Cytochrome P450 enzyme inducers and inhibitors and the drug interactions they cause tested on USMLE Step 1.
35 cards · basic cards · AI-written, checked twice. Edit anything.
- Which CYP450 isoenzyme is the most abundant in the liver and metabolizes the largest number of drugs?
- CYP3A4
- Rifampin induces CYP450 enzymes, which can cause failure of what commonly used medication class?
- Oral contraceptives
- How does chronic phenytoin use (a CYP450 inducer) affect warfarin's anticoagulant effect?
- It decreases warfarin's anticoagulant effect by increasing its metabolism
- Carbamazepine is well known for inducing the metabolism of which drug, including itself over time?
- Itself (autoinduction)
- Phenobarbital, like other barbiturates, has what effect on hepatic CYP450 enzymes?
- It induces them
- Chronic alcohol use induces which CYP450 enzyme?
- CYP2E1
- St. John's Wort induces CYP3A4, which can reduce the effectiveness of which transplant immunosuppressant?
- Cyclosporine
- Griseofulvin, an antifungal drug, has what effect on hepatic CYP450 enzymes?
- It induces them
- Cigarette smoking induces CYP1A2, which lowers serum levels of which bronchodilator drug?
- Theophylline
- Cimetidine is known as a potent, broad inhibitor of CYP450 enzymes, potentiating the effect of which anticoagulant?
- Warfarin
- Azole antifungals such as ketoconazole have what effect on CYP3A4?
- They inhibit it
- Which two macrolide antibiotics are potent CYP3A4 inhibitors, unlike a third macrolide that is not?
- Erythromycin and clarithromycin (azithromycin does not significantly inhibit CYP450)
- Ritonavir is used at low doses in HIV therapy specifically to inhibit which enzyme and boost other protease inhibitor levels?
- CYP3A4
- Grapefruit juice inhibits intestinal CYP3A4, increasing the oral bioavailability of which two drug classes?
- Statins and calcium channel blockers
- Combining simvastatin with clarithromycin (a CYP3A4 inhibitor) increases the risk of what adverse effect?
- Myopathy or rhabdomyolysis