Serotonin reuptake inhibitor (Paxil) does not prevent the vasovagal reaction associated with carotid sinus massage and/or lower body negative pressure in healthy volunteers.
BACKGROUND
The purpose of this study was to assess the effect of the serotonin reuptake inhibitor paroxetine hydrochloride (Paxil, SmithKline Beecham) on cardiovascular reflexes. We hypothesized that Paxil prevents neurally mediated syncope (NMS) by attenuating the sympathoinhibition and vagotonia associated with a vasovagal reaction.


RESULTS
In a double-blind randomized study, 25 healthy subjects with a positive response to either carotid sinus massage (CSM) or lower body negative pressure (LBNP) received Paxil (20 mg/d) or placebo for 6 weeks. Arterial baroreflex sensitivity (BRS), muscle sympathetic nerve activity (SNA), baroreflex control of SNA, blood pressure, and heart rate responses to CSM and LBNP were measured at baseline and at 6 weeks. Nineteen subjects completed the study (Paxil, n=9; placebo, n=10). In the Paxil group, BRS decreased significantly compared with baseline (15.8+/-4.0 ms/mm Hg versus 11.0+/-2.6 ms/mm Hg, P=0.05); however, all 9 subjects continued to have a positive response to LBNP with presyncope. Paxil did not attenuate the sympathoinhibition or vagotonia associated with a positive LBNP response and had no significant effect on baroreflex control of SNA. In the control group, no significant change in BRS was noted compared with baseline. Seven out of 9 subjects who had a positive LBNP response at baseline had a repeat positive LBNP response, and the subject with a positive CSM at baseline had a negative response at 6 weeks.


CONCLUSIONS
Paxil decreases arterial BRS but does not prevent the presyncope associated with LBNP. The effect of Paxil on the autonomic reflexes in patients with neurally mediated syncope remains unclear.
Takata
Theodore S
TS
University of Texas Southwestern Medical Center and Dallas Veterans Affairs Medical Center, Dallas, Tex 75390-9047, USA.
Wasmund
Stephen L
SL
Smith
Michael L
ML
Li
Jian-Ming
JM
Joglar
Jose A
JA
Banks
Kim
K
Kowal
Robert C
RC
Page
Richard L
RL
Hamdan
Mohamed H
MH
D000818:Animals; D017704:Baroreflex / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects; D002346:Carotid Sinus; D002415:Cats; D004311:Double-Blind Method; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D008150:Lower Body Negative Pressure / Q000009:adverse effects*; D008297:Male; D008405:Massage / Q000009:adverse effects*; D017374:Paroxetine / Q000494:pharmacology*; D051381:Rats; D017367:Selective Serotonin Reuptake Inhibitors / Q000494:pharmacology*; D013564:Sympathetic Nervous System / Q000187:drug effects; D019462:Syncope, Vasovagal / Q000209:etiology / Q000517:prevention & control*
D017374:Paroxetine; D017367:Selective Serotonin Reuptake Inhibitors