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Enzyme inducers and inhibitors
🧪 Enzyme Inducers & Inhibitors
🔑 Inducers → speed up metabolism → 💊 treatment failure.
🔑 Inhibitors → slow down metabolism → ☠️ drug toxicity.
📖 About
- Cytochrome P450 (CYP450) enzymes are mainly found in the liver 🏥.
- They mediate phase I metabolism (oxidation, reduction, hydrolysis).
- Different isoenzymes (e.g. CYP3A4, CYP2C9, CYP2D6) handle different drugs.
⚖️ Induction vs Inhibition
- 🚀 Inducers: Increase CYP450 activity → faster drug breakdown → reduced plasma levels → loss of effect.
- ⛔ Inhibitors: Block CYP450 activity → slower breakdown → increased plasma levels → toxicity risk.
💉 Warfarin as an Example
- ⬇️ Inducers lower warfarin levels → ↓ INR → clotting risk (e.g. carbamazepine, phenytoin, rifampicin, St John’s Wort).
- ⬆️ Inhibitors raise warfarin levels → ↑ INR → bleeding risk (e.g. macrolides, ciprofloxacin, amiodarone, azoles, cimetidine).
🔥 Common Enzyme Inducers (↓ Drug Effect)
- 💊 Phenytoin
- 💊 Carbamazepine
- 💊 Barbiturates
- 💊 Rifampicin
- 🍺 Chronic alcohol use
- 🌿 St John’s wort
❄️ Common Enzyme Inhibitors (↑ Drug Toxicity)
- 💊 Allopurinol
- 💊 Omeprazole
- 💊 Disulfiram
- 💊 Erythromycin (and other macrolides)
- 💊 Valproate
- 💊 Isoniazid
- 💊 Ciprofloxacin
- 💊 Cimetidine
- 🍷 Acute alcohol intake
- 💊 Sulfonamides
💡 Clinical Pearls
- Always consider CYP450 interactions when prescribing drugs with narrow therapeutic index (e.g. warfarin, ciclosporin, theophylline, digoxin, tacrolimus).
- Remember: CRAP GPS (Carbamazepine, Rifampicin, Alcohol (chronic), Phenytoin, Griseofulvin, Phenobarbital, St John’s wort) = classic inducers 🚀.
- Think: SICKFACES.COM (Sodium valproate, Isoniazid, Cimetidine, Ketoconazole, Fluconazole, Alcohol (acute), Ciprofloxacin, Erythromycin, Sulfonamides, Chloramphenicol, Omeprazole, Metronidazole) = common inhibitors ❄️.
| The content on this website is provided for educational and informational purposes only to support exam preparation (e.g., MLA, MRCP, USMLE) and learning. This is NOT medical advice, diagnosis, treatment, or professional guidance. It does not replace consultation with a qualified healthcare professional, official guidelines (e.g., NICE, GMC, BNF), or supervised clinical practice. Always verify information with current, authoritative sources. Makindo and its contributors accept no liability for any reliance on this content, including errors, omissions, or any resulting harm, loss, or consequences. By using this site, you agree to these terms. |
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