Specificity of the Relationship between Rate of Dissolution and Disintegration Time of Compressed Tablets

Dissolution rates and disintegration times of 76 lots of tablets were determined employing the U.S.P. disintegration apparatus without plastic disks. The time for 50% of the drug to dissolve (t50%) or the amount of drug in solution at a specific time was used as criteria of the rate of dissolution. Disintegration times were also obtained with plastic disks. The drugs included a steroid, a sulfonamide, an antidiabetic agent, and an aspirin-phenacetin-caffeine combination. In some cases there was a quantitative relationship between t50% and one or both of the disintegration times. In other cases there was none. Where a quantitative relationship existed, the slopes of the lines relating the variables varied widely and depended upon the drug(s) involved, and in one case upon the presence of a pharmaceutical adjuvant. With two of the series of tablets, one could not differentiate between lots on the basis of their disintegration times determined with plastic disks. However, in one of these series disintegration times were determined without plastic disks, and in both the t 50% values clearly identified lot-to-lot variation. Questions are raised regarding the use of plastic disks in the official disintegration test and the validity of applying uniform disintegration standards to large groups of drugs in tablets. An explanation for the correlation between in vivo availability of certain drugs administered as tablets to human subjects and their disintegration times is presented.