Interactions

Question 1

T or F, doxyclines bind to bilavlent cations and therefore should be avoided taking with calcium, iron and magnesium.

Answer 1

Doxycycline should be taken 2 hours after

Question 2

What drug inhibits the enzyme that metabolises warfarin?

Answer 2

Metronidazole is thought to inhibit CYP2C9, the enzyme that metabolises warfarin. This delayed metabolism of warfarin is thought to increase its anticoagulant effect.

Question 3

What drugs interact with ACE inhibitors and ARBs?

Answer 3

Nephrotoxic : NSAIDs, lithium, metformin, diuretics * * K + -sparing diuretics and K + supplements * * Other drugs affecting the renin– angiotensin– aldosterone system (RAAS)

Question 4

What drugs counter-interact with beta blockers?

Answer 4

Avoid verapamil

Question 5

What are some drugs that interact with CCBs?

Answer 5

Increased hypotensive effect
Increased plasma digoxin concentration
Increased plasma theophylline concentration
AEDs Reduced effect of dihydropyridine CCBs

Question 6

What are some counterinteractions with cardiac glycoside digoxin?

Answer 6

Drugs that increase risk of digoxin toxicity: –– Loop and thiazide diuretics and spironolactone –– Calcium channel blockers, amiodarone –– Quinine

Question 7

What are some drugs to be avoided with nitrates?

Answer 7

Phosphodiesterase inhibitors (e.g. sildenafil)

Question 8

What are the interactions with statins?

Answer 8

Question 9

What are the interactions with warfarin?

Answer 9

Question 10

What should co-trimaxole be avoided in?

Answer 10

Methotrexate as contains trimethoprim

Question 11

Why should a patient starting Rifampcin not take the pill?

Answer 11

Rifampicin is a potent CYP450 enzyme inducer, and therefore can increase the metabolism of a number of other medications, including combined oral contraceptives, thus reducing their efficacy. It is therefore recommended that all women should change to a form that is not affected by the drug, such as an intra-uterine device or a parenteral progestogen.

Question 12

Warfarin interacting drugs

Answer 12

Clarithromycin 500mg IV is a macrolide antibiotic and an inhibitor of the cytochrome P450 enzyme. Clarithromycin increases the anticoagulant effect of warfarin and can increase the risk of bleeding.

Question 13

What drugs cause raised CK?

Answer 13

Macrolides and statins

Question 14

What drug should not be given with BB?

Answer 14

Diltiazem and verapamil are non-dihydropyridine calcium channel blockers which are contraindicated in patients taking beta-blockers (e.g., bisoprolol) due to the risk of severe bradycardia and LV failure

Question 15

What drugs should never be given in ischemic disease?

Answer 15

Bisoprolol

Question 16

Suggest key drug interactions that should never be co-prescribed

Answer 16

Question 17

What drugs are avoided with warfarin?

Answer 17

Never - NSAIDs
Make - Metronidazole
People - Phenytoin
Quit - Quinolones
Smoking - Sulpha