USE OF SUPERCRITICAL-FLUID EXTRACTION FOR SAMPLE PREPARATION OF SUSTAINED-RELEASE FELODIPINE TABLETS

Supercritical fluid extraction (SFE) was shown to be an accurate and p recise alternative to liquid extraction for sample preparation of sust ained-release felodipine tablets (5 mg potency) while realizing an 80% reduction in solvent consumption. Extractions of felodipine spiked on an inert support were used to evaluate the solubility of felodipine i n CO2 as well as analyte trapping after SFE. Even though the pure drug was found to be soluble in pure CO2, extractions of felodipine from t he tablet matrix required moderate modifier concentrations [8.7% (v/v) methanol in CO2] in order to overcome strong matrix-drug interactions . Sequential static/dynamic extraction steps were also required to qua ntitatively recover the drug from the tablet matrix, indicating that t he drug extraction was diffusion-limited. Average recoveries (n = 5) f or the optimized SFE method were determined to be 4.93 mg felodipine/t ablet (98.6% claim) with an RSD of 1.2% versus those for the liquid ex traction procedure (n = 5, 4.98 mg/tablet, 99.6% claim, 2.4% RSD). Sim ilar levels of drug degradation (0.12% expressed as felodipine) were a lso obtained with both the traditional liquid extraction and with the SFE method.