Basic Principles

Question 1

What are some examples of enzyme inducers?

Answer 1

Increase in enzyme activity decreases drug concentration

Increase of cytochrome P450 activity in the liver

So when prescribe particular drugs, they may affect seemingly unrelated drugs

Phenytoin
Carbamazepine
Barbiturates
Rifampicin
Alcohol
Sulfonylureas

Question 2

What is a classic example of the effects of enzyme inhibitor drugs?

Answer 2

In particular, addition of erythromycin can unpredictably cause a dangerous rise in INR if the warfarin dose is not decreased

Question 3

What are some examples of drugs which are enzyme inhibitors?

Answer 3

AODEVICES
Increase drug concentration

Allopurinol
Omeprazole
Disulfarim
Erythromycin
Valproate
Isoniazid
Ciprofloxacin
Ethanol - acute intoxication
Sulphonamides

Question 4

What drugs should be stopped before surgery?

Answer 4

I LACK OP

Insulin
Lithium
Anticoagulants
COCP/HRT
K-sparing diuretics
Oral hypoglycaemics
Perindopril/other ACE inhibitors

Question 5

When should the COCP or HRT be stopped before surgery?

Answer 5

4 weeks

Question 6

When should lithium be stopped before surgery?

Answer 6

Day before

Question 7

What should K sparing diuretics and ACEis be stopped before surgery?

Answer 7

Day of surgery

Question 8

What are the sick day rules in patients on long term corticosteroids for surgery?

Answer 8

At induction of anaesthesia, patients given IV steroids to prevent physiological stress response to surgery - resulting in profound hypotension

Question 9

What diabetic medication should be altered before surgery?

Answer 9

Patients NBM, so metformin should be stopped as will cause lactic acidosis

Oral hypoglycaemics and insulin will cause hypoglycaemia unless stopped

Sliding scale should be started - hourly monitoring and adjust hourly dose of insulin for tighter control