A single surface having specified physical dimensions is presented for dissolution. Compact, as used here, is a nondisintegrating mass resulting from compression of the material under test using appropriate pressure conditions. Although passing the test does not definitively demonstrate bioavailability of the sample or bioequivalence to other products, failure is a cause for concern.Dissolution Tester USP DISSOLUTION TESTING: How Does It Work Dissolution apparatus Dissolution Test Apparatus 6 Stations Dissolution Apparatus Demonstration.This general information chapter Apparent Intrinsic Dissolution≽issolution Testing Procedures for Rotating Disk and Stationary Disk 1087 discusses the determination of dissolution rates from nondisintegrating compacts exposing a fixed surface area to a given solvent medium. The dissolution test in a USP drug product monograph helps evaluate the performance of a drug product (article) and indicates when the drug product performs in a substandard fashion.

A simplifying assumption in constant surface area dissolution testing is that the pH at the surface of the dissolving compact is the same as the pH of the bulk dissolution medium. In the latter cases, the dissolution rate may depend strongly on the pH, buffer species, and buffer concentration. Dissolution properties are also influenced by extrinsic factors such as surface area, hydrodynamics, and dissolution medium properties, including solvent (typically water), presence of surfactants, temperature, fluid viscosity, pH, buffer type, and buffer strength.The medium temperature and pH must be controlled, especially when dealing with ionizable compounds and salts. The effect of impurities associated with a material can also significantly alter its dissolution properties. Among these are coprecipitates and the use of racemates and enantiomeric mixtures.

For weak acids, the pH of the dissolution medium should be one to two pH units below the pKa of the dissolving species. To assess intrinsic solubility, experimental conditions should be chosen to eliminate the effect of solute buffering, alteration of solution pH, and precipitation of other solid state forms at the surface of the compact. Under these conditions, the pH at the surface of the compact may be quite different from the bulk pH due to the self-buffering capacity of the solute. For acids and bases, the solute can alter the pH at and near the surface of the compact as it dissolves.

Downward (negative second derivative) curvature of the dissolution profile is often indicative of a transformation of the solid form of the compact at the surface or when saturation of the dissolution medium is inadvertently being approached. Possible problems include physical degradation of the compact by cracking, delaminating, or disintegration. Upward curvature (positive second derivative) of the concentration versus time data is typically indicative of a systematic experimental problem. When this occurs, only the initial linear portion of the profile is used to determine the dissolution rate.

Dissolution Test Usp