In situ experiments, such as the Doluisio method and Single-Pass Perfusion technique, provide critical insights into drug uptake by simulating in vivo conditions for drug absorption.

The Doluisio method involves perfusing a prepared segment of a rat's small intestine with a solution of radiolabeled drug and a non-absorbable marker. This helps to differentiate between absorbed and non-absorbed drug concentrations. The intestinal segment is connected at both ends using tubing and syringes, allowing the drug that passes through to be collected and analyzed. This method provides valuable information regarding the rate and extent of drug absorption.

The single-pass perfusion technique is another in situ method in which the drug solution is passed through the rat's intestinal segment only once. This technique enables steady laminar flow to precisely adjust hydrodynamic issues like flow turbulence or mixing and ensures accurate drug permeability and absorption kinetics measurement.

Both methods aid in understanding the drug's physicochemical properties, formulation factors, and patient characteristics that affect drug uptake from the gastrointestinal tract (GIT). These techniques help develop effective drug delivery systems and dosage forms. Therefore, these in situ experiments are instrumental in comprehending how drugs are absorbed within the body.