Treatment Science · K-ATP channel opener · Discontinued antihypertensive
Pinacidil
the forgotten drug that grows hair
Pinacidil, minoxidil, and diazoxide are three blood-pressure drugs from three unrelated chemical families, and all three grow hair. The thing they share is not blood flow. It is a molecular gate called the ATP-sensitive potassium channel. Two clean experiments show the follicle is responding to the open channel, not to circulation.
- One channel, three unrelated drugs: minoxidil, pinacidil, and diazoxide come from three different chemical families and share almost nothing except that each pries open the same ATP-sensitive potassium channel, and each grows hair (Buhl 1992).
- Minoxidil's own maker found a molecule that beat it: in 1992 Upjohn tested the class on balding macaques, and a pinacidil analog called P-1075 grew more hair than minoxidil at the same concentration (Buhl 1992).
- The channel, not the blood flow: hydralazine raises blood flow but does not open the channel and grows no hair; a channel opener too selective to dilate a vessel still grew hair in a dish with zero circulation (Davies 2005).
Evidence synthesis · potassium-channel-opener pharmacology and the primate + isolated-follicle literature · Last reviewed July 2026
1989
year pinacidil was FDA-approved for hypertension
then outclassed by ACE inhibitors and calcium channel blockers, and discontinued
3 families
unrelated chemical classes
minoxidil (pyrimidine), pinacidil (cyanoguanidine), diazoxide (benzothiadiazine), all K-ATP openers, all grow hair
P-1075
pinacidil analog that grew more hair than minoxidil
in Upjohn's own balding-macaque study (Buhl 1992)
0 circulation
a selective opener grew hair in isolated follicles in a dish
no blood supply exists in culture, so vasodilation is excluded (Davies 2005)
Overview
A forgotten drug with a strange side effect
Pinacidil was a 1980s blood-pressure pill, a peripheral vasodilator that lowers pressure by opening ATP-sensitive potassium channels in the walls of blood vessels. It was FDA-approved in 1989, then quickly outclassed by better-tolerated ACE inhibitors and calcium channel blockers, and it was discontinued. Direct vasodilators like pinacidil tend to cause fluid retention and reflex fast heartbeat, which made it a hard sell against the newer classes.
On the way out, it did something strange. It grew hair, on the face, arms, and back. If that sounds familiar, it should. Pinacidil is the third member of a small and unlikely club: three blood-pressure drugs, from three unrelated chemical families, that all grow hair. This page is about what that coincidence is trying to tell us.
The class effect
One channel, three unrelated drugs
Minoxidil, pinacidil, and diazoxide do not look alike. Minoxidil is a pyrimidine, pinacidil a cyanoguanidine, diazoxide a benzothiadiazine. On a chemist's bench they are three different molecules built for the same job of lowering blood pressure. The one property they share is that each pries open the ATP-sensitive potassium channel, and each, as an unintended effect, grows hair (Buhl 1992).
The human potency differs sharply between them, which is exactly what you would expect from three different keys fitting the same lock with different efficiency. That variation is the point: hair growth tracks the shared mechanism, not the shared chemistry, because there is barely any shared chemistry to track.
Three chemical families, one shared mechanism
| Drug | Chemical family | Built for | Reported excess hair growth |
|---|---|---|---|
| Minoxidil | Pyrimidine | Hypertension (now hair loss) | 80-100% of adults on the oral drug |
| Pinacidil | Cyanoguanidine | Hypertension (discontinued) | roughly 2-13% |
| Diazoxide | Benzothiadiazine | Hypertension / low blood sugar | about 45% in hyperinsulinism patients (Yang 2021) |
Rates come from different populations and formulations and are not directly comparable; the point is that all three drugs cause excess hair growth often enough to be a recognized effect, not a fluke.
The Upjohn result
Minoxidil's own maker found a molecule that beat it
The most striking piece of evidence came from the last place you would expect. In 1992, Upjohn, the company that made minoxidil, tested the whole potassium-channel-opener class on balding stumptailed macaques, the same primate model that helped validate both minoxidil and finasteride. They ran their own drug against a pinacidil analog called P-1075.
