NRNP 6566 Midterm Study Guide Week 1 to 5

1. Describe the cytochrome P450 system. Describe how inducers and inhibitors affect the cytochrome system and how that affects the half-life of medications. Cytochromes P450 (CYPs) are a superfamily of enzymes containing heme as a cofactor that function as monooxygenases. In mammals, these proteins oxidize steroids, fatty acids, and xenobiotics, and are important for the clearance of various compounds, as well as for hormone synthesis and breakdown. Cytochrome P450 enzymes can be inhibited or induced by drugs, resulting in clinically significant drug-drug interactions that can cause unanticipated adverse reactions or therapeutic failures. Fluoxetine, sertraline, and fluvoxamine are believed to inhibit cytochrome P450 2C because of observed interactions with phenytoin, diazepam, and other drugs metabolized by these enzymes. Rifampicin and isoniazid are key drugs used in the treatment of tuberculosis, while rifampicin is highly effective in inducing hepatic, drug metabolic P450 enzyme. The mnemonic SICKFACES.COM can be used to easily remember common cytochrome P450 inhibitors.