The concept of dissolution efficiency

The recent interest in drug availability has resulted in a proliferation of in vitro dissolution testing, now standard for many dosage forms. The usual method of evaluation is the comparison of the time taken for given proportions of the active drug to be released into solution and figures such as the t20, t50 and t90 % times are often quoted. Alternatively the fraction of drug in solution after a given time is used for comparison, i.e. 60% release in 30 min. A further parameter suitable for the evaluation of in vitro dissolution has been suggested by Khan & Rhodes (1972), who introduced the idea of Dissolution Efficiency. This is defined as the area under the dissolution curve up to a certain time, t, expressed as a percentage of the area of the rectangle described by 100% dissolutionin the sametime. The simplest case, shown in Fig. 1 where, dissolution of a tableted drug, is