Drug Distribution Flashcards
For a drug to be active it must______
Leave the circulation and enter the inter or intracellular spaces
Plasma Protein Binding
The degree to which medications attach to proteins within the blood
Less bound drug is ______
More efficiently able to diffuse into cell membranes
Blood proteins that bind to drugs
Serum albumin, lipoprotein, glycoproteins and alpha, beta and gamma globulins
An increase in unbound drugs _______in toxicity
Increases
Only unbound drugs are_______
Biologically active
The binding of drugs to proteins in the blood is ______
Reversible
Tissue Perfusion
Passage of fluids from the circulatory system or lymphatic system to an organ or tissue
Lipid soluble drugs enter_____
Highly perfused tissues such as lungs, kidney, liver, heart and brain
What happens if a lipid soluble drug is given to a person with more adipose tissue
The drug is stored in the fat and acts as a reservoir of the drug
Volume of Distribution
the degree to which a drug is distributed in body tissue rather than the plasma
Low Volume of Distribution
Drug stays in vasculature and does not enter tissues
High Volume of Distribution
Lipid soluble drugs will enter brain, liver
What is the VOD for 1g of drug
1000mg/8L = 125 mg/L
Metabolism of drug
Hepatic
Removal of drug
Renal
What is clearance of a drug measured in
ml/min
In renal what is clearance dependent on
Urine flow and concentration
In hepatic what is clearance dependent on
Bilary excretion and metabolism
Half-life
Amount of time a drugs plasma concentration drops from maximum to half
Half-life duration
4 hours
What does the half-life depend on
VOD and clearance
An increase in half-life
Increases plasma concentration
Increases toxicity
Decrease in clearance
Increase in VOD
Steady State Concentration
Overall intake of a drug is fairly in a dynamic equilibrium with its elmination
Drug elmination
The removal of active drug and metabolites from the body
Drug elimination is made up of 2 parts
Drug metabolism
Drug Excretion
Excretion is carried out by ________
Kidneys
What is the process of excretion
Glomerular filtration
Passive tubular reabsorption
Active tubular secretion
What does bilary secretion lead to
Conjugation of drug
What is conjugation
a reaction that couples the drug or its metabolites to another molecule to increase its solubility in the bile
Enterohepatic Circulation
Metabolised in liver, excreted into the bile passed to the intestinal lumen and returned to the liver via the hepatic portal vein.
Drugs that undergo Enterohepatic Circulation
Methadone Morphine Amphetamine Metronidazle Estradiol
Glomerular Filtration
All unbound drugs filtered into the glomerulus
Passive tubular reabsorption
allows drug to move back into circulation and occurs at distal tube and collecting duct
Active tubular secretion
Some drugs are actively secreted into the proximal tube
