Artemisinins are known for their low aqueous solubility and resultant poor and erratic absorption upon oral administration. The poor solubility and erratic absorption usually translate, to low bibavailability. Enzymatic degradation and physiological barriers are also amongst the challenges which must be overcome to ensure effective delivery. Artemisininbased monotherapy and combination therapies are essential for the management and treatment of uncomplicated as well as cerebral malaria. Artemisone and artemiside are novel artemisinin derivatives, their antimalarial activity/efficacy was evaluated in vitro and in vivo in the presence and absence of Pheroid™ technology. Pheroid™ technology is a patented drug delivery system which has the ability to capture, transport and deliver pharmacologically active compounds. Pharmacokinetic models were also constructed for artemis one and artemiside, both in the presence and absence of Pheroid™ technology.
Results obtained with the jn vitro antimalarial activity evaluation indicated that artemiside was slightly more potent than artemisone and much more potent than artesunate. Artemiside had IC50 values of 0.54 ± 0.03 nM (reference) and 0.10 ± 0.05 nM (Pheroid™) (p = 0.009) while artemisone had values of 0.94 ± 0.04 nM (reference) and 0.21 ± 0.04 nM (Pheroid™) (p = 0.0001). Artesunate had IC50 values of 29.65 ± 0.05 nM (reference) and 10.20 ± 0.04 nM (Pheroid™) (p < 0.0001).
Results obtained with the in vivo antimalarial activity evaluation indicated that artemisone led to more favourable treatment outcomes than artemiside. The Peters' 4-day suppressive test was used as a basis model. With artemisone treatment recrudescence occured at 16 days post infection at a dose of 20.0 mg/kg bodyweight and at 12 days post infection at 2.5 mg/kg bodyweight. With artemiside recrudescence occurred at 8 days post infection with both the 10.0 mg/kg and 2.5 mg/kg bodyweight treatment regimens. When comparing the antimalarial effect of the drugs with and without Pheroid™ technology there was no significant difference in terms of parasite reduction or in the achieved treatment outcomes of either compounds.
The pharmacokinetic parameters were evaluated in a mouse model where C57 BL6 mice were used. The compounds were administered at a dose of 50.0 mg/kg bodyweight via an oral gavage tube at a volume of 200 µl. Blood samples were collected by means of tail bleeding. Sensitive and selective LC/MS/MS methods were developed to analyze the drug concentrations in the plasma samples. The relative bioavailability of artemisone was RA = 1.0 (reference) and RA = 4.57 (Pheroid™) (p < 0.001). The absolute bioavailability was calculated as F = 0.10 (reference) and F = 0.48(Pheroid™) (p < 0.001). The boiavailability of artemiside was not dramatically enhanced by the Pheroid™ delivery system. / Thesis (Ph.D. (Pharmaceutics))--North-West University, Potchefstroom Campus, 2010.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:nwu/oai:dspace.nwu.ac.za:10394/4985 |
| Date | January 2009 |
| Creators | Steyn, Johan Dewald |
| Publisher | North-West University |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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