a mass-balance determination or in comparison to an intravenous dose. For dissolution class boundaries, an immediate release product is considered rapidly dissolving when no less than 85% of the labeled amount of the drug substance dissolves within 15 minutes using USP Dissolution Apparatus 1 at 100 RPM or Apparatus 2 at 50 RPM in a volume of 900 ml or less in the following media: 0.1 M HCl or simulated gastric fluid or pH 4.5 buffer and pH 6.8 buffer or simulated intestinal fluid. See also ADME Partition coefficient Bioavailability Drug metabolism First pass effect Polar surface area IVIVC References Further reading External links BCS guidance of the U.S. Food and Drug Administration Pharmacological classification systems Pharmacy in the United States