DISSOLUTION RATES OF SPARINGLY SOLUBLE TABLETS

The automated dialysis method offers an opportunity for the accurate evaluation of the dissolution rates of sparingly soluble dosage forms. By the analysis of kinetic models, the dissolution rates for disintegrating and non‐disintegrating dosage forms may be calculated. The theory is used to examine the effect of additives and compression force on the dissolution rates of sulphathiazole tablets. At the fairly low compression forces used (640–1430 kg) the dissolution rate gradually increases due to penetration of the tablet by the dissolution medium. Polyethylene oxide causes an initial rapid increase in dissolution rate, but the formation of a mucilaginous film results in a constant rate. Using starch, dissolution rate increases rapidly as a result of tablet disintegration. This disintegration is shown to make available less than half the surface area of the original powder. The dissolution rate constant for sulphathiazole under the experimental conditions is 2–75 × 10−4 cm min−1. 1969 Royal Pharmaceutical Society of Great Britain