Key result
In patients with autonomic dysfunction, the blood pressure response to clonidine was inversely proportional to supine norepinephrine levels, while yohimbine raised blood pressure and attenuated the hypotensive response to head-up tilt by 50%.
Why the study?
Do clonidine and yohimbine alter blood pressure and plasma catecholamines in patients with autonomic dysfunction?
Do clonidine and yohimbine alter blood pressure and plasma catecholamines in patients with autonomic dysfunction?
p-value: p=<0.05
Yohimbine and clonidine can be used as pharmacological probes to assess residual sympathetic tone in patients with autonomic dysfunction, with yohimbine showing potential therapeutic benefit for orthostatic hypotension.
May inform sympathetic tone assessment in autonomic dysfunction; leaves open yohimbine's therapeutic role pending controlled trials.
We studied the effects of clonidine, an alpha 2-adrenoreceptor agonist, and yohimbine, an alpha 2-adrenoreceptor antagonist, on blood pressure, heart rate, and plasma catecholamines in 12 patients with autonomic dysfunction. Clonidine (0.1 mg, orally) lowered blood pressure 18 +/- 3 torr in six subjects and raised it 5 +/- 1 torr in six. The change in blood pressure in response to this dose of clonidine was inversely proportional to the supine level of norepinephrine (P less than 0.05). Yohimbine (4-64 micrograms/kg) raised plasma norepinephrine and blood pressure in six patients with degenerative autonomic dysfunction. Yohimbine also attenuated by 50% (P less than 0.05) the hypotensive response to head-up tilt of patients with degenerative autonomic dysfunction. Clonidine depends upon postjunctional hypersensitivity and the degree of autonomic insufficiency to elicit its pressor response. In contrast, the pressor response to yohimbine is related to the capacity of the sympathetic nervous system to be activated and release norepinephrine. If plasma norepinephrine levels following yohimbine administration are monitored, the biochemical and hemodynamic response to the drug may provide a sensitive indication of the capacity of the sympathetic nervous system to be activated in patients with autonomic dysfunction.
No takes yet. Share an insight, caveat, or question.
Robertson et al. (1986) studied Autonomic dysfunction (n=12). Clonidine and Yohimbine vs. Baseline was evaluated on Change in blood pressure in response to clonidine and its correlation with supine norepinephrine (p=<0.05). In patients with autonomic dysfunction, the blood pressure response to clonidine was inversely proportional to supine norepinephrine levels, while yohimbine raised blood pressure and attenuated the hypotensive response to head-up tilt by 50%.
Synapse has enriched 2 closely related papers on similar clinical questions. Consider them for comparative context: