From the Guidelines
Midodrine does not typically cause tachycardia, and in fact, it is more commonly associated with bradycardia as a side effect. According to the study published in Diabetes/Metabolism Research and Reviews 1, midodrine is a peripheral selective α1-adrenergic agonist that exerts a pressor effect through both arteriolar constriction and venoconstriction of the capacitance vessels. The study lists adverse events associated with midodrine, including pilomotor reactions, pruritus, supine hypertension, bradycardia, gastrointestinal symptoms, and urinary retention, but tachycardia is not mentioned.
The mechanism of action of midodrine involves stimulating alpha receptors in blood vessel walls, causing vasoconstriction, which increases peripheral resistance and raises blood pressure. When blood pressure increases due to midodrine, the body's natural baroreceptor reflex often responds by slowing the heart rate to maintain cardiovascular homeostasis. This is consistent with the observation that midodrine is more likely to cause bradycardia than tachycardia.
Key points to consider when prescribing midodrine include:
- The dosing should be individually tailored, up to two to four times 10 mg/day, with the first dose taken before arising and use avoided several hours before planned recumbency, particularly in patients with documented supine hypertension.
- Patients taking midodrine should avoid lying flat for 4 hours after taking a dose to prevent dangerous elevations in blood pressure while supine.
- Common side effects of midodrine include piloerection, scalp tingling, urinary retention, and supine hypertension, but tachycardia is not typically observed.
From the FDA Drug Label
The patient should be cautioned to report symptoms of supine hypertension immediately. Symptoms may include cardiac awareness, pounding in the ears, headache, blurred vision, etc. A slight slowing of the heart rate may occur after administration of midodrine, primarily due to vagal reflex Patients who experience any signs or symptoms suggesting bradycardia (pulse slowing, increased dizziness, syncope, cardiac awareness) should be advised to discontinue midodrine and should be re-evaluated.
Midodrine does not cause tachycardia, it may cause a slight slowing of the heart rate due to vagal reflex, which can lead to bradycardia in some patients 2.
From the Research
Midodrine and Tachycardia
- Midodrine is a peripheral alpha-adrenergic agonist used to treat orthostatic hypotension and secondary hypotensive disorders 3.
- Studies have shown that midodrine increases standing blood pressure and improves symptoms of orthostatism without associated cardiac stimulation 3, 4.
- However, one study found that heart rate increased after 5 to 10 mg doses of midodrine, with statistically significant increases at 120 minutes 5.
- Another study reported asymptomatic bradycardia (heart rate < 50 beats/min) as the most common side effect of midodrine, rather than tachycardia 6.
- Overall, the evidence suggests that midodrine may not typically cause tachycardia, but may have variable effects on heart rate depending on the individual and dosage 3, 4, 5, 6, 7.
Adverse Effects of Midodrine
- Common adverse effects of midodrine include piloerection, gastrointestinal disorders, and cardiovascular complaints, which are generally mild and can be controlled by reducing the dosage 3.
- Other reported side effects include supine hypertension, scalp pruritus/tingling, urinary urgency, and chills 4, 6, 7.
- Midodrine is generally well-tolerated, with most side effects being mild to moderate 3, 4, 7.