Yeddie said:
Bryan said:
The fact that 5% minoxidil is more effective than 2% minoxidil (at the standard doses that are used, of course) is indeed an empirical observation, but your EXPLANATION for that effect is not! IMHO, the effect is due simply to the greater amount of the drug which is deposited on your scalp, not the difference in the concentrations of the starting solutions (see below for further comments on that subject).
Bryan, you're wrong. You need to go get an independent opinion on this subject from somebody else, not me.
If you believe that 5% minoxidil is more effective more because a larger dose is applied to your scalp and less because of the increased concentration then you are simply wrong. And "No," I now don't believe you understand mass transport, but maybe you just decided to gloss over it for some reason.
Increased concentration of a topical drug is not a matter of theory, it is simply the way things work. I gave that example not to propose a theory but rather to try to illustrate the mechanism to you in a simplified format. It is also the way you breath (oxygen in and CO2 out) and the way nutrients pass into your bloodstream from your digestive tract and the way that toxins are removed by your liver and kidneys and the way that ALL chemicals enter your body through your skin etc. etc. etc. Partitioning coefficients, chemical potential, reactive transport mechanisms, electrical potential, equimolar diffusion, static potential, and Knudsen diffusion all play a part but I am mentioning these only for the sake of completeness.
I really respect your knowledge (I assume that you are indeed a chemist?) and I'm sure you know all the exquisite details of how molecules diffuse across membranes, but I still think you're assuming too much about the topical absorption of minoxidil. I think it's too complicated a process to assume that the concentration in the vehicle is the only thing that matters.
Here's a simple example of what I mean: have you read the chapter on hairloss in Durk Pearson & Sandy Shaw's book "Life Extension"? They describe the interesting therapy that Durk had been using, which consisted of dissolving estrogen and testosterone esters in DMSO and applying it to the scalp. Here's what they say at one point:
"The solvent used to deposit these hormone esters in the scalp must be low in toxicity, high in fat solvent power, able to rapidly penetrate the skin, and miscible (mutually soluble) with water. DMSO meets these requirements very well. The testosterone cypionate and estradiol dipropionate dissolve slowly in dry DMSO but precipitate out of solution when a small amount of water is added. This is exactly what happens when the solution is applied to your scalp. The DMSO carries the hormone esters through the dry waxy oily dead outer layer of skin. When it reaches the upper layer of living cells, however, their high water content causes the prompt precipitation of the hormone esters right where you want them. The DMSO soon spreads throughout your body, but most of the very hydrophobic hormone esters are left behind in the scalp where they belong."
Do you see my point? Using the technique above, are you going to maintain that you couldn't deposit the same amount of those hormones by using a larger amount of a lower concentration in that DMSO vehicle? How do you know that there isn't a similar confounding process going on when you apply Rogaine?
Yeddie said:
Bryan said:
2% Rogaine contains a lot more alchohol (and less propylene glycol) than 5% Rogaine. What do you think happens when you drop a milliliter of that stuff on your scalp? I'll tell you what happens: a lot of it (most of it?) quickly evaporates, causing the dissolved minoxidil to concentrate even more in the available PPG. In other words, whenever you use EITHER version, once the alcohol dries, you're left with a slurry of PPG with dissolved minoxidil sitting on your scalp, and it doesn't differ that much from one version to the other.
That's not the way an ethanol PPG solution would react. This is a transient evaporation of a binary solution (considering the minoxidil as non-vol) and one component will not evaporate entirely whilst another remains entirely.
No, but I think it WOULD react that way to a lesser extent, especially given enough time (which might be the whole quibble point in this issue). Have you read the studies on the absorption of topical minoxidil from verious vehicles consisting of different ratios of ethanol and propylene glycol (I believe they're still right here on this site, in full)? If I recall correctly, they also pointed out that the alcohol could evaporate from such a binary solvent system, concentrating the minoxidil in the remaining PPG.
Because I was curious about what you said, I did some little experiments of my own: I put a couple of mL of PPG (2.07 grams) and a couple mL of Everclear (1.62 grams) in a small beaker (total mixture: 3.69 grams). After a few minutes of vigorous stirring, the mix was down to 3.59 grams (evaporation of some of the alchohol, no doubt). Then I set the beaker down, uncovered, in a clean place at controlled room temperature. I _expected_ to find that after a period of time, the alcohol would evaporate, leaving just the 2.07 grams of PPG. But to my annoyance, after a couple of hours or so had gone by, the weight seemed to stabilize around the 2.52 gram level. But there was no more detectable odor of alcohol!
I realized what must be happening: PPG is hygroscopic enough that it must be drawing water out of the air! To test THAT theory, I put another couple of mL of PPG (1.94 grams) in another shallow, open container, and set it aside. After another similar period of a couple of hours or so, the weight had increased to 2.3 grams. It had absorbed almost 20% of its weight in water from the air, and that increase was about the same as the discrepancy that I had seen in the first Everclear/PPG mix, which explains the somewhat confounding result I got in that first experiment. But in any event, I conclude that an alcohol/PPG mix _will_ slowly evaporate the alchohol, although I suppose the importance of that when applying Rogaine does in fact remain to be seen.
Bryan
The main ingredients in Revivogen are the fatty acids, and those aren't going to "dry out" or "crystallize" on your scalp! It makes more sense to reverse the order: you put some spironolactone solution on your scalp, some of it dries out before it can be absorbed, then you apply some Revivogen later and it's the _Revivogen_ that comes to the rescue of the _spiro_ by dissolving the spironolactone again, giving it a second chance to be absorbed!
