Formulation and Monitoring the Stability of Artesunate in Artesunate – Amodiaquine Combination Tablets

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In this work, a single dosage form of artesunate and amodiaquine was formulated. Each dosage form contains 100mg of artesunate and 300mg of amodiaquine constituting two tablets daily and a total of six tablets for three days for the full dose of adults in the treatment of malaria. A simple, accurate and precise isocratic reverse phase HPLC method with a mobile phase comprising 0.3% v/v of glacial acetic acid, acetonitrile and triethylamine in the ratio of 55%: 45%: 0.3% was developed using a C8 column. The final pH was always in the range of 4.5±0.1. A flow rate of 2.0ml/min with UV detection set at 254nm was employed at room temperature. Artesunate had a retention time of 4.13 minutes and amodiaquine had a retention time of 5.93 minutes. A linear calibration curve was obtained with r2 value of 0.998. Relative standard deviation (RSD) obtained was less than 1% indicating a high precision of the method. The method proved to be robust with variations in the mobile phase and stationary phase compositions. The limit of detection of artesunate and amodiaquine are 1.29x10-4 %w/v and 3.3x10-5 %w/v respectively. The limit of quantification of artesunate and amodiaquine are 6.45x10-4 %w/v 1.65x10-4 %w/v respectively. The shelf – life of the artesunate in the artesunate – amodiaquine combination tablets is 0.41 years or 4.8 months at 28oC and 0.1 years or 1.2 months at 40oC. Artesunate – amodiaquine combination tablets were found to have a short stability period. Artesunate and amodiaquine are incompatible, and there is severe degradation of the drugs in presence of each other.