In alcohol toxicology, the Widmark equation is used to back-calculate blood alcohol concentration (BAC) at an earlier time. The Widmark 'r' factor (distribution factor) differs between males (0.68) and females (0.55). This difference is PRIMARILY due to which physiological characteristic?

• A Women have higher activity of gastric alcohol dehydrogenase
• B Women have faster hepatic alcohol metabolism
• C Women have higher plasma protein binding of ethanol
• D Women have a lower proportion of total body water relative to body weight ✓

Explanation

Ethanol is highly water-soluble and distributes into total body water. Women have a higher proportion of body fat and lower total body water per kilogram than men; therefore, a given dose of alcohol produces a higher BAC in women, reflected by a lower Widmark 'r' (volume of distribution) factor of 0.55 vs. 0.68 in men. Women actually have lower, not higher, gastric ADH activity. Protein binding of ethanol is negligible.

Reference: The Essentials of Forensic Medicine and Toxicology (Narayan Reddy), 34th ed.

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