title: Comparative efficacy of yohimbine against pyridostigmine for the treatment of orthostatic hypotension in autonomic failure.
abstract: Orthostatic hypotension affects patients with autonomic failure producing considerable disability because of presyncopal symptoms. Severely affected patients may have residual sympathetic tone that can be engaged to increase blood pressure (BP) with the α-2 adrenergic antagonist yohimbine. This medication activates sympathetic outflow centrally and unrestrains norepinephrine release from noradrenergic neurons. Alternatively, the acetylcholinesterase inhibitor, pyridostigmine, can increase sympathetic tone by improving ganglionic cholinergic neurotransmission. Our purpose was to compare these complementary approaches and to explore whether the combination would lead to synergistic increases in BP. We compared the effects of 60 mg of pyridostigmine and 5.4 mg of yohimbine in a single-blind, randomized, placebo-controlled, crossover fashion. In a subset of patients we tested the combination of pyridostigmine and yohimbine. Our primary outcome was the change in standing diastolic BP 60 minutes after drug administration from baseline. We studied a total of 31 patients with severe autonomic failure. Yohimbine significantly improved standing diastolic BP as compared with placebo (11±3 mm Hg [95% CI: 6 to 16 mm Hg]; P<0.001). On the contrary, pyridostigmine did not increase the standing diastolic BP (0.6±3 mm Hg [95% CI: -5 to 5 mm Hg]; P=0.823). Only yohimbine showed a significant improvement in presyncopal symptoms. Sixteen patients received the combination of pyridostigmine and yohimbine, but no evidence of synergistic pressor effect was found. Engaging residual sympathetic tone with yohimbine is a more effective approach to improve orthostatic hypotension as compared with pyridostigmine in patients with severe orthostatic hypotension.
authors.affiliation: Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tenn, USA.
authors.forename: Cyndya
authors.initials: C
authors.lastname: Shibao
authors.forename: Luis E
authors.initials: LE
authors.lastname: Okamoto
authors.forename: Alfredo
authors.initials: A
authors.lastname: Gamboa
authors.forename: Chang
authors.initials: C
authors.lastname: Yu
authors.forename: Andre'
authors.initials: A
authors.lastname: Diedrich
authors.forename: Satish R
authors.initials: SR
authors.lastname: Raj
authors.forename: David
authors.initials: D
authors.lastname: Robertson
authors.forename: Italo
authors.initials: I
authors.lastname: Biaggioni
mesh_terms: D000317:Adrenergic alpha-Antagonists / Q000627:therapeutic use; D000368:Aged; D000704:Analysis of Variance; D001794:Blood Pressure / Q000187:drug effects*; D002800:Cholinesterase Inhibitors / Q000627:therapeutic use; D018592:Cross-Over Studies; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D007024:Hypotension, Orthostatic / Q000150:complications / Q000188:drug therapy* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D054970:Pure Autonomic Failure / Q000150:complications* / Q000503:physiopathology; D011729:Pyridostigmine Bromide / Q000627:therapeutic use*; D016037:Single-Blind Method; D015016:Yohimbine / Q000627:therapeutic use*
chemical_list: D000317:Adrenergic alpha-Antagonists; D002800:Cholinesterase Inhibitors; D015016:Yohimbine; D011729:Pyridostigmine Bromide