W3- Lecture 15.1- Pharmacokinetics

Question 1

Name 6 important properties for a clinically useful drug

Answer 1

Stable form amenable to introduction into the body
Pass into the body
Reach its biological target
Remain in the body long enough to achieve its therapeutic end
Not produce harm while in the body
Exit the body when it’s job is done

Question 2

Define Pharmacodynamic effects

Answer 2

what drug does to body

Question 3

Define Pharmacokinetic effects

Answer 3

what body does to drug

Question 4

Absorption, distribution, metabolism & excretion (ADME) depend on:

Answer 4

Route of administration of drug
Physico-chemical properties of drug
Physiological variables
These can differ greatly between individuals e.g. age, health condition, size, gender, race.

Question 5

Describe absorption after oral intake

Answer 5

Mainly absorbs in small intestine

Some in large intestine

Question 6

What is bioavailability ?

Answer 6

The ability of drug to be where it is needed

Question 7

What is bioavailability of a drug taken orally determined by ?

Answer 7

Efficiency of absorbion

Presentation in the blood

Question 8

Which factors may effect how fast a drug is absorbed into the GI track ?

Answer 8

Surface area of a membrane/organ 
Ph of site 
Mesenteric blood flow
(also blood flow increased after a meal  )
Gastric Emptying 
Presence of food 
No. Of efflux transporters in membranes 
Formulation of drug
Physio chemicals of drug 

Biological differences
Health, size,weight , diet, age , gender , ethnicity

Question 9

What three factors effects diffusion through cell membranes ?

Answer 9

Conc grad

Presence of carrier proteins/ efflux pumps

Permeability coefficient P 
Which depends on 
Lipophilicity (hydrophobicity) of the drug
Ionisation state(dependant on ph )
Size
Diffusibility of the drug molecules

Question 10

Describe distribution in terms of compartments

Answer 10

If we look at the body as a volume of water split into 3 compartments
Blood , 5L
extracellular fluid 15L
and intracellular25L

Question 11

What does distribution between different compartments depend on ?

Answer 11

Molecular size
Ability to cross membranes
And extent of binding to plasma membrane

Question 12

Which compartments is warfarin mainly found ?

Answer 12

In blood

Question 13

Where is Tubocurarine (neuromuscular blocker) highly ionized found ?

Answer 13

Extracellular fluid

Question 14

Where can you find Ethanol, diazepam, morphine, paracetamol ?

Answer 14

All highly soluble

Distributed in total body water

Question 15

Describe bioavailability of a drug in terms plasma protein binding

Answer 15

Loose electrostatic bonding for
Acidic drugs- albumin
Basic drugs- glycoprotein

Some drugs 90-99% such as NSAIDS and warfarin
Equilibrium established between bound and free form this reduces free drug conc available in plasma to reach site of action

Question 16

Describe the potential risk of warfarin

Answer 16

As warfarin has a narrow therapeutic window - risk of internal bleeding or blood clots (too low)
Bioavaliabily of warfarin only 1%in the blood not bound to serum albumin
+ other drugs compete for the same

This means that if ther are changed to the albumin sites for warfarin then bioavailability of w will change massively
So be use of this warfarin needs regular therapeutic monitoring