What is midodrine, and how does it work?
Midodrine is an oral prodrug of an active metabolite (desglymidodrine). After absorption, it is converted in the body to desglymidodrine, which activates alpha-1 adrenergic receptors on vascular smooth muscle. This alpha-1 stimulation causes vasoconstriction, which raises peripheral vascular resistance and increases blood pressure.
What is its pharmacologic effect on blood pressure?
By promoting alpha-1–mediated vasoconstriction, midodrine increases both standing and overall blood pressure, helping counter the low blood pressure seen with conditions such as orthostatic hypotension (a drop in blood pressure when moving from lying/sitting to standing).
How does it differ from taking an alpha-1 agonist directly?
Because midodrine is a prodrug, it does not immediately provide the alpha-1 agonist effect. The conversion to desglymidodrine is required first, which then produces the vasoconstrictive (alpha-1) activity that drives the blood-pressure increase.
What mechanism explains its side effects (by receptor action)?
The same alpha-1–driven vasoconstriction that increases blood pressure can also contribute to typical effects associated with increased vascular tone, such as cold extremities or other symptoms related to altered blood flow and blood pressure regulation.
Quick take: the one-line mechanism
Midodrine works by converting to desglymidodrine, which activates alpha-1 adrenergic receptors to cause vasoconstriction and raise blood pressure.