Pharmacokinetics Lecture 2 Flashcards
Pharmacokinetics phase
The study of the movement of drugs into, within and out of the body that is necessary to achieve drug action
Phases
Absorption
Distribution
Metabolism
Excretion
Absorption
Movement of drugs into the bloodstream after administration
Pharmaceutic phase
When a drug is in solid form and disintegrates into smaller particles and combine with liquid form a solution
Excipients
Fillers and inert substances
What environments so drugs disintegrate and absorb faster in?
Acidic fluids with a pH of 1 or 2 rather than alkaline fluids
Small intestines form
Covered with villi which increase the surface area available for absorption
Enteric coated drugs disintegrate where?
Resist disintegration in gastric acid of the stomach
Only occurs until drug reaches alkaline environment in small intestine
Passive absorption
Diffusion
Active absorption
Requires carrier (enzyme) and energy is required
Pinocytosis
Cells carry drag across membrane by engulfing particles
What is the GI membrane composed of
Mostly lipid (fat) and protein (Drugs that are lipid soluble pass rapidly through)
What needs a carrier to pass through the membrane?
Water soluble drugs need an enzyme or protein and can’t cross blood brain barrier
How do large particles pass through cell membrane?
Nonionized
What drugs absorb the fastest
Drugs that are lipid soluble and nonionized
Where do drugs absorb faster?
Drugs given IM= more more blood vessels
Where do drugs absorb slower
Subcutaneous tissue because there is fewer blood vessels
First pass effect
Some drugs don’t got to systemic circulation but pay to the intestinal lumen to the liver
What happens in the liver?
Some drugs me metabolize in inactive form than excreted (reducing amount Of active drug)
Bioavailability
% of drug available for use
PO<100%
IV=100%
Desired drug effect= oral does is 3-5x larger than dose for IV
Factors effecting bioavailability
Drug form Route GI mucosa and motility Presence of food and other drugs Changes in liver metabolism or function
Effect rapid absorption on bioavailability
Increased bioavailability and can increase drug concentration which Amy lead to drug toxicity
Effect of Slow absorption on bioavailability
Limit the bioavailability of drug causing decrease drug concentration
Distribution
Process by which drug becomes available to the body fluids and tissues
