The journey of drugs within the human body involves several stages and mechanisms that determine their efficacy and behavior. Initially, drugs taken orally are absorbed through the gastrointestinal tract, involving the stomach lining and small intestine, before reaching the liver.
most of the work in cells and are required for the structure, function, and regulation of the body’s tissues and organs.
Proteins are large, complex molecules that play many critical roles in the body
it binds to the target receptor site, they can either block the physiological function of the protein, or mimics it's effect
liver
metabolizing drugs is via a specific group of cytochrome P-450 enzymes
once in liver enzymes convert prodrugs to active metabolites or convert active drugs to inactive forms
when drugs are taken orally they pass through the gastrointestinal tract, absorbed by stomach acid and then finally reach the liver
fat
The distribution of a drug between fat and lean tissues may influence its pharmacokinetics
Increased volume of distribution for lipid-soluble drugs
enzymes
molecules have a specific three-dimensional structure which allows only substances that fit precisely to attach to it.
compete for binding with enzymes substrate
The majority of drugs which act on enzymes act as inhibitors and most of these are competitive
receptors
the binding can be specific and reversible. a ligand may activate or inactive a receptor; activation may increase or decrease particular cell function
molecules that bind to a receptor are called ligands
those molecules than bind to receptors on the cell, activating the receptor and generating a biochemical or electric signal inside the cell
the body receives chemical information from molecules such as drugs and hormones- outside the cell
small intestine
third being active transport of larger molecules by transport proteins
second being passive transfusion by hydrophilic drugs through pores and gap junctions
three ways drugs go through; first being passive transfusion by lipophilic drugs through the membrane.
cells
the mechanism of transport of drugs can be divided into two types; simple diffusion and carrier-medicated transport
directly crossing plasma membrane
stomach and stomach acid
the pill gets absorbed into the stomach lining and acid breaks it down in the gastrointestinal tract
Circulatory system
on skin with a patch, it can be absorb into the skin
orally take a pill
it diffuses into capillaries in the stomach and small intestine that connect to blood vessels that go directly to the liver. remnants travel to small intestine where finish dissolving.
-injection directly into the vein
first it passes throughout the body through the veins. depending on actual route. it enters venous system and gets returned to heart with deoxygenated blood before travelling to lung and back to the heart.
