KATP opener (vascular)
Vascular smooth-muscle KATP channel opener (Kir6.1/SUR2B)
- Hyperpolarizes vascular smooth muscle → arteriolar dilation
- Arteriolar, not venous → little postural hypotension
- Reflex tachycardia; sodium and water retention
- Opens Kir6.1/SUR2B KATP channels in vascular smooth muscle → hyperpolarization closes L-type calcium channels → arterioles dilate
- Arteriolar, not venous: preload is preserved, so postural hypotension is uncommon
- Reflex tachycardia and avid sodium retention follow, which is why oral minoxidil is given with a beta blocker and a loop diuretic
Drugs with this mechanism (3)
- Diazoxide — KATP channel OPENER that shuts off insulin release; the mirror image of a sulfonylurea.
- Minoxidil oral — Potent vasodilator; the hair-growth side effect became its main use.
- Minoxidil topical — Topical potassium-channel opener for androgenetic hair loss; benefit requires continued use.
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