Flip-Flop Kinetics — FRCA Primary MCQ
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Correct answer: E — The absorption rate is slower than the elimination rate so the terminal half-life reflects absorption not elimination
In flip-flop kinetics the rate of absorption becomes the rate-limiting step (slower than elimination). The terminal slope of the plasma concentration-time curve reflects the absorption rate constant (ka) rather than the elimination rate constant (ke). Examples: sustained-release formulations / depot injections / transdermal patches. This is a common source of confusion in PK analysis.
Reference: Peck Hill Williams 2014 Pharmacology for Anaesthesia and Intensive Care