Fixed artesunate–amodiaquine combined pre-formulation study for the treatment of malaria

Artemisinin-based combination therapies, including artesunate (AS) + amodiaquine (AQ), are the currently recommended first-line treatment of uncomplicated falciparum malaria. Fixed-dose co-formulations offer logistic and adherence advantages. This paper reports the initial research phase of the pre-development process of an AS–AQ formulation, further developed by the Drug for Neglected Diseases Initiative (DNDi). Results demonstrate that AS and AQ are not compatible, and AS degradation is related to three main parameters: water content (>1%), elevated temperature (80 °C in dry condition) and possibly the 4-aminoquinoline moiety. Furthermore, AS and AQ incompatibility led to AS degradation and pharmaco-technical changes in classical wet granulation tablets. Both active principles are stable as dry powders. These investigations led to further development of various co-formulations, including the bilayer tablet currently on the market.