Dissolution of fludrocortisone from phospholipid coprecipitates

The physical properties and dissolution behavior of phospholipid coprecipitates of fludrocortisone acetate (FA) prepared from ethyl acetate, as well as the effect of added polymer, have been determined. The fraction dissolved after 90 min and the initial dissolution rate (IDR) of coprecipitates containing dimyristoyl phosphatidylcholine (DMPC) (4:1, w/w; FA:DMPC) were 77% and 3.5-fold greater than for FA at pH 2.0 and 37 degrees C. The mechanisms of dissolution were similar to those previously established for griseofulvin, but no aging occurred over 4 months at room temperature in a desiccator. The addition of 0.01 mol% of dextran (MW = 2 million) or 0.1 mol% of poly(lactic acid) reduced the fraction of FA dissolved in 90 min by 15% and reduced the IDR by 35%. The addition of poly(vinylpyrrolidone) (PVP) resulted in a minimum of dissolution efficiency at 1 mol% of PVP 10 (MW = 10,000) or PVP 24 (MW = 24,000) and at 0.1 mol% PVP 40 (MW = 40,000). Only PVP 24 influenced the melting point and heat of fusion of the coprecipitates (determined by differential thermal analysis). Coprecipitate dissolution was reasonably described by either second-order or Weibull distribution kinetic models. These results support the application of high drug-containing solid dispersions using phospholipids to increase the dissolution behavior of poorly water-soluble drug solvates and the possibility of modifying drug release by the incorporation of small amounts of polymers.