1 Pharmacokinetics and 2.1 Pharmacodynamics

Question 1

What is the Volume of Distribution?

Answer 1

The distance that a drug will be distributed into the tissues and fluid compartments.
It is proportional to the half life of the drug

Question 2

What organs are involved in 1st Pass Drug Metabolism? How?

Answer 2

The Liver - CYP450 enzymes
The Gut Wall - drugs can increase efflux
The Gut Lumen - gastric acid, grapefruit juice

Question 3

What 2 things affect the distribution of a drug?

Answer 3

Protein Binding

Volume of Distibution

Question 4

What factors can change the distribution of a drug to tissues?

Answer 4

Regional Blood Flow
Disease States
Drug Interactions
Lipid Solubility
Receptor Types
Active Transport

Question 5

What can displace a drug from being protein bound?

Answer 5

Pregnancy
Low Albumin
Other Drugs
Renal Failure

Question 6

What are CYP450?

Answer 6

Enzymes in the liver which catalyse the metabolism of some drugs
Not all types are present in everyone, causes heterogeneity to drugs

Question 7

What things inhibit CYP450?

Answer 7

Sulphonamide
Grapefruit Juice
Cranberry Juice
Omeperazol
Isoniazide

Question 8

What things induce CYP450?

Answer 8

St Johns Wort
Alcohol
Rifampicin 
Pheyltoin
Barbituates

Question 9

Which Drugs should be monitored?

Answer 9

Narrow Therapeutic Window
Long Half Life
Patients with Renal, Hepatic Failure

Question 10

What is multi-compartment modelling?

Answer 10

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

Question 11

What is the Fluid distribution of the body?

Answer 11

5L in Plasma (12%)
14L in the Interstitium (33%)
23L in ICF (55%)

Question 12

What is the difference between specificity and selectivity?

Answer 12

Specificity is how specific it is to one type of receptor

Selectivity is how selective it is to the target - side effects

Question 13

How can drugs interact with another’s Pharmacokinetics?

ADME

Answer 13

Absorb: drugs can interact with gut motility/flow rate
Distribute: displace from proteins
Metabolise: Affect CYP450
Eliminate: Protein binding, tubular secretion, pH, age

Question 14

What classes of drugs have common interactions?

Answer 14

Antidepressants
Anticonvulsants
Antibiotics
Antiarrhythmic 
Anticoagulants

Question 15

Which diseases can interact with drug metabolism?

Answer 15

Renal
Hepatic
Cardiac

Question 16

How does Cardiac disease interact with metabolism?

Answer 16

Decreased CO so reduced organ perfusion
Increased interaction with hypotensive drugs.
Oedema leads to reduced absorption

Question 17

How does Renal disease interact with metabolism?

Answer 17

Decreased GFR so Reduces Clearance
Electrolyte disturbances
Nephrotoxins do further damage

Question 18

How does Hepatic disease interact with metabolism?

Answer 18

Decreased Protein production

Decreased enzyme activity

Question 19

What increases the risk of ADRs?

Answer 19

Age
Co-morbidities
Polypharmy
Ignorant Prescribing
Drugs with Narrow TIs

Question 20

What causes heterogeneity with responses to drugs?

Answer 20

Genetic Factors - Enzymes
Age
Sex 
Weight
Dose, Route, Administration 
General Health 
Other Drugs