Can midodrine (proamatine) cause bradycardia (abnormally slow heart rate)?

Midodrine and Heart Rate Effects

Yes, midodrine can cause bradycardia (slow heart rate) through a reflex mechanism—when it raises blood pressure by constricting blood vessels, baroreceptors detect this increase and trigger vagal stimulation that slows the heart rate. 1

Mechanism of Bradycardia

• Midodrine works as an alpha-1 adrenergic agonist that increases peripheral vascular resistance and blood pressure through arterial and venous constriction 1
• The resulting blood pressure elevation activates arterial baroreceptors, which respond by increasing parasympathetic (vagal) tone to the heart 1
• This reflex vagal stimulation directly slows heart rate as a compensatory mechanism to the increased afterload 1
• The FDA label explicitly states that "a slight slowing of the heart rate may occur after administration of midodrine, primarily due to vagal reflex" 2

Clinical Significance and Monitoring

• Bradycardia is listed as a recognized side effect of midodrine therapy 1
• In a large retrospective ICU study of 1,119 patients, asymptomatic bradycardia (heart rate <50 beats/min, median 39 beats/min) was the most common side effect, occurring in 172 patients 3
• Patients should be monitored for symptoms suggesting bradycardia including pulse slowing, increased dizziness, syncope, or cardiac awareness 2
• The FDA recommends discontinuing midodrine if patients experience signs or symptoms of bradycardia 2

High-Risk Situations Requiring Caution

• Co-administration with negative chronotropic agents (beta-blockers, non-dihydropyridine calcium channel blockers, cardiac glycosides like digoxin) requires extreme caution due to additive heart rate reduction 1, 4
• Cardiac glycosides may enhance or precipitate bradycardia, AV block, or arrhythmias when combined with midodrine 2
• Hemodialysis patients warrant particular attention for bradycardia monitoring due to their unique hemodynamic vulnerabilities 1, 4
• In overdose situations, severe hypertension with reflex bradycardia (heart rate 43-60 bpm) has been documented 5

Common Pitfall to Avoid

• Do not assume bradycardia from midodrine indicates drug failure—it is an expected pharmacologic consequence of effective blood pressure elevation, not a contraindication to continued use unless symptomatic 1
• However, symptomatic bradycardia (causing dizziness, syncope, or hemodynamic compromise) requires immediate discontinuation and re-evaluation 2