Drug Interactions and Contraindications Flashcards
how does allopurinol work?
by inhibiting the enzyme xanthine oxidase
the same enzyme that metabolizes immunosuppressant drugs (azathioprine and mercaptopurine)
when taking what drugs together increases the risk of QT prolongation?
macrolides
quinine
amiodarone
when do contraindications occur?
when two meds interact to a point where it could potentially be fatal for the patient
what happens when 2 drugs are contraindicated?
they cannot be dispensed to the patient
what is the most common contraindication refer to?
pregnancy
when are penicillins contraindicated in patients?
when there is an established allergy
drug interaction of N-acetylcysteine?
no clinically significant drug interactions
drug interaction of acetaminophen?
they are CYP inducers, just like phenytoin and carbamazepine
they increase rate of NAPQI production/ liver toxicity, after acetaminophen overdose
drug interaction of activated charcoal?
prevents absorption of many drugs
For this reason, it is used in cases of toxicity / overdose
drug interactions of acyclovir ?
probenecid increases acyclovir concentration.
interferon increases acyclovir concentration
drug interaction of adenosine?
Dipyridamole blocks cellular uptake of adenosine.
Theophylline is a competitive antagonist at adenosine receptors.
drug interaction of epinephrine
Beta-blockers can induce widespread vasoconstriction.
drug interaction of aldosterone antagonists
ACE inhibitors; ARBs and other K-elevating drugs / supplements increase hyperkalemia risk.
drug interactions of antacids/ alginates
Divalent ions reduce serum conc. Of drugs such as bisphosphonates, levothyroxine, tetracyclines, digoxin and PPIs. Antacids increase alkalinity of urine and so increase lithium and aspirin excretion.
drug interaction of Albendazole
Plasma concentration lowered by phenytoin and carbamazepine. Cimetidine increases albendazole concentration.
drug interaction of allopurinol
Toxicity risk of mercaptopurine / azathioprine increases because allopurinol inhibits xanthine oxidase. Amoxicillin increases skin rash risk. ACE inhibitors and thiazide diuretics increase risk of hypersensitivity reactions.
drug interactions of alpha blockers
Other blood pressure lowering drugs increase risk of first-dose hypotension and hypotension risk generally thereafter.
drug reactions of aminoglycosides?
Loop diuretics / vancomycin increase ototoxicity risk. Cyclosporine, platinum chemotherapy, cephalosporins and vancomycin increase nephrotoxicity risk.
drug interactions of aminosalicylates
PPIs increase gastric pH and so may affect gastric coating of aminosalicylates. Lactulose reduces stool pH and so can prevent 5-ASA release into the intestine.
drug interaction of amidarone
Amiodarone increases plasma concentration of digoxin, diltiazem and verapamil – increasing risk of AV block, bradycardia and heart failure.
drug interaction of ACE inhibitors
Hyperkalemia risk increases when taken with other potassium-elevating drugs / supplements.Renal failure risk increases when taken with NSAIDs.
Drug interactions of Amphotericin B
- Increased risk of flucytosine toxicity.
- Increased renal toxicity with cisplatin / diuretics.
- Increased risk of hypokalemia with corticosteroids.
- Renal damage with aminoglycosides / other nephrotoxic drugs.
Drug interactions of Angiotensin-receptor blockers?
same as ACE inhibitors
Drug interactions of antidepressants (SSRIs)
- Serotonin syndrome when taken with other serotonergic drugs, such as MAO inhibitors.
- Anticoagulants increase bleeding risk of SSRIs.
- Avoid with QT prolonging drugs such as macrolides, quinine and antipsychotics.
