High doses of the drug appeared to increase follicle diameter and reduce hair shedding.
Minoxidil appears to reverse hair follicle miniaturisation and increase follicle diameter, but only at higher doses than Regaine, new research suggests.
The findings run counter to early literature suggesting minoxidil didn’t help miniaturisation.
“That meant that the maximum efficacy was [thought to be] achieved at about six to 12 months, and thereafter, patients didn’t get any continued improvement,” said Professor Rod Sinclair, dermatologist and professor of medicine at the University of Melbourne.
“Which meant that as soon as you stopped it, you were back to square one with no benefit for the time that you’ve been on it.”
But a study by Professor Sinclair and colleagues on 33 patients with male androgenetic alopecia suggests otherwise.
“Now, what we shown is that it can reverse the miniaturisation and it can lead to an increase in fibre diameter, but it only does so at doses higher than what you would achieve with Regaine,” he said.
For lower doses, hair follicles continue to miniaturise.
Professor Sinclair and his colleagues analysed serial tattoo-localised phototrichograms with hair-to-hair matching software of participants randomly assigned to take either 0.45mg sublingual minoxidil or placebo for 24 weeks.
They then followed this double-blinded study with a further 24 week open-label extension trial on 12 of the previously placebo group participants, assigning them a once-daily dose of either 1.35mg or 4.05mg sublingual minoxidil.
At 24 weeks, the fibre diameter of men who took placebo had dropped by 2µm, particularly in fibres with an intermediate diameter of 40-60µm at baseline. Participants in the 0.45mg dose group also saw a 2µm drop in diameter.
In contrast, men who received the 1.35mg dose saw an increased diameter of 3µm and those taking the 4.05mg dose had an increased diameter of 6µm after 24 weeks of treatment. Likewise, the most increase was in intermediate and thick fibres.
“Not all patients will tolerate the higher dose, but many patients will,” Professor Sinclair said.
“That allows you to gradually increase the dose to the point where they’re getting maximum hair growth and still tolerating it.”
It was vital for patients to have more options for hair loss, Professor Sinclair said, adding that the current market for treatments was estimated to be around $10 billion per year.
He said phase 3 clinical trials were starting in Melbourne to test sublingual minoxidil in men at a higher dose of 5mg per day.
There are limited pharmacies that compounded sublingual minoxidil, partly because it’s a formulation patented by Professor Sinclair. And it was yet unclear how higher dose oral minoxidil compared with the sublingual formulation, he said.
One argument was that as soon as men stop using the product, all the hair they’d grown during treatment would fall out.
“With the with the sublingual minoxidil, we haven’t actually seen that,” he said.
“Sure, you start to lose hair again, but you tend to hang on to the hair that you’ve regrown.”
“It’s a bit like two cars slowly rolling down the hill, and the minoxidil car is being driven in reverse back up the hill, while the other car just continues to roll down the hill.
“If, in five years’ time, you decide you’ve had enough and you want to shave your head and go bald, then you can stop the tablet and the car will start to roll down the hill again. But you’ll never catch up to the first car, because you’ll always get the benefit for the time that you’ve been on the treatment.”
He likened it to hypertension medication, where blood pressure will start to increase again if a patient stops taking it, but the heart risks won’t be the same as never taking it because a patient has had all that time with good blood pressure.
