In vitro experiments are crucial for understanding the transport and absorption of drugs through biological materials. These studies employ varied methods such as the diffusion cell method, the everted sac technique, and the everted ring technique.

The diffusion cell method uses a two-compartment cell, including a donor compartment with the drug solution, which simulates the environment where the drug is applied, and a receptor compartment with a buffer solution, which simulates the environment where the drug is absorbed. The technique measures the rate at which the drug arrives in the receptor compartment, providing insights into drug absorption rates.

The everted sac technique involves the eversion of a small intestine segment filled with buffer solution and immersed in a drug solution. This technique helps mimic the in vivo conditions of drug absorption in the small intestine. It leads to the drug's transport through the intestinal wall into the side opposite the lumen. The concentration of the drug in the serosal liquid is measured at predetermined intervals, offering an understanding of how drugs interact with intestinal tissues.

The everted ring technique is useful for examining specific segments of the intestine. It involves dissecting inverted sections of the intestine into rings, incubating them in a drug solution, and analyzing them for drug content. This method helps study localized drug absorption within intestinal tissues.

Additionally, cell cultures like Caco-2 cells, which model the intestinal barrier are used. Positioned on a collagen-treated synthetic polycarbonate membrane and exposed to a drug solution, these cells help understand factors influencing drug uptake. Each method offers unique insights into how drugs interact with different biological interfaces, contributing to our understanding of drug absorption processes.