Assessment of absorption and distribution of artemether in rats using a thin layer chromatography scanning technique

TLC scanning technique was found to have good specificity for studying the absorption and distribution of artemether in rats. Plasma or tissue homogenates 0.2-1.0 ml were placed in glass extraction tubes and water was added to make 1.0 ml. Each sample was extracted 3 times with 4 ml mixed organic solvent (n-pentane: dichloromethane = 1:1, vol:vol). The organic layers of 3 extractions were combined and evaporated. The residue was dissolved in 100-300 microliters of ethylacetate and spotted on TLC plates. The chromatogram was developed in solvent system consisting of petroleum ether: chloroform: ethylacetate (4:2:1). The color developing agent was 0.25 g p-dimethylaminobenzaldehyde dissolved in a mixture of 2.25 ml 85% phosphoric acid, 47.6 ml of acetic acid and 20 ml of water. Artemether fat emulsion was given intravenously at the dosage of 80 mg/kg. Groups of 5 rats were killed at 15, 30, 60 and 120 min after iv. The results showed that the peak tissue levels were obtained within 15 min, the drug disappeared from the blood very rapidly, and only 0.34 microgram/ml was found in the plasma after 120 min. The highest level was found in brain which attained about 13.9 micrograms/g wet tissue 15 min after iv injection, moderate in heart, lung and skeletal muscle, whereas the levels in liver and kidney were low. At 15, 30 and 60 min, the plasma drug concentrations were 18.5, 6.9 and 2.3 micrograms/ml, and the brain drug concentrations were 14.0, 8.8 and 3.4 micrograms/g wet tissue, respectively.