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Thiopentone Redistribution Offset — FRCA Primary MCQ

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EasyPharmacology - Intravenous AnaestheticsThiopentone Redistribution OffsetFRCA Primary

Regarding thiopentone redistribution accounts for its short duration of clinical effect. After a single bolus the plasma concentration falls because:

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Correct answer: B — The drug redistributes from the vessel-rich group (brain) to the muscle group

After IV injection thiopentone rapidly enters the brain (vessel-rich group) due to high blood flow and lipid solubility. Consciousness is lost within 30 seconds (one arm-brain circulation time). The brain concentration then falls as the drug redistributes to the muscle group (larger volume / moderate blood flow). Metabolism is slow (hepatic oxidation / t½ 11 hours).

Reference: Peck Hill Williams 2014 Pharmacology for Anaesthesia and Intensive Care