Midodrine Dosing Schedule
Midodrine should be administered during daytime hours only, with the last dose taken no later than 6 PM and at least 4 hours before bedtime to prevent supine hypertension during sleep. 1
Recommended Dosing Schedule
The FDA-approved dosing schedule for midodrine is:
- Standard dose: 10 mg, 3 times daily 1
- Recommended timing:
- First dose: Shortly before or upon arising in the morning
- Second dose: Midday
- Third dose: Late afternoon (not later than 6 PM)
This schedule maintains approximately 4-hour intervals between doses, which aligns with the medication's pharmacokinetics, as the half-life of desglymidodrine (the active metabolite) is approximately 4 hours 2.
Rationale for Timing Restrictions
The timing restrictions for midodrine administration are critical for patient safety:
Supine Hypertension Prevention: Midodrine causes vasoconstriction that can lead to dangerous elevations in blood pressure when the patient is lying down 1.
Matching Activity Levels: The medication should be taken when the patient needs to be upright and pursuing daily activities, as it's specifically indicated for orthostatic hypotension 1.
Special Dosing Considerations
In patients with renal impairment, a lower starting dose of 2.5 mg is recommended due to renal excretion of desglymidodrine 1.
Doses may be given at 3-hour intervals if required to control symptoms, but not more frequently 1.
While single doses as high as 20 mg have been given to patients, these higher doses are associated with a high rate (about 45%) of severe and persistent supine hypertension 1.
Monitoring Requirements
Regular monitoring of blood pressure in both supine and standing positions is essential 1.
The administration of midodrine should be discontinued if supine blood pressure increases excessively 1.
Patients should report symptoms of supine hypertension immediately, including cardiac awareness, pounding in the ears, headache, and blurred vision 1.
Common Pitfalls to Avoid
Evening/Nighttime Dosing: Never administer midodrine after the evening meal or less than 4 hours before bedtime due to the risk of supine hypertension during sleep 1.
Urologic Effects: Be aware that midodrine can cause urinary retention, particularly in patients with spinal cord injury who void urine spontaneously, due to its alpha-1-adrenergic effects on the bladder neck 1, 3.
Drug Interactions: Use caution when midodrine is administered concomitantly with other vasoconstrictors, cardiac glycosides, or medications that reduce heart rate 1.
By following these timing guidelines, the effectiveness of midodrine in treating orthostatic hypotension can be maximized while minimizing the risk of serious adverse effects, particularly supine hypertension.