The pinacidil cousin grew more hair than minoxidil at the same concentration (Buhl 1992). In the same body of work, these openers stimulated the molecular signature of hair-follicle cells getting ready to divide in culture, which told the authors the drugs act on the follicle directly rather than through the bloodstream.
The result that reframes the whole class
Minoxidil's own maker, testing on balding monkeys, found that a pinacidil analog grew more hair than minoxidil at the same dose (Buhl 1992).
P-1075 is a pinacidil analog, not pinacidil itself. The point is the mechanism: a molecule from a completely different family, opening the same channel, matched and beat the blockbuster.
Channel vs blood flow
The experiment that ends the blood-flow debate
The popular story is that minoxidil grows hair by increasing blood flow to the scalp. Two experiments, run in opposite directions, take that explanation apart.
First, block one and keep the other. Hydralazine is a direct vasodilator used for the same stubborn high blood pressure as minoxidil. It raises blood flow just as well, but it does not open the ATP-sensitive potassium channel, and in decades of use it has never grown hair. Now flip it. NNC 55-0118 is a potassium-channel opener built so selectively for the pancreatic channel that it cannot dilate a blood vessel at all. Dropped onto isolated follicles in a dish, with zero circulation, it grew hair anyway (Davies 2005). In the same assay, a channel-blocking sulfonylurea abolished the growth, which is the clean fingerprint that the effect runs through the channel.
Blood flow without the channel does nothing. The channel without blood flow grows hair. That is a clean double dissociation: the follicle is not responding to circulation, it is responding to an open potassium channel.
The everyday proof
Half your medicine cabinet raises blood flow. None of it grows hair.
If blood flow grew hair, the most-prescribed drugs on earth would be hair drugs. They are not. Amlodipine, lisinopril, and losartan are taken by hundreds of millions of people, all of them boosting blood flow, and none grows hair. A few even shed it.
Sildenafil goes further than a simple vasodilator: it floods tissue with blood and raises VEGF right around the follicle, which is the exact story people tell about minoxidil. It is still not a hair drug. The dividing line is not how much blood a drug moves. It is whether the drug opens one specific gate.
Blood-flow drugs vs the channel
| Drug | Class | Raises blood flow | Grows hair |
|---|---|---|---|
| Amlodipine | Calcium channel blocker | Yes | No |
| Lisinopril | ACE inhibitor | Yes | No (rare shedding) |
| Losartan | ARB | Yes | No |
| Sildenafil | PDE5 inhibitor | Yes, plus perifollicular VEGF | No |
| Hydralazine | Direct vasodilator | Yes | No |
| Minoxidil | Vasodilator and K-ATP opener | Yes | Yes |
The only entry that grows hair is the only one that opens the ATP-sensitive potassium channel.
What we are testing
The settled question, and the open one
The settled question is whether opening ATP-sensitive potassium channels grows hair. Three unrelated drugs, a primate study, and an isolated-follicle experiment already answered it. The class effect is not seriously in doubt.
The open question is what happens downstream, inside the follicle, once the channel is open. Which cells respond, which genes switch on, and how that program drives a follicle from rest into growth are not yet mapped. An honest caveat belongs here too: even minoxidil's mechanism is not fully closed, and at least one study argued part of its benefit may be vascular rather than a pure channel effect. The K-ATP story is the leading explanation, not the final word.
That downstream program is exactly what we are building our model to test: isolated human follicles, a selective non-vasodilating opener as the key test arm, a vasodilator that does not open the channel as the negative control, and a channel blocker to confirm the signal runs through the gate.
Frequently asked questions
Pinacidil, answered straight
Why was pinacidil discontinued?
Pinacidil was FDA-approved for high blood pressure in 1989 and then outclassed by better-tolerated drug classes, chiefly ACE inhibitors and calcium channel blockers. As a direct vasodilator it tended to cause fluid retention and a reflex fast heartbeat, which made chronic use unattractive once gentler options existed. Its withdrawal is best understood as a tolerability and commercial decision, not a formal FDA safety withdrawal.
Does pinacidil grow hair?
Pinacidil caused excess hair growth (hypertrichosis) as a side effect when used for blood pressure, on the order of a few to about 13% of patients, and pinacidil stimulated hair-follicle cells in the laboratory. In Upjohn's balding-macaque study a pinacidil analog, P-1075, actually grew more hair than minoxidil at the same concentration (Buhl 1992). It has never been tested or developed as a human hair-loss treatment.
