Prescribing

Question 1

If you are prescribing a PRN drug what two instructions do you need to give?

Answer 1

If a drug is to be used ‘as required’ provide two instructions: (1) indication and (2) a maximum frequency (e.g.
twice daily) or total dose in 24 hours (e.g. 1g)

Question 2

The drugs effect on the body…

Answer 2

Pharmacodynamics

Question 3

What the body does to the drug…

Answer 3

Pharmacokinetics (absorption, metabolism, excretion)

Question 4

PC BRAS

Enzyme inducers

Answer 4

↑ Enzyme Activity→
↓ Drug Concentration

PC BRAS:
Phenytoin, Carbamazepine,
Barbiturates, Rifampicin,
Alcohol (chronic excess),
Sulphonylureas

Question 5

AO DEVICES

Enzyme inhibitors

Answer 5

↓ Enzyme Activity→↑ Drug Concentration

KAODEVICES:
Ketoconazole
Allopurinol
Omeprazole
Disulfiram
Erythromycin
Valproate
Isoniazid
Ciprofloxacin
Ethanol (acute intoxication)
Sulphonamides

+ GRAPEFRUIT

Question 6

Drugs to increase during surgery

Answer 6

Steroids (should be given IV before induction of anaesthesia)

Question 7

Drugs to stop before surgery

Answer 7

Combined oral contraceptive pill (COCP)
and hormone replacement therapy (HRT)
= 4 weeks before
surgery

Lithium = Day before
Potassium-sparing diuretics and
ACE-inhibitors = Day of surgery

Anticoagulants (warfarin/heparin
including prophylactic dose) Antiplatelets
(aspirin/clopidogrel/dipyridamole) = variable (occasionally
continued during
surgery)

Oral hypoglycaemic drugs and insulin = variable

Question 8

Why to stop oral hypoglycaemic drugs prior to surgery

Answer 8

Patients are nil by mouth

Metformin = risk of lactic acidosis
Other oral hypoglycaemics
and insulin = risk of hypoglycaemia

A sliding scale should be started instead where hourly blood glucose monitoring adjusts the hourly dose of insulin given to provide much tighter control

Question 9

Drugs that cause hyperkalaemia (5)

Answer 9

Spironolactone
ACEI
ARBs
Heparin
Trimethoprim

Question 10

Drugs that cause hypokalaemia (6)

Answer 10

Loop diuretics
Thiazide
Chronic laxative treatment
Prednisolone
Insulin
B-blocker

Question 11

PReSCRIBER mnemonic for reviewing prescriptions

Answer 11

● Patient details
● Reaction (i.e. allergy plus the reaction)
● Sign the front of the chart
● check for Contraindications to each drug
● check Route for each drug
● prescribe Intravenous fluids if needed
● prescribe Blood clot prophylaxis if needed
● prescribe antiEmetic if needed and
● prescribe pain Relief if needed.

Question 12

What drug should be given in the day as it can lead to insomnia?

Answer 12

Steroids

Question 13

Drug indicated in acute dystonic reactions?

Answer 13

Procyclidine hydrochloride