Kashyap Patel1, Kevin T Batty2, Brioni R Moore3, Peter L Gibbons4, Carl M Kirkpatrick5. 1. Centre for Medicine Use and Safety, Monash University, Melbourne, VIC, Australia kashyap.patel@monash.edu. 2. School of Pharmacy, Faculty of Health Sciences, Curtin University, Bentley, WA, Australia West Coast Institute, Joondalup, WA, Australia. 3. School of Medicine and Pharmacology, University of Western Australia, Crawley, WA, Australia. 4. School of Pharmacy, Faculty of Health Sciences, Curtin University, Bentley, WA, Australia Department of Medical Technology & Physics, Sir Charles Gairdner Hospital, Nedlands, WA, Australia. 5. Centre for Medicine Use and Safety, Monash University, Melbourne, VIC, Australia.
Abstract
OBJECTIVES: To develop a mechanism-based model that describes the time course of the malaria parasite in infected mice receiving a combination therapy regimen of dihydroartemisinin and piperaquine. METHODS: Total parasite density-time data from Swiss mice inoculated with Plasmodium berghei were used for the development of population models in S-ADAPT. The mice were administered a single intraperitoneal dose of 30 mg/kg dihydroartemisinin, 10 mg/kg piperaquine phosphate or a combination of both antimalarials at 64 h post-inoculation. In a separate study, mice received multiple dihydroartemisinin doses (5 × 10 mg/kg or 30 mg/kg dihydroartemisinin followed by two 10 mg/kg doses). Parasite recrudescence after treatment was defined using a model that incorporated each erythrocytic stage of the P. berghei life cycle. RESULTS: The disposition of dihydroartemisinin and piperaquine was described by a one-compartment and two-compartment model, respectively. The estimated clearance was 1.95 L/h for dihydroartemisinin and 0.109 L/h for piperaquine. A turnover model described the parasite killing curve after single-agent dosing, with an estimated mean IC50 of 0.747 μg/L for dihydroartemisinin and 16.8 μg/L for piperaquine. In addition, the rate of parasite killing by dihydroartemisinin was almost 50-fold faster than for piperaquine. Parameters from the monotherapy models adequately described the parasite density-time curve following dihydroartemisinin/piperaquine combination therapy or multiple-dose regimens of dihydroartemisinin. CONCLUSIONS: This study has developed mechanistic models that describe the parasite-time curve after single, multiple or combination dosing of antimalarials to mice. These structural models have potential application for pre-clinical investigations to design and refine artemisinin-based combination therapy dosage regimens.
OBJECTIVES: To develop a mechanism-based model that describes the time course of the malaria parasite in infected mice receiving a combination therapy regimen of dihydroartemisinin and piperaquine. METHODS: Total parasite density-time data from Swiss mice inoculated with Plasmodium berghei were used for the development of population models in S-ADAPT. The mice were administered a single intraperitoneal dose of 30 mg/kg dihydroartemisinin, 10 mg/kg piperaquine phosphate or a combination of both antimalarials at 64 h post-inoculation. In a separate study, mice received multiple dihydroartemisinin doses (5 × 10 mg/kg or 30 mg/kg dihydroartemisinin followed by two 10 mg/kg doses). Parasite recrudescence after treatment was defined using a model that incorporated each erythrocytic stage of the P. berghei life cycle. RESULTS: The disposition of dihydroartemisinin and piperaquine was described by a one-compartment and two-compartment model, respectively. The estimated clearance was 1.95 L/h for dihydroartemisinin and 0.109 L/h for piperaquine. A turnover model described the parasite killing curve after single-agent dosing, with an estimated mean IC50 of 0.747 μg/L for dihydroartemisinin and 16.8 μg/L for piperaquine. In addition, the rate of parasite killing by dihydroartemisinin was almost 50-fold faster than for piperaquine. Parameters from the monotherapy models adequately described the parasite density-time curve following dihydroartemisinin/piperaquine combination therapy or multiple-dose regimens of dihydroartemisinin. CONCLUSIONS: This study has developed mechanistic models that describe the parasite-time curve after single, multiple or combination dosing of antimalarials to mice. These structural models have potential application for pre-clinical investigations to design and refine artemisinin-based combination therapy dosage regimens.
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