Efficacy enhancement of the antimalarial drugs, mefloquine and artesunate, with PheroidTM technology / E. van Huyssteen
Van Huyssteen, Este
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Malaria is currently one of the most imperative parasitic diseases in developing countries. Artesunate has a short half-life, low aqueous solubility and resultant poor and erratic absorption upon oral administration, which translate to low bioavailability. Mefloquine is eliminated slowly with a terminal elimination half-life of approximately 20 days and has neuropsychiatric side effects. Novel drug delivery systems have been utilised to optimise chemotherapy with currently available antimalarial drugs. Pheroid™ technology is a patented drug delivery system which has the ability to capture, transport and deliver pharmaceutical compounds. Pheroid™ technology may play a key role in ensuring effective delivery and enhanced bioavailability of novel antimalarial drugs. The aim of this study was to evaluate the possible efficacy and bioavailability enhancement of the selected antimalarial drugs, artesunate and mefloquine, in combination with Pheroid™ vesicles. The in vitro efficacy of artesunate and mefloquine co-formulated in the oil phase of Pheroid™ vesicles and entrapped in Pheroid™ vesicles 24 hours after manufacturing were investigated against a 3D7 chloroquine-sensitive strain of Plasmodium falciparum. Parasitemia (%) was quantified with flow cytometry after incubation periods of 48 and 72 hours. Drug sensitivity was expressed as 50% inhibitory concentration (IC50) values. An in vivo bioavailability study with artesunate and mefloquine was also conducted in combination with Pheroid™ vesicles, using a mouse model. A sensitive and selective liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed to analyse the drug levels. C57 BL6 mice were used during this study. The selected antimalarial drugs were administered at a dose of 20 mg/kg with an oral gavage tube. Blood samples were collected by means of tail bleeding. The in vitro drug sensitivity assays revealed that artesunate, co-formulated in the oil phase of Pheroid™ vesicles and evaluated after a 48 hour incubation period, decreased the IC50 concentration significantly by 90%. Extending the incubation period to 72 hours decreased the IC50 concentration of artesunate, also co-formulated in the oil phase of Pheroid ™ vesicles significantly by 72%. No statistically significant differences between the reference and Pheroid™ vesicle groups were achieved when artesunate was entrapped 24 hours after manufacturing of Pheroid™ vesicles. Mefloquine co-formulated in the oil phase of Pheroid™ vesicles and evaluated after a 48 hour incubation period decreased the IC50 concentration by 36%. Extending the incubation period to 72 hours increased the efficacy of the Pheroid™ vesicles and the IC50 concentration was significantly decreased by 51%. In contrast with the results obtained with artesunate, entrapment of mefloquine in Pheroid™ vesicles 24 hours after manufacturing decreased the IC50 concentration significantly by 66%. The LC-MS/MS method was found to be sensitive, selective and accurate for the determination of artesunate and its active metabolite, dihydroartemisinin (DHA) in mouse plasma and mefloquine in mouse whole blood. Most of the artesunate plasma concentrations were below the limit of quantification in the reference group and relatively high outliers were observed in some of the samples. The mean artesunate levels of the Pheroid™ vesicle group were lower compared to the reference group, but the variation within the Pheroid™ vesicle group lessened significantly. The mean DHA concentrations of the Pheroid™ vesicle group were significantly higher. DHA obtained a higher peak plasma drug concentration with the Pheroid™ vesicle group (173.0 ng/ml) in relation to the reference group (105.0 ng/ml) and at a much faster time (10 minutes in Pheroid™ vesicles in contrast to 30 minutes of the reference group). Pharmacokinetic models could not be constructed due to blood sampling per animal limitation. The incorporation of mefloquine in Pheroid™ vesicles did not seem to have improved results in relation to the reference group. No statistical significant differences were observed in the pharmacokinetic parameters between the two groups. The relative bioavailability (%) of the Pheroid™ vesicle incorporated mefloquine was 7% less bioavailable than the reference group.
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