Pharmacology exam

Question 1

What is pharmacokinetics?

Answer 1

The effect that the processes of the body have on a drug - how the drug moves through the body

Question 2

What is pharmacodynamics?

Answer 2

The effect that a drug has on the processes of the body - The response the body has to the drug

Question 3

The 4 processes involved in pharmacokinetics

Answer 3

Absorption, distribution, metabolism, excretion

Question 4

Define Absorption

Answer 4

Absorption - how the drug crosses a biological membrane and enters the circulation (none if given IV)

Question 5

Define Distribution

Answer 5

Distribution - how the drug is transported by the circulation around the body

Question 6

Define metabolism

Answer 6

Metabolism - how the drug is inactivated or transfomed by enzyme action.
Usually metabolites are produced which are more water soluble so can be excreted

Question 7

Define Excretion

Answer 7

How the drug is removed from the body

Question 8

Steps a prescriber can use to minimise ADR’s

Answer 8

Avoid giving medication unless you have to
Check previous reactions/allergies
Assess other medications including OTC and herbal
Be aware of age, renal function and hepatic disease
Prescribe as few drugs as possible
Give clear indications for administration
Consider if exipients could cause reaction

Question 9

Factors that affect a patients ability to metabolise drugs

Answer 9

Liver funtion and disease
Genetics - ie codeine metabilism
Age - delayed production and elimination of metabolites may prolong drug action
Reduced hepatic blood flow
Tolerance - if drugs have been given repeatedly.

Question 10

Name sites of drug excretion

Answer 10

KIDNEYS - most drugs and metabolites are excreted here
Bile - excreted from liver to bile and eventually faeces
Lungs - Alcohol and anaesthetics
Breast milk
Sweat
Saliva
Tears

Question 11

What factors do you need to consider when prescribing for an elderly patient?

Answer 11

Do they take other medicines?
Can they take the medicine - remember/ open container/ swallow / read instructions etc
Decreased renal function - may affect elimination
Size/weight
Decreased gastric emptying - so reduced absorbption of oral drugs
Decreased plasma proteins

Question 12

Define steady state…

Answer 12

The point at which the rate of ELIMINATION (not excretion) of an orally administered drug is equal to its rate of absorption

Question 13

Define volume of distribution

Answer 13

The (theoretical) amount of drug in the body (dose) to the concentration that is measured (in blood, plasma etc)

Question 14

What is an agonist

Answer 14

b) a drug which binds to a receptor and elicits an effect

Question 15

What is an antagonist?

Answer 15

A drug that blocks or dampens a biological response by binding to and BLOCKING a receptor

Question 16

What is therapeutic drug monitoring?

Answer 16

When regular plasma blood levels are taken - ie to ensure drugs with a narrow theraputic index are used effectively

Question 17

Define therapeutic index

Answer 17

Its the range between the toxic dose and the amount of drug required to have a theraputic effect.

Question 18

Define the purpose of metabolism on a drug…

Answer 18

Modifying the chemical composition of the drug, usually to remove the pharmacological activity of the drug. Metabolites are usually more water soluble then the drug which promotes excretion from the body. Most metabolism occurs in the liver by hepatic enzymes. Metabolic processes include oxidation, reduction, hydrolysis and conjugation. Metabolism can also make a drug active - ie codiene to morphine

Question 19

What factors can affect oral absorption of a drug?

Answer 19

Gut motility - less absorbed if increased
gastric emptying - speeds up absorption
gut ph
blood flow
presence of food and fluid
antacids
drug composition - liquid preparations nore readily absorbed then solids
Lipid solubility

Question 20

What is meant by bioavailability?

Answer 20

the fraction of an administered dose which reaches the general systemic circulation in an unbound / unaltered form and is able to exert its mode of action.

Question 21

How could bioavailability of a drug be increased or decreased?

Answer 21

Increased metabolism at first pass
Decreased absorption from site of action
Protein binding in plasma
Distribution into other body tissues
Intravenous route

Question 22

Define loading dose…

Answer 22

A dose which is larger than normal to allow the plasma steady state to be reached quickly

Question 23

What does half-life mean?

Answer 23

It’s the time taken for the concentration of the drug ion the blood to fall by half its original value - used to allow a dose to be calculated to produce a stable plasma concentration

Question 24

What is an adverse drug reaction?

Answer 24

An unwanted or unintended effect of a medicine which occurs during proper use at a normal dose

Question 25

What is first pass metabolism?

Answer 25

When a drug gets absorbed from the GI tract, and travels to the liver via the portal vein and gets metabolised there resulting in loss of active drug to continue to the general circulation and reduced bioavailability.

Question 26

Which ONE of the following is a true statement ?

a) A drug which binds readily to plasma proteins must be given by the I.V route
b) A drug which binds readily to plasma proteins is known as an agonist
c) A drug which binds readily to plasma proteins may be displaced by another drug competing for binding sites
d) A drug which binds readily to plasma proteins cannot be absorbed from the GI tract

Answer 26

c) A drug which binds readily to plasma proteins may be displaced by another drug competing for binding sites

So… the drug has entered the blood stream but become bound to the protein (like riding in a taxi) so in general are not active (when bound they are too big to pass through cell membranes). Warfarin in 98% plasma bound - so only 2% active however if asprin comes along it may displace some (like fighting for a taxi) and therefore there will be more UNBOUND warfarin in the circulation - more active drug.

Question 27

Give an example of a pharmacokinetic drug interaction

Answer 27

So an interaction involving how the processes of the body effect the drug - ie absorption, distrobution, metabolism, excretion.
Warfarin binds to plasma proteins. Asprin may knock it off these hence increasing the active amount in the blood stream.

Question 28

Give an example of a pharmacodynamic drug interaction

Answer 28

So an interaction that involves how the drug affects the processes of the body
ie drugs which could cancel each other out or reduce effects
ACE inhibitors and NSAIDS

Question 29

Which symbol is used in the BNF to identify a drug where there has been limited use and the MHRA require that all suspected adverse reactions are reported

Answer 29

A Black triangle

Question 30

Briefly explain the purpose of metabolism of a drug

Answer 30

To change an administered drug into its active form
To change an active drug into an inactive or less active compound
To change a drug into a more water soluble form to allow it to be excreted by the kidney.

Question 31

What do you understand by the term “steady state” and how might this inform your prescribing?

Answer 31

This is the term used to describe the point when, after repeated doses of a drug , the rate of absorption is equal to the rate of elimination
The plasma level at this point remains constant within a particular range
This can be used to determine the optimal dose for therapeutic effect and minimal side effects
For drugs with a long half life a loading dose may be needed to achieve this therapeutic range within a suitable time frame.

Question 32

Whats the difference between elimination and excretion?

Answer 32

Excretion is the irreversable removal of the drug from the body ie via kidneys, sweat, etc. Elimination is the metabolism of the drug to an inactive state which may then be excreted

Question 33

List factors which may be important to consider when prescribing for a child

Answer 33

Can they take the preparation?
Is it liscenced for use with children
Weight
Age
Is the dosing schedule appropriate