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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 ❄️.
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