Abstract

Intrinsic dissolution testing allows characterizing drug substances through its dissolution rate when exposed to a specified surface area in a specific dissolution media. This can be used to determine if a drug substance is highly or poorly soluble. In this work, DDDPlus version 4.0 (Simulations Plus, Inc.) was used to simulate intrinsic dissolution experiments for pyrimethamine and metronidazole. These drugs have low and high solubility properties. Predicted intrinsic dissolution rates (IDR) were compared to observed in vitro IDR. Physicochemical parameters from literature and the experimental conditions of the intrinsic dissolution tests for each drug were used as input data into the software. The program was able to predict the IDR of pyrimethamine and metronidazole within a pH range of 1.0 to 7.2. Observed and predicted IDR values for both drugs showed high correlations (R2 > 0.9424). The IDR values from simulations showed the pH-dependent solubility of pyrimethamine and metronidazole, allowing us to classify the solubility according to the Biopharmaceutics Classification System (BCS). Intrinsic dissolution test simulations using DDDPlus can be used to obtain a BCS solubility classification of a drug substance, helping to reduce the number of laboratory experiments.