Drug Interactions

Question 1

If a patient was on atorvastatin, bisOPROLOl, CARBAMazepine, eplerenone, sacubitril/valsartan and ticagrelor, which interaction(s) would you be concerned about?

Answer 1

CARBAMazepine reduces exposure to both atorvastatin and ticagrelor.

Question 2

If a patient was on:
•	Amoxicillin/clavulanic acid
•	Aspirin
•	Candesartan/hydrochlorothiazide
•	Cholecalciferol
•	Denosumab
•	Enoxaparin
•	Esomeprazole
•	Latanoprost
•	Levothyroxine
•	Magnesium
•	Ondansetron
•	Paracetamol
•	Prazosin
•	Polystyrene sulfonate 
•	Timolol 
Would you be concerned about any interactions?

Answer 2

You may need to monitor potassium levels as candesartan and heparin can both increase potassium, while hydrochlorothiazide and ondansetron can decrease potassium.

Question 3

If a patient was on:
•	Atenolol
•	Irbesartan/hydrochlorothiazide
•	Atorvastatin
•	Multivitamin/minerals
•	Chlorvescent (Oral Potassium)
Would you be concerned about any interactions?

Answer 3

Concurrent use of irbesartan and potassium is not usually recommended. However, if necessary, monitor potassium levels, adjusting supplementation as required.

Question 4

Is there an interaction between pravastatin and sotalol?

Answer 4

No

Question 5

What are 4 factors to consider with drug-drug interactions?

Answer 5

1. PATIENT FACTORS – age, medical conditions, risk of the interaction outcome to patient
2. PHARMACOKINETICS – absorption, how the drug is metabolised by liver or excreted by kidneys, enzymes/kidneys transporters inhibited or induced
3. PHARMACODYNAMICS – mechanism of action, receptors agonised/antagonised, similar side effects which may be additive
4. TIME FACTORS – time for interaction to develop and resolve. Enzyme inhibition is generally rapid (2-3 days), whereas enzyme induction is generally slower (2 - 3 weeks)

Question 6

What is the potential interaction between citalopram and ondansetron?

Answer 6

Both citalopram and ondansetron may potentially prolong the QT interval