Pharmacology exam

Question 1

What is pharmacokinetics

Answer 1

What the body does to a drug

Question 2

What are the stages of drug action

Answer 2

ADME

Absorption
Distribution
Metabolism (not all drugs are metabolised)
Excretion

Question 3

List factors that affect Absorption

Answer 3

Contact time
Surface area
Blood flow

Question 4

Particles move from high concentration to low concentration

Answer 4

Diffusion

Question 5

What are the two types of absorption

Answer 5

Physiological

Physio-chemical

Question 6

Physico-chemical factors affecting absorption

Answer 6

SLIC

Solubility- how soluble the drug is in the body fluids

Lipid to Water Partition Coefficient - is it more fat soluble than water soluble

Ionisation - degree of chemical charge

Chemical Stability - will it break down readily

Question 7

Distribution into body fluids are mainly

Answer 7

Extra cellular
Intracellular
Plasma

Question 8

Uptake of drugs into different body tissues depends on

Answer 8

Blood flow
Tissue mass
Lipid to Water Partition Coefficient

Question 9

Time to onset

Answer 9

The time it takes for a drug to reach its site of action at a concentration necessary for it to work

Question 10

Duration of effect

Answer 10

The time interval where the concentration of a drug at the site of action is above its therapeutic concentration - may be prolonged in the elderly or people with poor liver or kidney function

Question 11

Half life

Answer 11

The time it takes for the peak concentration of a drug in the plasma to reduce by half

Question 12

First pass metabolism

Answer 12

When a drug is completely destroyed in the stomach before being absorbed or when it is metabolised by the liver before reaching the systemic circulation

Question 13

Clearance

Answer 13

A measurement of a persons ability to metabolise and excrete a drug or how quickly a drug is cleared from the blood - affected by renal function, blood pressure, and urine PH

Question 14

Key principles of pharmacodynamics =

The four drug body actions are

Answer 14

RITE
Receptor = agonist and antagonist

Ion Channel = blockers and modulators

Transport system interactions

Enzyme= inhibitor, false substrate and pro-drug

Question 15

What are receptors

Answer 15

Sensing element in a system of chemical communication that coordinates the function of all the different cells in the body

Question 16

Name the four main types of receptors

Answer 16

Ligand gated ion Chanel
G -proline receptor
Kinase-linked receptor
Nuclear Receptors

Question 17

What is a Ligand

Answer 17

A chemical or drug that binds to a receptor

Question 18

What is a G- protien

Answer 18

G- proteins are found within the cell, are linked to the receptor and activate after drug molecule binding

Question 19

How does a kinase linked receptor work

Answer 19

Kinase linked receptors produce a cascade of events after drug binding that lead to an action

Question 20

What is a nuclear receptor

Answer 20

Nuclear receptors are located WITHIN the cell nucleus and require the drug molecule to cross the nuclear membrane

Question 21

Explain G - protein receptors

Answer 21

Use proteins to link to receptors in the cell membrane
EG. Salbutamol acts on
Adrenoseptors and histamine receptors in the bronchioles

Question 22

Give an example of a drug that exerts its effect using kinase linked receptor

Answer 22

insulin

Question 23

Give an example of a drug that exerts its effect via nuclear receptor

Answer 23

Levothyroxine and prednisolone

Question 24

What is an agonist

Answer 24

A drug that binds to a receptor and causes a response

Eg; many hormones neurotransmitters and drugs act as agonists - such as ventolin a beta 2 agonist activates beta cells that relax the smooth muscle of airways in the treatment of asthma

Question 25

What is an antagonist

Answer 25

A drug that binds to a target receptor and effects no response or blocks a response they bind to the same site that an agonist usually occupies thereby preventing an action

Question 26

State the two classifications of adverse drug reaction

Answer 26

Type A - augmented and Type B- Bizarre

Question 27

List four strategies used by a NMP to reduce the likelihood of ADRs

Answer 27

Prescribe as few drugs as possible Prescribe known or familiar drugs Reduce polypharmacy if possible by regular medication review Check for allergies an previous ADRs Prescribe only if there is good indication Simplify drug regimens or arrange to fit in with patients current medication times Regular reviews to monitor drug response/side effects

Question 28

Discuss your understanding of concordance

Answer 28

Factors affecting pt concordance BNF p1 Purpose of medication not clear Perceived lack of efficacy Real or perceived adverse effects Instructions for administration not clear Physical difficulty in taking the medicines eg swallowing tablets, handling small tablets, opening containers Unattractive formulations eg unpleasant taste or route Complicated regime

Question 29

Give example of a drug that undergoes extensive fist pass metabolism and the implication for route of administration

Answer 29

Insulin if given orally would be metabolised in the GI or liver and therefore greater bioavailability is achieved by subcutaneous route

Question 30

Define drug interactions

Answer 30

A pharmacokinetic drug interaction when one drug alters the absorption, protein binding,metabolism or excretion of another leading to altered bioavailability altering its pharmacological effect Eg magnesium reduces absorption of iron

Question 31

Steady state

Answer 31

When a drug going in to the body= drug going out of the body - achieved after 5 half lives

Question 32

Bioavailability

Answer 32

The fraction or percentage of an administered drug that reaches the systemic circulation after absorption unless given IV where it is 100% of the given dose

Question 33

Polypharmany

Answer 33

Four or more medications

Question 34

Adverse drug reaction

Answer 34

Unwanted or unintended effect Side effect = tolerable But if you need to stop drug it’s classed as an ADR