How is pinacidil related to minoxidil?
They are different molecules from different chemical families, pinacidil a cyanoguanidine and minoxidil a pyrimidine, that share one mechanism: both open ATP-sensitive potassium channels. That shared mechanism, not any shared chemistry, is why both lower blood pressure and both grow hair.
Is it the potassium channel or the blood flow that grows hair?
The evidence points to the channel. Hydralazine raises blood flow but does not open the channel and grows no hair, while NNC 55-0118, an opener too selective to dilate a blood vessel, grew hair in isolated follicles in a dish with no circulation at all (Davies 2005). Blood flow without the channel does nothing; the channel without blood flow grows hair.
If blood-flow drugs grew hair, wouldn't common ones do it?
That is exactly the tell. Amlodipine, lisinopril, losartan, and sildenafil all raise blood flow and are taken by hundreds of millions of people, and none is a hair drug. Sildenafil even raises VEGF around the follicle and still does nothing for hair. The dividing line is opening one specific potassium channel, not moving blood.
Can you use pinacidil for hair loss?
No. Pinacidil is a discontinued blood-pressure drug with no approved or studied use for pattern hair loss and no human hair-loss trial behind it. It is discussed here as evidence that the potassium channel is a real target, not as a treatment. Anagen does not sell or compound pinacidil for hair loss.
Limitations
What this page can and cannot support
The class effect is well supported, but pinacidil itself has almost no direct human hair data. These constraints bound every claim above.
01
There is no human hair-loss trial of pinacidil. Its entire human hair record is hypertrichosis observed while treating blood pressure, plus laboratory follicle data.
02
P-1075 is a pinacidil analog, not pinacidil. The monkey result that beat minoxidil used the analog; pinacidil itself was not the tested molecule in that arm (Buhl 1992).
03
The double-dissociation evidence is preclinical. NNC 55-0118 grew hair in isolated follicle culture, not in a human scalp trial (Davies 2005).
04
Hair-growth rates across the three drugs come from different populations and formulations and are not directly comparable.
05
Even minoxidil's mechanism is not fully settled. At least one study argued part of its benefit may be vascular rather than a pure channel effect, so the K-ATP story is the leading explanation, not a closed case.
06
The downstream follicular program is unmapped. Which genes and cells respond to an open channel is the open question, which is what our model is built to test.
Sources & citations
Every claim, traced to its source
The primary literature behind the class effect, the Upjohn primate result, and the channel-versus-blood-flow experiments above.
- 1Buhl AE, Waldon DJ, Baker CA, Johnson GA Potassium channel conductance: a mechanism affecting hair growth both in vitro and in vivo. PMID 1545141doi:10.1111/1523-1747.ep12499788
- 2Davies GC, Thornton MJ, Jenner TJ, et al. Novel and established potassium channel openers stimulate hair growth in vitro: implications for their modes of action in hair follicles. PMID 15816824doi:10.1111/j.0022-202X.2005.23643.x
- 3Shorter K, Farjo NP, Picksley SM, et al. Human hair follicles contain two forms of ATP-sensitive potassium channels, only one of which is sensitive to minoxidil. PMID 18258787doi:10.1096/fj.07-099424
- 4Nakaya Y, Hamaoka H, Kato S, et al. Effect of minoxidil sulfate and pinacidil on single potassium channel current in cultured human outer root sheath cells. PMID 7947101doi:10.1016/0923-1811(94)90041-8
- 5Yang H, et al. Efficacy and safety of diazoxide for treating hyperinsulinemic hypoglycemia: a systematic review and meta-analysis. PMID 33556119doi:10.1371/journal.pone.0246463
- 6DrugBank Pinacidil (DB06762): ATP-sensitive potassium channel opener, antihypertensive. https://go.drugbank.com/drugs/DB06762
The K-ATP opener you can actually use
The one channel opener with human hair data
Pinacidil is a discontinued drug used here to illustrate the mechanism. Minoxidil is the potassium-channel opener with published human hair results and a real formulation. It is used off-label for hair loss and is not FDA-approved for that use in oral form; a licensed clinician decides whether it is appropriate for you, and individual results vary.
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