Sedation and histamine H1-receptor antagonism: studies in man with the enantiomers of chlorpheniramine and dimethindene

Br J Pharmacol. 1991 Sep;104(1):270-6. doi: 10.1111/j.1476-5381.1991.tb12418.x.


1. The effects of 10 mg (+)- and (-)-chlorpheniramine and 5 mg (+)- and (-)-dimethindene on daytime sleep latencies, digit symbol substitution and subjective assessments of mood and well-being were studied in 6 healthy young adult humans. Each subject also took 5 mg triprolidine hydrochloride as an active control and two placebos. 2. Daytime sleep latencies were reduced with triprolidine, (+)-chlorpheniramine and (-)-dimethindene, and subjects also reported that they felt more sleepy after (+)-chlorpheniramine and (-)-dimethindene. Performance on digit symbol substitution was impaired with (+)-chlorpheniramine. 3. Changes in measures with (-)-chlorpheniramine and (+)-dimethindene were not different from changes with placebo. 4. In the present study, changes in measures of drowsiness and performance were limited to the enantiomers with high affinity for the histamine H1-receptor. These findings strongly suggest that sedation can arise from H1-receptor antagonism alone, and provide further support for the belief that the histaminergic system is concerned with the regulation of alertness in man.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Affect / drug effects
  • Animals
  • Bronchodilator Agents / pharmacology
  • Chlorpheniramine / metabolism
  • Chlorpheniramine / pharmacology*
  • Dimethindene / metabolism
  • Dimethindene / pharmacology*
  • Female
  • Guinea Pigs
  • Histamine / pharmacology
  • Histamine H1 Antagonists / pharmacology*
  • Humans
  • Hypnotics and Sedatives / pharmacology*
  • In Vitro Techniques
  • Male
  • Molecular Conformation
  • Psychomotor Performance / drug effects
  • Radioligand Assay
  • Receptors, Histamine H1 / metabolism
  • Sleep / drug effects
  • Sleep Stages / drug effects
  • Stereoisomerism
  • Triprolidine / pharmacology


  • Bronchodilator Agents
  • Histamine H1 Antagonists
  • Hypnotics and Sedatives
  • Receptors, Histamine H1
  • Triprolidine
  • Chlorpheniramine
  • Dimethindene
  • Histamine