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