European Journal of Clinical Pharmacology

, Volume 27, Issue 1, pp 23–27 | Cite as

Evidence for a peripheral component in the sympatholytic actions of clonidine and guanfacine in man

  • M. B. Murphy
  • M. J. Brown
  • C. T. Dollery
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Summary

The time courses of the changes in plasma growth hormone and noradrenaline concentrations in response to 15 min infusions of clonidine 0.2 mgs and guanfacine 2 mgs, were studied in six normal volunteers, in a double-blind, randomised, crossover study. Plasma noradrenaline fell within 15 min of the commencement of drug administration, by 36±14% after clonidine (p<0.05) and by 32±11% (p<0.05) after guanfacine. Plasma growth hormone was not significantly elevated until the 30th minute to 12.0±4.7 lU/ml (p<0.05) after clonidine and 14.7±11.5 lU/ml (p<0.05) after guanfacine, having been undetectable prior to both drugs. The reduction in plasma noradrenaline by these α2-adrenergic agonists, prior to activation of central adrenoceptors as detected by changes in plasma growth hormone, is evidence for a peripheral component in their sympatholytic effect.

Key words

hypertension alpha2-adrenoceptors blood pressure clonidine guanfacine healthy volunteers 

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Copyright information

© Springer-Verlag 1984

Authors and Affiliations

  • M. B. Murphy
    • 1
  • M. J. Brown
    • 1
  • C. T. Dollery
    • 1
  1. 1.Department of Clinical Pharmacology, Royal Postgraduate Medical SchoolHammersmith HospitalLondonEngland

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