Vd Plasma Compartment — FRCA Primary MCQ

Correct answer: B — Plasma

A Vd of approximately 3 L in a 70 kg adult corresponds to the plasma volume. Drugs confined to plasma are typically highly protein-bound or very large molecules (e.g. heparin Vd ~4 L). Extracellular fluid is ~14 L / total body water ~42 L / and drugs with extensive tissue binding have Vd >> 42 L.

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