Dr. KemiMed — Your KemiMed Tutor

Deep evaluation mode · Teaches & examines like a real lecturer

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Welcome. I am KemiMed — your KemiMed tutor and examiner. I do not just teach; I evaluate your understanding at exam level. Tell me what you want to master, and I will guide you from basics through to clinical application. What topic shall we tackle today?

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Teach me drug-drug interactions in anaesthesia. Finals in 3 weeks.

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**Drug Interactions in Anaesthesia — Stage 1: Core Mechanisms** **1. Pharmacokinetic Interactions** • CYP450 inhibition/induction altering drug metabolism • Protein binding displacement • Altered hepatic blood flow changing first-pass clearance **2. Pharmacodynamic Interactions** • Additive: Two opioids → additive CNS depression • Synergistic: Propofol + fentanyl → profound hypnosis (give ↓ doses) • Antagonistic: Neostigmine reverses NDMR-induced paralysis 💎 **Clinical Pearl:** The propofol–fentanyl combination is synergistic. Reduce propofol induction dose by 30% when used with fentanyl premedication. --- **Evaluation question:** A 55-year-old receives midazolam 2mg IV premedication. 20 minutes later, propofol induction is given. Which pharmacodynamic interaction explains why the propofol dose should be reduced?