Midodrine

Midodrine, sold under the brand name Proamatine among others, is an antihypotensive medication used to treat orthostatic hypotension (low blood pressure when standing) and urinary incontinence. It is taken by mouth.

Side effects of midodrine include hypertension (high blood pressure), paresthesia, itching (pruritus), goose bumps, chills, urinary urgency, urinary retention, and urinary frequency. Midodrine is a prodrug of its active metabolite desglymidodrine. This metabolite acts as a selective agonist of the α₁-adrenergic receptor. This in turn results in vasoconstriction and increased blood pressure.

Midodrine was discovered by 1971 and was introduced for medical use in the United States in 1996.

Midodrine is indicated for the treatment of symptomatic orthostatic hypotension. It can reduce dizziness and faints by about a third, but can be limited by troublesome goose bumps, skin itch, gastrointestinal discomfort, chills, elevated blood pressure while lying down, and urinary retention. A meta-analysis of clinical trials of midodrine or droxidopa in patients with low blood pressure when standing found that midodrine increased standing blood pressure more than droxidopa but that midodrine but not droxidopa increased the risk of high blood pressure when lying down. Small studies have also shown that midodrine can be used to prevent excessive drops in blood pressure in people requiring dialysis.

Midodrine has been used in the complications of cirrhosis. It is also used with octreotide for hepatorenal syndrome; the proposed mechanism is constriction of splanchnic vessels and dilation of renal vasculature. Studies have not been sufficiently well conducted to show a clear place for midodrine.

Midodrine is used off-label to increase blood pressure in the treatment of postural orthostatic tachycardia syndrome (POTS) where increased transduction of venous alpha 1 adrenergic receptors increases venous return.

Midodrine is available in the form of 2.5, 5, and 10 mg oral tablets.

Midodrine is contraindicated in people with severe organic heart disease, acute kidney disease, urinary retention, pheochromocytoma or thyrotoxicosis.