DDIs Flashcards
Alcohol
CNS depressants Acetaminophen
Additive CNS depression, sedation, ataxia, increased risk of accidents
Increased formation of hepatotoxic metabolites of acetaminophen
Antacids
Digoxin, iron supplements, fluoroquinolones, ketoconazole, tetracyclines, thyroxine
Decreased gut absorption due either to reaction with the affected drug or due to reduced acidity
Antihistamines (H1 blockers)
Antimuscarinics, sedatives
Additive effects with the drugs affected
Barbiturates, especially phenobarbital
Azoles, calcium channel blockers, cyclosporine, propranolol, protease inhibitors, quinidine, steroids, warfarin, and many other drugs metabolized in the liver
Increased clearance of the affected drugs due to enzyme induction, possibly leading to decreases in drug effectiveness
Beta blockers
Insulin, Prazosin
Masking of symptoms of hypoglycemia Increased first-dose syncope
Bile acid-binding resins
Acetaminophen, digitalis, thiazides, thyroxine
Reduced absorption of the affected drug
Carbamazepine
Cyclosporine, doxycycline, estrogen, haloperidol, theophylline, warfarin
Reduced effect of other drugs because of induction of metabolism
Cimetidine
Benzodiazepines, lidocaine, phenytoin, propranolol, quinidine, theophylline, warfarin
Risk of toxicity due to inhibition of metabolism
Disulfiram, metronidazole, certain cephalosporins
Ethanol
Increased hangover effect due to inhibition of aldehyde dehydrogenase
Erythromycin
Carbamazepine, cisapride, quinidine, sildenafil, SSRIs
Risk of toxicity due to inhibition of metabolism
Furanocoumarins (grapefruit juice)
Alprazolam, atorvastatin, cyclosporine, midazolam
Risk of toxicity due to inhibition of metabolism
Ketoconazole and other azoles
Benzodiazepines, cisapride cyclosporine, fluoxetine, lovastatin, omeprazole, quinidine, tolbutamide, warfarin
Risk of toxicity due to inhibition of metabolism
MAO inhibitors
Catecholamine releasers (amphetamine, ephedrine), Tyramine-containing foods and beverages
Increased norepinephrine in sympathetic nerve endings released by the interacting drugs Hypertensive crisis
NSAIDs
Anticoagulants
Angiotensin-converting enzyme (ACE) inhibitors Loop diuretics, thiazides
ncreased bleeding tendency because of reduced platelet aggregation
Decreased antihypertensive efficacy of ACE inhibitor
Reduced diuretic efficacy
Phenytoin
Doxycycline, methadone, quinidine, steroids, verapamil
Reduced effect of other drugs because of induction of metabolism
Rifampin
Azole antifungal drugs, corticosteroids, methadone, sulfonylureas
Reduced effect of other drugs because of induction of metabolism
Ritonavir
Benzodiazepines, cyclosporine, diltiazem, HMG-CoA reductase inhibitors, lidocaine, metoprolol, other HIV protease inhibitors, SSRIs
Risk of toxicity due to inhibition of metabolism
Salicylates
Corticosteroids Heparin, warfarin Methotrexate
Sulfinpyrazone, probenecid
Additive toxicity to gastric mucosa
Increased bleeding tendency
Decreased clearance, causing greater methotrexate toxicity
Decreased uricosuric effect
Selective serotonin reuptake inhibitors (SSRIs)
Monoamine oxidase (MAO) inhibitors, meperidine, tricyclic antidepressants, St. John’s wort
Serotonin syndrome (hypertension, tachycardia, muscle rigidity, hyperthermia, seizures)
Thiazides
Digitalis, Lithium
Increased risk of digitalis toxicity because thiazides diminish potassium stores
Increased plasma levels of lithium due to decreased total body water
Warfarin
Amiodarone, cimetidine, erythromycin, fluconazole, lovastatin, metronidazole
Aspirin, NSAIDs, quinidine, thyroxine
Barbiturates, carbamazepine, phenytoin, rifabutin, rifampin, St. John’s wort
Increased anticoagulant effect via inhibition of warfarin metabolism
Increased anticoagulant effects via pharmacodynamic mechanisms
Decreased anticoagulant effect due to increased metabolism
