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Free Drug Fraction Versus Free Drug Concentration

J Clin Psychiatry 2000;61(6):449 [letter]

Letter to the Editor

Sir: In their article on pharmacokinetic considerations in the elderly, DeVane and Pollock present a wealth of valuable information for the clinician. However, a small point needs clarification. The authors state—as do many textbooks and articles on this subject—that an increase in plasma binding proteins in the elderly “can lead to a diminished free concentration of basic drugs” (italics mine).