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CYTOCHROME P-450 BASED DRUG INTERACTION.pptx
- 2. INTRODUCTION ABOUT CYTOCHROME P-450. Cytochrome P450 (CYP) enzymes are a large family of heme-thiolate monooxygenases found primarily in the liver, but also present in other tissues such as the intestines, lungs, and kidneys. They play a crucial role in the metabolism of drugs and other xenobiotics, as well as in the biosynthesis of cholesterol, steroids, and other lipids. Drug interactions involving CYP enzymes are a significant concern in clinical pharmacology, as they can lead to altered drug efficacy or increased toxicity. These enzyme are responsible for breakdown of wide range of substances including medications, toxins, even Hormones. i.e.., endogenous compound. They need NADPH and O2 for their work or action. This cause rise or decline i.e., alternation in the blood level and efficacy of the affected drug, potentially leading to the ADR effect or therapeutic failure. Many drug interaction are result in Drug inhibition or induction of CYP enzyme. Drug interaction, involving Cytochrome P-450 enzyme occurs, when one drug affect the metabolisms of another drug by inducing or inhibiting the activity of specific Cytochrome P- 450 enzyme.
- 3. MECHANISMS OF DRUG INTERACTIONS Drug interactions involving CYP enzymes can occur via two main mechanisms: enzyme inhibition and enzyme induction Drug interaction Drug Inhibition Non- Competitive inhibitor Competitive inhibitor Un- Competitive Inhibitor Drug Induction
- 4. ENZYME INHIBITION Inhibition of CYP-450 by different drug or diff-diff drug interaction is called Inhibition. If two drug are substrate for same CYP is-enzyme then metabolism of one or both the drugs may be delayed. Example :- Erythromycin and midazolam both are substrate of 3A4 isoenzyme. So there is competition for binding site and at last metabolisms of midazolam in inhibition. Cimitidine and Ketoconazole binds to Cytochrome P-450 and completely inhibit the metabolism of Testosterone.
- 5. TYPES OF ENZYME INHIBITION Types of Enzyme Inhibition Competitive inhibitor Non- Competitive inhibitor Un- Competitive Inhibitor
- 6. Binds to the Active site Km = Increase Vmax = No effect (It remain same) Eg:- statin drugs Competitive in HMG-CO- Reeducates enzyme For cholesterol synthesis Binds to the Allosteric site Km = unchanged Vmax = Decrease Eg., Heavy metal (Mercury) Binds to sulfhydryl group on enzyme. Binds to the Allosteric site Km = Decrease Vmax = Decrease Eg., Certain drug used for Cancer Treatment.
- 7. DRUG INDUCTION Induction of CYP-450 enzyme by drugs and pollutants Some certain drugs can induce the activity of specific CYP-450 enzymes, resulting in increased metabolisms of other drugs that are substrate for those enzymes. Example:- Phenobarbitone, Rifampicin (CYP3A4 inducer), Smoking (IA2 inducer i.e.., Theophylline), DDT, Alcohol, Phenytoin (CYP2C9 Inducer) Drug Induction Auto induction If a drug induces its own metabolism = Auto induction Eg :- Carbamazapine Foreign induction If the induction by other compound = foreign induction Eg :- Griseofluvin.