Units 1-8 principles

Question 1

Drugs either work via … or …

Answer 1

Receptors: agonist; antagonist
Enzymes: ACEi

Question 2

When do pharmacodynamic interactions happen

Answer 2

2 drugs work via different pathways to have the same effect

Question 3

Principles of pharmacokinetics (ADME)

Answer 3

Absorption
Distribution
Metabolism
Elimination

Question 4

Lipophilic drugs are distributed

Answer 4

Around the whole body

Question 5

Hydrophilic drugs

Answer 5

Stay in the plasma

Question 6

The most important enzyme involved in metabolism

Answer 6

P450 system

Question 7

The two phases of metabolising drugs from lipophilic to hydrophilic in the liver

Answer 7

Phase I - oxidation/reduction/hydrolysis

Phase II - conjugation with glucuronide/sulphate

Question 8

Inducers of P450 system

Answer 8

Carbamazepine 
Phenytoin 
Rifampicin 
Chronic alcohol intake 
Barbecued meat 
St John’s Wort

Question 9

Inhibitors of P450 system

Answer 9

Erythromycin 
Ciprofloxacin 
Miconazole 
Sodium valproate 
Grapefruit juice 
Cranberry juice

Question 10

Which type of drugs are excreted unchanged

Answer 10

Hydrophilic

Question 11

Drugs that are metabolised into active metabolites and may accumulate in liver failure

Answer 11

Opioids

Question 12

Therapeutic window

Answer 12

Range in which the drug is clinically effective without causing toxic side effects

Question 13

Drug half-life

Answer 13

Time taken for plasma concentration of a drug to decrease to 50% of its original value

Question 14

A steady state of a drug is reached after how many half-lives

Answer 14

4

Question 15

Why is a loading dose necessary for drugs with a long half-life

Answer 15

Drugs with long half-lives take longer to reach steady state

Question 16

4 cases of drug monitoring

Answer 16

• cannot predict how much drug px requires
• narrow therapeutic window
• if symptoms are due to side effects
• concern that px is not taken the drug

Question 17

Examples of monitored drugs

Answer 17

Digoxin 
Lithium 
Carbamazepine 
Phenytoin 
Theophylline 
Certain IV antimicrobials

Question 18

Pros oral

Answer 18

Convenience

Question 19

Cons oral

Answer 19

• nauseated px
• NBM/swallowing problems
• first pass metabolism
• compliance
• time to reach steady state

Question 20

Pros rectal, sublingual & buccal

Answer 20

• avoids first pass metabolism
• good for nauseated/NBM
• no need for IV access
• topical tx

Question 21

Cons rectal, sublingual & buccal

Answer 21

Local irritation

Question 22

Pros IV

Answer 22

• fast
• reliable
• bolus or infusion

Question 23

Cons IV

Answer 23

• requires IV access
• drugs reactions common
• avoid in IVDUs

Question 24

Pros IM

Answer 24

• fast
• reliable
• no IV access needed

Question 25

Cons IM

Answer 25

- painful | - not if clotting problems

Question 26

Pros subcutaneous

Answer 26

- avoids first pass metabolism - no IV access needed - relatively painless - px can self-inject

Question 27

Cons subcutaneous

Answer 27

- local irritation - px acceptability - needle-phobias

Question 28

Pros topical

Answer 28

- avoids first pass - px acceptability - avoid systemic side effects

Question 29

Cons topical

Answer 29

- local irritation | - require adequate technique/appropriate dosing

Question 30

Consider this safety aspect when prescribing

Answer 30

ALLERGY

Question 31

Compliance

Answer 31

Extent to which px behaviour matches prescriber’s recommendations

Question 32

Adherence

Answer 32

Extent to which px behaviour matches agreed recommendations form prescriber

Question 33

Concordance

Answer 33

Consultation process in which doctor and patient agree therapeutic decisions that incorporate their perspective views

Question 34

Five divisions of side effects

Answer 34

``` Predictable Bizarre Chronic Delayed End of treatment effects ```

Question 35

When does prescribing cascade happen

Answer 35

Medication given to counteract the side-effects of another medication

Question 36

Safety wise, attention should be paid with what 4 drugs in particular

Answer 36

Insulin Opiates Warfarin DOACs

Question 37

4 potential fates of drugs in terms of first metabolism (absorption)

Answer 37

- not metabolised before entering general circulation - substantially metabolised but that can be overcome by prescribing large amounts - completely metabolised before entering circulation (GTN) - become active after 1st pass

Question 38

A hydrophilic drug such as digoxin is prescribed in the same quantities in a 90kg or a 65kg. How so without accounting for the extra weight?

Answer 38

Extra weight is fat

Question 39

Int ems of drug safety, what are the characteristics of drugs that make you worry in terms of P450 interactions

Answer 39

- narrow therapeutic window | - old-fashioned drugs

Question 40

Why should you initially start slow and then increase the dose of carbamazepine and phenytoin

Answer 40

They induce their own metabolism

Question 41

Drugs the patient is on that should make you alert regarding interactions

Answer 41

``` Warfarin Theophylline Carbamazepine Phenytoin OCP ```

Question 42

4 general considerations when prescribing a new medication

Answer 42

Allergy Comorbidities & drug interaction Pregnancy/breastfeeding Hepatic/renal failure

Question 43

Alternative classification of drug administration

Answer 43

Enteral: GI tract eg oral/rectal Parenteral: non-GI eg IV/IM/subcutaneous Topical

Question 44

Patient-centred factors for non-compliance

Answer 44

Age Psycho-social factors Ethnicity Patient-prescriber relationship

Question 45

Therapy-centred factors for non-compliance

Answer 45

Route of administration Duration of treatment Complexity of regime Side effects

Question 46

Five types of side effects of drugs

Answer 46

Type A: predictable, common & rarely fatal Type B: unpredictable, rare, fatal (can be), should document Type C: chronic, taking meds for too long Type D: delayed, uncommon, after completing tx Type E: end-of-tx, if stopped abruptly

Question 47

2 Abx please look for them for P450 interaction

Answer 47

Ciprofloxacin | Clarythromycin