The FlightBridgeED Podcast E121: Pharmacokinetics, Pharmacodynamics, and Plasma Protein Binding
Dec 19, 2017
Explore the fascinating world of pharmacokinetics and pharmacodynamics, where medications undergo complex processes after administration. Learn how lipid solubility affects drug absorption using fun analogies. Discover the impact of plasma protein binding on drug availability and how competitive interactions can alter treatment outcomes. Eric also compares various drugs like fentanyl and morphine, revealing risks associated with high protein binding, especially in anesthesia. It's a deep dive made easy, unraveling the science behind effective medication management.
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Lipid Solubility Drives Absorption
- Lipid solubility controls how quickly drugs cross cell membranes and reach targets.
- Lipophilic drugs diffuse through the double phospholipid membrane far faster than hydrophilic ones.
First-Pass Cuts Oral Drug Bioavailability
- First-pass metabolism after PO or rectal dosing sends drug through the portal vein to the liver before systemic circulation.
- This reduces bioavailability compared with IV, IM, or sublingual routes which enter systemic circulation first.
Bioavailability Depends On Route
- Bioavailability equals the fraction of drug that reaches plasma unchanged.
- IV and many parenteral routes give ~100% bioavailability while PO can drop to ~10–50% due to first-pass loss.