HLSC 3P19 Lecture Notes - Lecture 3: Grapefruit Juice, Rifampicin, Itraconazole
15 Dec 2019
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Competition: substrates compete for the enzymes they are metabolized by. If two drugs that are metabolized by the same enzyme are given concurrently, the drug levels will remain higher and longer. Enzyme induction and enzyme inhibition: drugs and other substances can stimulate or inhibit the genes involved in the synthesis of cyp enzymes. Drugs such as rifampin and barbiturates are potent inducers. They lead to the production of more cyp enzymes, which in turn results in faster elimination of drugs that are metabolized by those cyp enzymes. Lower than expected drug levels can account for treatment failure. Drugs such as cimetidine, erythromycin, and itraconazole are potent inhibitors of cyp enzyme synthesis. They will slow down the elimination of drugs that are metabolized by those enzymes. Higher than expected drug levels can account for drug toxicity (undesirable side-effects) Drugs are made more water soluble by conjugation: glucuronidation by glucuronosyltransferases, acetylation by n-acetyltransferase, sulfation by sulfotransferases glycation.
