Precipitation

Intellipharm has a unique approach to modeling drug precipitation. First, a variable is created to track the amount of precipitated solid drug. The initial value of the variable will be zero, and it will have a unique solubility associated with it that is different from the solubility of the form of the drug that is dissolving from the dosage form. At each step of the numerical simulation, a line of code will compare the concentration of the dissolving drug to the solubility of the form of drug that might precipitate. Through experimentation, the concentration of the dissolving drug that will initiate the nucleation of the new drug form needs to be determined. When the degree of supersaturation is high enough to initiate nucleation, precipitation of the new form of drug will begin. The rate of precipitation will depend on the number of nuclei, their size, and whether nucleation is a one-time event or occurs over a period of time. The rate of precipitation will also depend on the ever changing concentration gradient differential and the diffusion layer thickness between the supersaturated concentration of the drug in the bulk solution and the solubility of the precipitated drug at its surface. In essence, precipitation is modeled as the reverse of dissolution. This approach to modeling precipitation will result in particles being generated that can then redissolve if conditions change in the gastrointestinal tract.