Basic Principles

Question 1

What must all drug prescriptions be (9)

Answer 1

legible, unambiguous (e.g no range of doses), use an approved name (e.g. salbutamol not Ventolin), In capitals, without abbreviations, signed.
If drug as ‘as required’ provide indication and max frequency or total dose in 24hrs.
if antibiotic include indication and stop/review date.
Include duration if treatment not long term

Question 2

Importance of P450 system

Answer 2

Most drugs are metabolised to inactive metabolites by the cytochrome P450 enzyme system in the liver, preventing them from having infinite effects.
However, the activity of these enzymes can be altered by drugs.
Therefore if the drug effects the P450 enzymes, it can in turn affect how quickly other drugs are metabolised, causing their effects to last longer or shorter

Question 3

Enzyme inducer effect

Answer 3

increase P450 activity, hasten metabolism so reduce the effect (therefore patients may require increased dose)

Question 4

Enzyme inhibitor effect

Answer 4

decrease enzyme P450 activity, slow down metabolism, increase the effect of the drug (therefore may require reduced dose)

Question 5

Possible effect of erythromycin on warfarin and why

Answer 5

Warfarin is metabolised by the P450 enzymes. Erythromicin is an enzyme inhibitor.
Therefore warfarin is metabolised more slowly, therefore the effect is increased, which can cause a dangerous rise in INR (meaning blood is taking a long time to clot). Therefore warfarin dose should be decreased.
NOTE: be aware of this in patients with excessive anticoagulation

Question 6

Common Enzyme Inducers

Answer 6

NOTE: enzyme inducers, metabolised quicker, drug conc decreased and therefore less effective
PC BRAS
Phenytoin
Carbamazepine
Barbiturates
Rifampicin
Alcohol (chronic excess)
Sulphonylureas

Question 7

Common enzyme inhibitors

Answer 7

NOTE: enzyme inhibitors, metabolised slower, drug conc increased and therefore more effective
AODEVICES:
Allopurinol
Omeprazole
Disulifiram
Erythromycin
Valporate
Isoniazide
Ciprofloxacin
Ethanol (acute intoxication)
Sulphonamides

Question 8

Phenytoin drug class and indication

Answer 8

Anticonvulsant
Prevention and treatment of seizures (tonic clonic, focal, after injury or surgery, status epilepticus)

Question 9

Carbamezipine drug class and indication

Answer 9

Anticonvulsant
Tonic clonic seizures, trigeminal neuralgia, prophylaxis of bipolar disorder unreactive to lithium, diabetic neuropathy, adjust in alcohol withdrawal

Question 10

Barbiturates Drug class, examples and indication

Answer 10

sedative-hypnotic
Amobarbital, Butalbital, Methohexital, Pentobarbital, Phenobarbital, Primidone
Secobarbital
Range of uses - insomnia, epilepsy (pheno, primi), tremor, neonatal withdrawal

Question 11

rifampicin drug class and indication

Answer 11

Antibiotic, antimycobacterial (inhibit DNA-dependant RNA polymerase)
Tuberculosis, endocarditis, HiB

Question 12

Sulphonylureas example, indication, mechanism

Answer 12

e.g gliceride, glipizide, glimepiride, tolbutamide
T2DM, second line after metformin
Stimulate release of insulin from beta cells

Question 13

Allopurinol drug class and indication

Answer 13

Xanthine oxidase inhibitors
prophylaxis of gout/hyperuricaemia

Question 14

Omeprazole drug class and indication

Answer 14

Proton-pump inhibitor (PPI)
H-pylori, prevention of gastric ulcers NSAID duodenal disorder, prophylaxis of NSAID treatment, GORD

Question 15

Disulifiram indication

Answer 15

Adjunt in alcohol dependence

Question 16

Erythromycin class, mechanism

Answer 16

macrolide antibiotic
inhibit protein synthesis, bind to 50S ribosome subunit

Question 17

Valporate drug class and indication

Answer 17

anticonvulsant
epilepsy, migraine prophylaxis

Question 18

Isoniazid class and indication

Answer 18

Antibiotic
Tuberculosis

Question 19

Ciprofloxacin class and mechanism

Answer 19

Fluroquinolone antibiotic
inhibit enzyme activity to prevent cell division
bacterial eye infection, otitis externa, Resp tract infections, UTI etc

Question 20

Sulphonamides mechanism, example

Answer 20

inhibit enzyme DHPS
‘sulpha drugs’ - sulfamethazine, sulfadiazine etc

Question 21

Drug to increase before surgery and why

Answer 21

long term corticosteroid (e.g. prednisolone), commonly have adrenal atrophy so won’t mount an adequate ‘stress’ response to surgery, resulting in profound hypotension. similar to ‘sick day rules’ where dose should be doubled if ill, patients should have IV steroids at the induction of anaesthesia

Question 22

Drugs to stop before surgery

Answer 22

I LACK OP
Insulin
Lithium
Anticoagulants/antiplatelets
COCP/HRT
K-sparing diuretics
Oral hypoglycaemic
Perindopril and other ACE-inhibitors

Question 23

Examples of anticoagulants

Answer 23

apixaban, dabigatran, rivoroxaban, warfarin, heparin

Question 24

Examples of anti-platelets

Answer 24

Acetylsalicylic acid (aspirin), clopidogrel, prasugrel, ticegralor

Question 25

Examples of K-sparing diuretics

Answer 25

Spironolactone, Eplerenone, Amiloride, Triamterene

Question 26

examples or oral hypoglycaemics

Answer 26

slufonylureas (glipizide, glyburide, gliclazide, glimepiride), meglitinides repaglinide and nateglinide), biguinides (metformin), thiazolidinediones (rosiglitazone, pioglitazone), DPP-4 inhibitors (Sitagliptin, lingagliptin), SGLT2 inhibitors (dapagliflozin and canagliflozin)

Question 27

When to stop COCP and HRT

Answer 27

4 weeks before surgery

Question 28

When to stop lithium

Answer 28

day before surgery

Question 29

when to stop K-Sparing diuretics

Answer 29

Day of surgery

Question 30

when to stop ace-inhibitors

Answer 30

day of surgery

Question 31

When to stop anticoagulants and antiplatelets

Answer 31

variable (don’t need to memorise)

Question 32

when to stop oral glycemic drugs and insulin

Answer 32

variable (don’t need to memorise)

Question 33

why should metformin/oral hypoglycaemic be stopped before surgery

Answer 33

patients are nil by mouth, so if given metformin will cause lactic acidosis
other oral hypoglycaemic and insulin will cause hypoglycaemia unless stopped.
insulin should be delivered on a sliding scale, and glucose levels checked every hour