Where are oral medications predominantly absorbed and why?

Oral medications are predominantly absorbed in the small intestine primarily because of the larger surface area it offers. The small intestine has numerous folds, villi, and microvilli, which greatly enhance its absorptive capacity compared to other parts of the gastrointestinal tract. This increased surface area allows for a higher rate of absorption of medications.

Furthermore, the environment in the small intestine is conducive to the absorption of many drugs. Most oral medications are better solubilized and have improved absorption in the slightly alkaline pH of the small intestine compared to the more acidic environment of the stomach. The small intestine also has a rich supply of blood vessels that facilitate the rapid transfer of absorbed medications into the bloodstream, ensuring they can quickly exert their therapeutic effects.

The other areas mentioned, like the stomach and colon, are less favorable for absorption. The stomach’s high acidity can hinder the solubility of some drugs, while the colon’s slow motility may delay absorption and limit the extent of drug uptake. Absorption in the lungs is typically associated with inhaled medications, which is not relevant for oral medications. Thus, the small intestine’s anatomical and physiological characteristics make it the primary site of oral drug absorption.