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Goodman & Gilman's The Pharmacological Basis of Therapeutics, 11e
| II. Drugs Acting at Synaptic and Neuroeffector Junctional Sites > |
 2-Selective Adrenergic Receptor Agonists
Sections:  2-Selective
Adrenergic Receptor Agonists, Clonidine, Pharmacological
Effects, Absorption,
Fate, and Excretion, Adverse Effects, Therapeutic
Uses, Apraclonidine, Brimonidine, Guanfacine, Guanabenz, Methyldopa, Tizanidine.
Topics Discussed: adrenergic alpha-agonists; adrenergic alpha-antagonists; apraclonidine hydrochloride; brimonidine tartrate; clonidine; guanabenz; guanfacine; methyldopa and methyldopate hcl; tizanidine.
Excerpt:
"2-Selective adrenergic
agonists are used primarily for the treatment of systemic hypertension. Their
efficacy as antihypertensive agents is somewhat surprising, since
many blood vessels contain postsynaptic 2 adrenergic
receptors that promote vasoconstriction (see Chapter 6). Indeed, clonidine,
the prototypic 2 agonist, was initially
developed as a vasoconstricting nasal decongestant. Its capacity
to lower blood pressure results from activation of 2 receptors
in the cardiovascular control centers of the CNS; such activation
suppresses the outflow of sympathetic nervous system activity from
the brain. Clonidine, an imidazoline, was synthesized in the early 1960s
and found to produce vasoconstriction that was mediated by receptors.
During clinical testing of the drug as a topical nasal decongestant,
clonidine was found to cause hypotension, sedation, and bradycardia.
The structural..."
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