Why Rogaine solution works better, and some thoughts on making it work better still

[Energizer]

It seems to be fairly well known that Rogaine/minoxidil solution is more effective than Rogaine foam.

Why?

As many have said, it is because of the mechanism of penetration into the hair cell. But more specifically, what mechanism? I have some thoughts. Someone with formal training in chemistry and biology should be able to hone them more.

There are two barriers to effective penetration of the follicle shaft and absorption at the root: surface tension, and sebum.


Surface tension

If we were to dissolve minoxidil in plain old water, not very much of it would get to the follicles that need it most. Water has a high contact angle, and fairly high surface tension so that it has a tendency to stick together and resist whetting of many surfaces.

If you were to pour out a small glass of water over a completely flat surface, it would spread itself out and pool naturally over an area, but at a certain point stop. This is the equilibrium at which gravity, the surface tension of water, and the characteristics of the surface hold the pool in the same shape. Now, if you were to poke a small hole in the surface, water would not start pouring through, even though the molecules are, obviously, much smaller than the hole. You could keep enlarging the hole and water would start to bulge downwards into the hole. Enlarge the hole just a little more and the water starts to drop through.

As a practical example, take a window screen, turn it horizontal, and put some water on the screen and see what happens. Some droplets will skitter across the top without falling through the holes, others will cling in between the wires creating the grid (which are themselves round). Repeat the experiment with oil. Droplets do not form at all, and just about all the oil oozes through the holes. Some of it sticks to the wires, but there are no films of oil spreading across from one wire to the next.

The scalp, with its many follicles, is not unlike the window screen. Spread a film of liquid with high surface tension over the top, and that liquid will have difficulty penetrating the small holes. (For follicles in which there is a shaft protruding out of the follicle, there might be something called capillary action that will draw liquid down into the hole, but as we know many hairs miniaturized hairs are not protruding). Spread a liquid with low surface tension, and it will ooze into the holes, aided both by gravity and capillary flow.

Propylene Glycol and alcohol have less surface tension than water. Gravity has an easier time pulling the liquid into the follicle, and the liquid has an easier time being drawn into and whetting the follicle.

The foam is an aerosol with no propylene glycol. Theoretically, I guess the chemicals that make up the liquid in the aerosol may be able to make it into the follicle just as effectively as propylene glycol and ethanol, but there is so little of it gravity certainly won’t do the work, and capillary action will have a tough time, too. Once the foam is distributed and no longer visible, it will be the thickness of however thick each individual bubble within the aerosol was (just a few molecules thick) multiplied by the number of bubbles vertically. Hundreds? Thousands of layers? Perhaps, but probably no thicker than old fashioned rogaine solution, if you were to actually measure it.


Sebum.

Once the solution is inside the follicle, or as far down as it can go, it encounters another hurdle. It is still not in contact with the cell. It is separated by oil produced by the sebaceous gland, sebum. We all know that water and oil do not mix. In order to effectively deliver the medicine into the cell, it must first pass through the sebum barrier.

This is why propylene glycol and alcohol are essential, and the only other ingredients besides water, in Rogaine solution. Propylene glycol has a polarity similar to sebum, and is miscible in it. It is able to mix with the sebum and deliver the chemical across that final, oily barrier.

Alcohol also helps penetrate the sebum by dissolving it, but perhaps in a more severe, irritating way. I suspect it is also there to speed the drying of syrupy propylene glycol, and reduce the viscosity of the solution to make it easier to apply. Minoxidil is also much more soluble in alcohol than either PG or water, so the ethanol and propylene glycol probably team up to actually deliver the medicine.

Why there is water in the formulation, I don’t know.


Making minoxidil work even better

As this forum seems to be aware, just because something works medically does not mean it makes it to market.

I was thinking about these two barriers, sebum and surface tension, and how propylene glycol and ethanol, while effective, may not be *the* most effective solvents for delivering minoxidil. They are probably the most cost effective chemicals that could be medically approved.

To learn more about propylene glycol’s efficacy for penetrating sebum, I googled “propylene glycol sebum” and was immediately rewarded with this.

A patent for a novel minoxidil preparation using more exotic, but more effective, solvents and oils chosen to penetrate sebum and, I learned, the outermost layer of skin as well.

Abstract: “Novel topical formulations of minoxidil comprising minoxidil; a solvent for minoxidil; a non-polar solvent which renders the formulation approximately the same polarity as human sebum; and a cosolvent which enhances the delivery of minoxidil through the stratum corneum.”

The most interesting sentence in the patent: “Minoxidil is not well absorbed through the skin in the prior art formulations (e.g., propylene glycol/ethanol/water). Thus, addition of a vehicle component that enhances skin penetration as well as renders the silicone oils and propylene glycol miscible is desired.”

The formulation differs from off the shelf minoxidil in its use of oleyl alcohol, isopropanol, and a proprietary silicon oil called Dow Corning - 344 fluid. Some other stuff is mentioned too.

This patent seems to be abandoned, and who knows if any human trails were ever done. Maybe the formulation was extremely irritating, or disrupted the natural biota of the scalp. Or, maybe it is extremely effective but was never taken through the formalities of approval.

This recipe is something a very dedicated minoxidil user could mix up in his/her kitchen. I can’t help but wonder, if standard minoxidil solution is more effective than foam, if this recipe would be more effective than the standard solution.

Anyone want to give it a shot?

[ledhead]

Or some people lack the enzyme needed to convert minoxidil into minoxidil sulfate which stimulates hair growth..