Extra Info Flashcards
What is hyoscine butylbromide the first line treatment for?
IBS
How does salbutamol affect potassium levels?
Can increase cellular uptake –> reduced plasma levels -> hypokalaemia
Which drugs can beta blockers not be used with?
Non-dihydropyridine calcium channel blockers! E.g. verapamil, diltiazem. Can cause HF, bradycardia and even asystole
How may oral calcium affect the absorption of other drugs?
Iron, bisphosphonates, tetracyclines and levothyroxine
What interaction must you be careful of when prescribing calcium channel blockers?
That they’re not on a beta blocker. Verapamil and diltiazem can cause HF with this interaction
Which antibiotics may increase the action of warfarin?
Cephalosporins and carbapanems
What drugs may reduce the activation of clopidogrel?
Drugs that inhibit cytochrome P450: PPIs (omeprazole), ciprofloxacin, erythromycin, fluconazole, SSRI
What drug interaction may reduce the efficacy of systemic corticosteroids?
Cytochrome P450 enzyme inducers: phenytoin, carbamazepine, rifampicin
Which drugs can increase the risk of digoxin toxicity?
Loop and thiazide diuretics as they can cause hypokalaemia OR amiodarone, CCB, spironolactone and quinine can increase plasma levels –> increased risk of toxicity
What is the first line treatment following a TIA?
Dipyridamole
What main drug does dipyridamole interact with?
Adenosine - inhibits its cellular uptake –> increased effects on heart –> increases risk of cardiac arrest
What are fibrinolytic drugs?
Dissolve fibrinous clots and re-canalise occluded vessels
When are fibrinolytic drugs used?
> In acute ischaemic stroke (alteplase within 4.5 hours)
Acute STEMI within 12 hours if PCI not available
Massive PE with haemodynamic instability
In major bleeding associated with unfractionated heparin therapy, what drug can be given to reverse the anticoagulation
Protamine
How may iron supplements affect other medications?
Reduce the absorption of levothyroxine and bisphosphonates. These drugs should be taken at least 2 hours before oral iron
Which drugs inhibit cytochrome P450?
PPIs (omeprazole), ciprofloxacin, erythromycin, fluconazole, SSRI, metronidazole
What drugs increase the QT interval?
Amiodarone, antipsychotics, quinine, SSRIs
What is the major interaction to know about for metformin?
Can’t be taken with IV contrast media, metformin must be withheld for 48hrs. As there is increased risk of renal impairment, metformin accumulation and lactic acidosis
What’s the relationship between metformin and IV contrast media?
Can’t be taken with IV contrast media, metformin must be withheld for 48hrs. As there is increased risk of renal impairment, metformin accumulation and lactic acidosis
What’s the mechanism of action of nicorandil?
Arterial and venous vasodilator through nitrates and activation of K+ ATP channels
What’s an important drug interaction of nicorandil?
Sildenafil (viagra) - can’t be used together –> major hypotension
Which drug interacts with nitrates?
Sildenafil –> major vasodilatation –> hypotension
How may rifampicin interact with the oral contraceptive pill?
it’s a cytochrome P450 inducer –> can reduce efficacy of contraceptive pill, particularly progesterone only forms
What drugs can penicillin interact with?
Methotrexate and warfarin
How can penicillin affect warfarin?
Can increase the effect of warfarin by killing normal GI flora that synthesises vitamin K
How can penicillin affect methotrexate levels?
Penicillins reduce renal excretion of methotrexate –> accumulation and toxicity may develop
What electrolyte disturbance may trimethoprim cause?
Hyperkalaemia
Which drugs, when co-prescribed with vancomycin, increase the likelihood of ototoxicity and/or nephrotoxicity?
Aminoglycoside, loop diuretics, ciclosporin
Which drugs are cytochrome P450 inducers?1
Phenytoin, carbamazepine, rifampicin
Which drugs are metabolised by cytochrome P450 enzymes?
COW PATS > Ciclosporin > Oral contraceptive pill > Warfarin > Phenytoin > ACh esterase inhibitors (e.g. Donepezil) > Theophylline > Statins & steroids
What drug interaction may occur with spironolactone?
High risk of hyperkalaemia if used with ACEi or ARBs (K+ elevating drugs)
What happens if ACEi/ARBs are used alongside NSAIDs?
Increases risk of renal failure
