Integration of Precipitation Kinetics From an In vitro, Multicompartment Transfer System and Mechanistic Oral Absorption Modeling for Pharmacokinetic Prediction of Weakly Basic Drugs
Solubility, dissolution, and precipitation in the gastrointestinal tract can be critical for the oral bioavailability of weakly basic drugs. To understand the dissolution/precipitation during the transfer out of the stomach into the intestine, a multicompartment transfer system was developed by modifying a conventional dissolution system. This transfer system included gastric, intestinal, sink/supersaturation, and reservoir compartments. Simulated gastric fluid (SGF) and fasted state simulated intestinal fluid (FaSSIF) were used in the gastric and intestinal compartment respectively to mimic fasted condition. The new transfer system was evaluated based on two model weak bases, dipyridamole and ketoconazole. Traditional two stage dissolution using 250 mL of SGF media, followed by 250 mL of FaSSIF, was used as a reference methodology to compare dissolution/precipitation results. An in silico model was built using R software suite to simulate the in vitro time-dependent dissolution and precipitation process when formulations were tested using the transfer system. The precipitation rate estimated from the in vitro data was then used as the input for absorption and pharmacokinetic predictions using GastroPlus. The resultant simulated plasma concentration profiles were generally in good agreement with the observed clinical data, supporting the translatability of the transfer system in vitro precipitation kinetics to in vivo.