Drug Absorption: Mechanisms and Factors

A set of vocabulary flashcards defining transport mechanisms and factors that influence drug absorption.

Transcellular Transport

An intracellular transport mechanism involving permeation through the GI lipoidal barrier, the intracellular space (cytosol), and the basolateral membrane.

Passive Transport Processes

Processes driven by Brownian motion that require no energy, including passive diffusion, ion-pair transport, and facilitated diffusion.

Active Transport Processes

Transport processes that require energy from ATP, consisting of primary active transport and secondary active transport (symport and antiport).

Vesicular Transport

An energy-dependent transport mechanism (endocytosis) across the cell membrane via vesicles, including pinocytosis and phagocytosis.

Aqueous Solubility

A factor affecting absorption requiring drugs to be in solution to be absorbed (e.g., tablets must disintegrate first).

Formulation

The preparation of a drug containing inert substances (such as lactose, starch, and calcium) that affect absorption.

Lipid Solubility

A drug property enabling faster absorption because biological membranes are lipid (e.g., acyclovir).

Surface Area

An anatomical factor where a greater area leads to rapid absorption, as exemplified by the small intestine with villi.

Motility of GIT

Gastrointestinal movement where a slight increase favors drug absorption by contact.

Ionization of Drugs

A physicochemical factor based on the fact that most drugs are weak electrolytes and their ionization is pH-dependent.