Evaluation of floating and sticking extended release delivery systems: an unconventional dissolution test

The extent to which hydrophilic matrix tablets with a propensity to stick to the dissolution apparatus and/or float are susceptible to variations in hydrodynamic conditions during dissolution testing was investigated. Furthermore the usefulness of simple alternatives to the current compendial tests is examined. Swellable hydrocolloid (guar) matrix tablets containing verapamil HCl were evaluated using USP dissolution apparatus I and II. Two additional configurations where an additional single ring and mesh device or a double mesh device was located below the paddle in the dissolution vessel were also evaluated. Tablets were placed on top of the single mesh device or in the compartment formed by the two mesh surfaces of the double mesh device. In all cases near linear (n>/=0.82) release profiles were observed. When using apparatus I it was observed that the highly swellable tablets were fully constricted by the basket within 5-7 h. This prevented further independent movement and unimpeded swelling and coincided with a departure from linear release and increased variability (S.D.