Pharmacokinetics and Pharmacodynamics
Transport: Water-soluble drugs enter cells through channels, while lipid-soluble ones passively diffuse through any part of the cell membrane.
Most drugs are absorbed in the small intestine due to its rich blood supply and extensive villous surface, and it occurs by means of passive diffusion.
Stress and food lead to decreased gastric emptying, and hence decreased drug absorption.
Total body water (TBW): 42 liters, divided as follows:
Intracellular: 28 liters
Extracellular: 14 liters: four liters of plasma and 10 liters of interstitial fluid
Note: Drugs with a small molecular weight are distributed mainly in the interstitial fluid, while those with large molecular weight (e.g., aminoglycosides) are distributed mainly in the plasma.
Definition: It is the portion of the drug reaching the systemic circulation.
Bioavailability= Area under curve (AUC) in the oral form/Area under curve (AUC) in the...