Pharmacokinetics and Pharmacodynamics of Diphenhydramine 25 mg in Young and Elderly Volunteers

Authors

  • Joseph M. Scavone,

    1. Department of Pharmacology and Experimental Therapeutics, Tufts University School of Medicine, and the Division of Clinical Pharmacology, New England Medical Center Hospital, Boston, Massachusetts.
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    • Dr. Scavone is currently with Pfizer, Inc., Groton, Connecticut

  • David J. Greenblatt,

    Corresponding author
    1. Department of Pharmacology and Experimental Therapeutics, Tufts University School of Medicine, and the Division of Clinical Pharmacology, New England Medical Center Hospital, Boston, Massachusetts.
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  • Jerold S. Harmatz,

    1. Department of Pharmacology and Experimental Therapeutics, Tufts University School of Medicine, and the Division of Clinical Pharmacology, New England Medical Center Hospital, Boston, Massachusetts.
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  • Nina Engelhardt,

    1. Department of Pharmacology and Experimental Therapeutics, Tufts University School of Medicine, and the Division of Clinical Pharmacology, New England Medical Center Hospital, Boston, Massachusetts.
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    • Dr. Engelhardt is currently in Indianapolis, Indiana.

  • Richard I. Shader

    1. Department of Pharmacology and Experimental Therapeutics, Tufts University School of Medicine, and the Division of Clinical Pharmacology, New England Medical Center Hospital, Boston, Massachusetts.
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Department of Pharmacology and Experimental Therapeutics, Tufts University School of Medicine, 136 Harrison Avenue, Boston, MA 02111.

Abstract

Thirty-seven young and elderly male and female volunteers 21 to 76 years of age received a single 25-mg oral dose of diphenhydramine or matching placebo in a double-blind, randomized, two-way crossover study. Plasma diphenhydramine concentrations, self-ratings of sedation, mood, and autonomic effects, performance on the digit-symbol substitution test (DSST), and heart rate were determined for 24 hours after administration. Information acquisition and recall were tested at 2.5 and 24 hours after administration. Age and gender did not significantly influence diphenhydramine peak plasma concentration, time of peak concentration, elimination half-life, area under the plasma concentration curve, or apparent oral clearance. Effects on psychomotor performance, sedation, mood, and memory did not differ between diphenhydramine and placebo in either group. Thus, the pharmacokinetics of single 25-mg oral doses of diphenhydramine are not influenced by age or gender. This dose of diphenhydramine produces essentially undetectable pharmacodynamic effects in both the young and elderly.

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