Pharmacokinetics Flashcards
(21 cards)
Most drugs are absorbed by this route due to its convenience.
Oral
This directly enters the blood stream bypassing absorption barriers
Intravenous
Drugs in aqueous solutions that are rapidly absorbed
IM, SC
What is half life?
The time taken for the concentration of a drug in blood stream to fall by 50%
What is volume distribution?
The volume into which the drug is distributed.
[<5L = drug in vascular compartment]
[<15L = drug in extracellular fluid]
[>15L = drug distributed through total body water or tissue]
What is clearance?
The volume of blood or plasma cleared of a drug in unit of time
What is bioavailability?
The proportion of drug reaching systemic circulation
Which form of excretion is responsible for the elimination of most drugs?
Renal excretion
What helps reduce lipid soluble compound?
Metabolism
If drug is too lipid soluble, what happens?
It is reabsorbed in the renal tubules
Biliary excretion is?
excretion of drugs into bile and then into the small intestine
What happens during metabolism?
1) Drug is made more hydrophilic to ease excretion through kidneys.
2) Metabolites are less active than parent drug
What is inactive until metabolised in the body to active drug?
Prodrugs
Phase I reactions are…
the biotransformation of a drug to a more polar metabolite
Oxidations are…
the most common reactions in Phase 1.
Catalysed by a class of enzymes called cytochrome P450’s
Phase 2 reactions are..
when a drug that is not sufficiently polar are made more hydrophilic by conjunction with endogenous compound in the liver
What drugs are bound to plasma proteins?
Lipophilic drugs
What is first pass metabolism?
When an oral drug is given and absorbed in the small intestine, it enters the portal system to travel to the liver to be metabolised.
What are Cytochrome P450’s
A type of enzyme forming a superfamily of related enzymes that differ in amino acid sequence.
What does phase 2 reaction involve?
Conjugation of a drug or its phase 1 metabolite with an endogenous substance
