The pharmacological response with tilt-table testing predicts long-term efficacy in
neurocardiogenic syncope. However, beta-blockers for
neurocardiogenic syncope are often not tolerated or are ineffective. Since
cholinergic tone is important in the efferent part of the neurocardiogenic reflex, we investigated the pharmacodynamics and efficacy of
propantheline bromide in preventing
neurocardiogenic syncope. We studied 16 patients (11 males) with a mean age of 48.8 (+/- 15.1) years with
presyncope or
syncope and who had positive baseline tilt-table studies at a mean of 15.8 (+/- 10.3) minutes into the upright 60 degrees tilt. They were given
propantheline bromide orally, an
anticholinergic agent, at a dose of 64.3 (+/- 21.8) mg/day for 7 days, and tilt-table testing was repeated 1 hour after readministration of
propantheline bromide, 30 mg orally. After
propantheline bromide treatment, 13 of 16 patients (81%) had no inducible
presyncope or
syncope on repeat tilt-table testing. In this group of responders, the mean minimum heart rate during upright tilt-table testing increased from 43.2 (+/- 77.3) beats/min to 77.3 (+/- 17.2) beats/min after
propantheline bromide (p < 0.005). More significantly, the minimum mean arterial blood pressure increased from 42.2 (+/- 25) mmHg to 81.3 (+/- 16.7) mmHg (p < 0.0005) during upright tilt. At a follow-up of 15.2 (+/- 7.4) months, in the responder group (12 patients with long-term follow-up), the average dose of
propantheline bromide was 32.5 (+/- 23.8) mg/day, which was significantly reduced from the initial dose (p < 0.05). A clinical recurrence of symptoms occurred in only 4 out of 12 patients on
propantheline bromide (33%), none of which were directly attributable to
drug failure. It was concluded from this study that
propantheline bromide is highly effective in preventing
neurocardiogenic syncope. In addition,
propantheline bromide's effectiveness is more than would be expected by prevention of cardioinhibition in
neurocardiogenic syncope and would support a role for direct
cholinergic control of vascular tone.