HCl: comparison of different columns in an interlaboratory approach.

Ruggedness tests were performed on the United States Pharmacopoeia assay for tetracycline.HCl to examine problems previously reported in the literature. The experiments were performed on nine different columns. The effects of four factors selected from the procedure were examined on qualitative responses by performing half-fraction factorial designs at three different ages on each column. The influence of column ageing was separately evaluated by injections under nominal method conditions at different ages. The C-8 columns gave a separation that was as good as, or better than, the C-18 ones and were less influenced by ageing. The normalized effects of each of the factors on a response were compared and found to be more or less equal for most of the columns and to remain constant with time. The responses were most affected by the pH of the mobile phase and by the content of the organic modifier. In general it was found that C-8 columns were preferred for this assay.