Inverse supercritical extraction of acetaminophen from suppositories.

The use of supercritical CO2 for the isolation of acetaminophen from the non-polar matrix of a suppository is demonstrated. Since acetaminophen is not soluble in pure CO2 at low pressure, but the waxy matrix is, the later can be extracted, leaving the acetaminophen behind. After studies on acetaminophen solubility as a function of pressure, temperature flow and supercritical fluid volume, optimal extraction conditions were determined. In this method, the matrix is removed using pure CO2 at 1500 psi and 40 degrees C, and the remaining acetaminophen is then removed from the extraction cell using ultrasound in warm water. This method is an alternative to the US Pharmacopoeia's (USP) method for this kind of formulation, which involves the dissolution of the matrix in hexane with the subsequent liquid-liquid extraction of the acetaminophen into water.