Question 35

Prescribing in the elderly

Answer 35

``` Decreased drug metabolism and excretion Altered sensitivity of some target organs Multiple pathologies Drugs with narrow therapeutic index Poor compliance Polypharmacy ```

Question 36

List goals of a medication review

Answer 36

``` NOTEARS Need + indication Open questions explore pt perceived problems, compliance, and pt opinion of effectiveness Test and monitoring Evidence + guidelines Adverse events Risk reduction + prevention Simplifications and switches ``` Reach agreement with pt and review changes

Question 37

Explain why knowledge of a pts renal function is essential before prescribing a drug which is heavily excreted by the kidney

Answer 37

``` BNF p19 Toxicity Sensitivity Increased side effects Reduced efficacy ```

Question 38

What factors can affect the ONSET of drug action, Relate this to pharmacokinetics

Answer 38

Absorption Distribution Metabolism (prodrug)

Question 39

What factors can affect the DURATION of a drug action, relate this to pharmacokinetics

Answer 39

Metabolism | Elimination

Question 40

Briefly outline the mechanisms by which the liver metabolise and eliminate drugs and the need for knowledge of liver function prior to prescribing and implications for elderly patients

Answer 40

Liver - phase 1 (oxidation, reduction, hydrolysis) phase 2 (conjugation) metabolism to make drugs more water soluble Must know the LFT results as the liver may not be working as well as expected leading to the concentration in the blood being higher and drug doses need to adjusted accordingly. Especially important in the elderly who have reduced liver function

Question 41

Briefly outline the mechanism by which the kidneys eliminate drugs, the need to know kidney function prior to prescribing and implications for elderly patients.

Answer 41

Kidney - glomerular filtration, active tubular secretion, distal reabsorption. Drug goes in the renal tubule and is excreted in urine. Must know the GRF results as the liver may not be working as well as expected leading to the concentration in the blood being higher and drug doses need to adjusted accordingly. Especially important in the elderly who have reduced liver function

Question 42

Plasma proteins can affect drug distribution. Name a plasma protein and a drug that is extensively plasma protein bound. Discuss their role in binding drugs and affecting their availability for pharmacodynamic action

Answer 42

Albumin is a plasma protein. Drugs bound to plasma protein are pharmacologically inert and do nor reach their site of action. This may mean the oral dose if far greater than needed due to the bioavailability being reduced due to the plasma protein binding. They may also be displaced by other drugs from their binding sites. Implications for pts with altered plasma protein = elderly, pregnant and malnourished pts.

Question 43

Interactions can be described as pharmacokinetic and pharmacodynamic. explain what is meant by this and give examples of each.

Answer 43

Pharmacodynamic- drugs with similar antagonistic actions and influence each other’s effects. Digoxin acts on cardiac fibres and its effects in crease if there are low levels of potassium in the blood. Frusemide is a diuretic and favours the loss of potassium when lowering the tension in the arteries. The concomitant effect can lead hypokalaemia which could result in digoxin toxicity Pharmacokinetics- interaction affecting ADME Example metoclopramide may accelerate gastric emptying and decrease the absorption of digoxin.

Question 44

Advantages and disadvantages or giving medication via the oral route

Answer 44

Easy Preferred by patients Slow release preparations may be available to extend duration of action Drugs can be formulated in such a way as to protect them from digestive enzymes - acid etc Unsuitable for pts who are uncooperative, swallowing issues or strictly nil by mouth Most oral medications are absorbed slowly Unpredictable absorption due to degradation by stomach acid and enzymes

Question 45

Advantages and disadvantages of iv route

Answer 45

Dependable and reproducible effects 100% of dose reaches systemic circulation immediately and dose accurately titrated against response Requires functioning cannula More expensive and labour intensive than other routes Cannulation distressing especially in children Iv injection of drug may cause local reaction

Question 46

Explain enzyme inhibitors

Answer 46

Attaches to an enzyme , stops it from working and decrease enzyme related process, enzyme production or enzyme activity.

Question 47

Explain enzyme inducers

Answer 47

Increase the activity of an enzyme other by binding to it or activating it carbamazepine is a liver enzyme inducer and increases the rate of elimination of the contraceptive pill

Question 48

Ion channel

Answer 48

Channel in a cell membrane where ions such as sodium can pass, target for drug action

Question 49

Prescribing a drug with the words schedule 4 next to it in the BNF what does this mean for you as a prescriber

Answer 49

It’s a controlled drug It’s a schedule 4 preparation It’s subject to controlled drug prescription writing requirements Prescription valid for 28 days only 30 days max supply best practice due to abuse potential

Question 50

You are prescribing a drug in your personal formulary when you notice a black triangle appearing next to it in the BNF, what does this mean for you as prescriber

Answer 50

It’s a newly licensed medicine It’s a drug with limited experience of use You must report ALL suspected ADRs

Question 51

What is a pro drug

Answer 51

Inactive drug that is metabolised into an active compound Codeine is a pro drug metabolised by the liver and it’s metabolite is morphine Might not be activated in pts with liver impairment as the enzymes are not there to activate it therefore drug action delayed

Question 52

Half life

Answer 52

Time it takes for the concentration of a drug in the plasma to be reduced by half Elimination takes 4-5 half lives Steady state - requires a consistent level of drug in the body (In = Out) Therefore kidney impairment will reduce excretion allowing concentration to increase in the blood (?toxicity)