Flashcards in 1 Pharmacokinetics and 2.1 Pharmacodynamics Deck (20)
What is the Volume of Distribution?
The distance that a drug will be distributed into the tissues and fluid compartments.
It is proportional to the half life of the drug
What organs are involved in 1st Pass Drug Metabolism? How?
The Liver - CYP450 enzymes
The Gut Wall - drugs can increase efflux
The Gut Lumen - gastric acid, grapefruit juice
What 2 things affect the distribution of a drug?
Volume of Distibution
What factors can change the distribution of a drug to tissues?
Regional Blood Flow
What can displace a drug from being protein bound?
What are CYP450?
Enzymes in the liver which catalyse the metabolism of some drugs
Not all types are present in everyone, causes heterogeneity to drugs
What things inhibit CYP450?
What things induce CYP450?
St Johns Wort
Which Drugs should be monitored?
Narrow Therapeutic Window
Long Half Life
Patients with Renal, Hepatic Failure
What is multi-compartment modelling?
When we look at half life and volume of distribution we are normally assuming only one compartment.
There is a way of seeing how drugs will act in many compartments as they'll each have their own elimination rates
What is the Fluid distribution of the body?
5L in Plasma (12%)
14L in the Interstitium (33%)
23L in ICF (55%)
What is the difference between specificity and selectivity?
Specificity is how specific it is to one type of receptor
Selectivity is how selective it is to the target - side effects
How can drugs interact with another's Pharmacokinetics?
Absorb: drugs can interact with gut motility/flow rate
Distribute: displace from proteins
Metabolise: Affect CYP450
Eliminate: Protein binding, tubular secretion, pH, age
What classes of drugs have common interactions?
Which diseases can interact with drug metabolism?
How does Cardiac disease interact with metabolism?
Decreased CO so reduced organ perfusion
Increased interaction with hypotensive drugs.
Oedema leads to reduced absorption
How does Renal disease interact with metabolism?
Decreased GFR so Reduces Clearance
Nephrotoxins do further damage
How does Hepatic disease interact with metabolism?
Decreased Protein production
Decreased enzyme activity
What increases the risk of ADRs?
Drugs with Narrow TIs