minoxidil Question
- Thread starter Jack23-
- Start date
casperz
Experienced Member
- Reaction score
- 25
Since no one else has responded, I'll GUESS that your safe waiting 4 hours.
I would think if it has not been absorbed by that time it's not going to. But
that is just a guess.
What brand minoxidil are you using? I use Kirklands and I don't think it
affects my hair that much. But I do remember about 10 years ago
using Rogaine and it did make my hair greasy.
I would think if it has not been absorbed by that time it's not going to. But
that is just a guess.
What brand minoxidil are you using? I use Kirklands and I don't think it
affects my hair that much. But I do remember about 10 years ago
using Rogaine and it did make my hair greasy.
- Reaction score
- 42
Actually, 4 hours has long been considered the standard amount of time to wait for (reasonably) full absorption, so the original poster is good to go! 
This is based on an old study which measured the amount of systemic absorption of topical minoxidil after various lengths of time of having it sit on test subjects' scalps, and it was close enough to being complete absorption after 4 hours. Interestingly, the absorption happened the quickest during the first hour or so, then slowed down considerably. If I remember correctly (I need to go back and re-read the study again to be sure), something like 75% absorption happend during THE FIRST HOUR, then slowed way down after that. But 4 hours is definitely good enough!
This is based on an old study which measured the amount of systemic absorption of topical minoxidil after various lengths of time of having it sit on test subjects' scalps, and it was close enough to being complete absorption after 4 hours. Interestingly, the absorption happened the quickest during the first hour or so, then slowed down considerably. If I remember correctly (I need to go back and re-read the study again to be sure), something like 75% absorption happend during THE FIRST HOUR, then slowed way down after that. But 4 hours is definitely good enough!
- Reaction score
- 42
Damnit, I just suddenly realized that the study I just referred to in my previous post is the same one I've been beating "LostAnagenCycle" over the head with in that other thread!
The abstract is below (note that I misremembered the numbers a little bit...the important part of the abstract I put in bold):
J Pharm Sci. 1990 Jun;79(6):483-6.
"Relationship between contact time of applied dose and percutaneous absorption of minoxidil from a topical solution." Ferry JJ, Shepard JH, Szpunar GJ.
Clinical Pharmacokinetics Unit, Upjohn Company, Kalamazoo, MI 49001.
Twenty-two healthy male volunteers completed a four-way, multiple-dose, randomized crossover study to determine the relationship between contact time of applied drug on the scalp and minoxidil absorption from a 2% topical solution. One milliliter of solution was applied twice daily over 150 cm2 of bald scalp to each subject for 6 days. Unabsorbed drug was washed off the scalp after 1, 2, 4, and 11.5 h of contact time in each of four treatments. Cumulative urinary excretion profiles within steady-state, 12-h dosing intervals were well described by straight lines for all treatments, indicating that systemic minoxidil elimination was rate controlled by constant, zero-order percutaneous drug absorption. The extent of minoxidil absorption, expressed as steady-state urinary excretion of unchanged minoxidil, minoxidil glucuronide, or the sum of these, increased in a disproportionate manner with increase in contact time of drug on the scalp. Relative to the amount absorbed after a contact time of 11.5 h, absorption was approximately 50% complete by 1 h and greater than 75% complete by 4 h. This suggests that minoxidil absorption from the vehicle into skin occurs rapidly relative to diffusion through skin. The rate of minoxidil absorption from vehicle into skin was characterized as nonlinear, whereas minoxidil excretion into urine was rate controlled by diffusion from one or more components of the skin which apparently serve as a reservoir, or depot, for minoxidil.
The abstract is below (note that I misremembered the numbers a little bit...the important part of the abstract I put in bold):
J Pharm Sci. 1990 Jun;79(6):483-6.
"Relationship between contact time of applied dose and percutaneous absorption of minoxidil from a topical solution." Ferry JJ, Shepard JH, Szpunar GJ.
Clinical Pharmacokinetics Unit, Upjohn Company, Kalamazoo, MI 49001.
Twenty-two healthy male volunteers completed a four-way, multiple-dose, randomized crossover study to determine the relationship between contact time of applied drug on the scalp and minoxidil absorption from a 2% topical solution. One milliliter of solution was applied twice daily over 150 cm2 of bald scalp to each subject for 6 days. Unabsorbed drug was washed off the scalp after 1, 2, 4, and 11.5 h of contact time in each of four treatments. Cumulative urinary excretion profiles within steady-state, 12-h dosing intervals were well described by straight lines for all treatments, indicating that systemic minoxidil elimination was rate controlled by constant, zero-order percutaneous drug absorption. The extent of minoxidil absorption, expressed as steady-state urinary excretion of unchanged minoxidil, minoxidil glucuronide, or the sum of these, increased in a disproportionate manner with increase in contact time of drug on the scalp. Relative to the amount absorbed after a contact time of 11.5 h, absorption was approximately 50% complete by 1 h and greater than 75% complete by 4 h. This suggests that minoxidil absorption from the vehicle into skin occurs rapidly relative to diffusion through skin. The rate of minoxidil absorption from vehicle into skin was characterized as nonlinear, whereas minoxidil excretion into urine was rate controlled by diffusion from one or more components of the skin which apparently serve as a reservoir, or depot, for minoxidil.
Wow, thanks so much Bryan and Casperz!! (and i use Kirkland too btw Casperz)
It's good to hear these statistics as i've been quite worried about this. Most days now i wash out the minoxidil,on average of about 3/4 hours after application, so it's good to know i'm getting more or less the full absoption.
I think this is an issue that needs to be stressed more overtly in the literature of the products.
:dunno:
It's good to hear these statistics as i've been quite worried about this. Most days now i wash out the minoxidil,on average of about 3/4 hours after application, so it's good to know i'm getting more or less the full absoption.
I think this is an issue that needs to be stressed more overtly in the literature of the products.
:dunno:
- Reaction score
- 42
Jack23- said:
I totally agree with that. If anything, I think the literature should err on the side of giving TOO MUCH information. To hell with this idea of giving too little information, and then make the users have to guess about what to do! :nono:
- Reaction score
- 42
casperz said:
Even if you applied Rogaine at bedtime and then went to sleep for 8 or 9 hours and then jumped in the shower and shampooed the next morning, you'd STILL be losing a little. I guess for optimum efficiency, you'd have to apply your two daily doses at exactly 12-hour intervals!
Bryan,
Doesn't the rate of absorption depend on the vehicle? I was under the impression that higher the alcohol content(80%-90%) minoxidil absorbs fast. I vaguely remember Dr. Lee using quoting this as an excuse and recommending to his patients that to get most of the benefits from xandrox 15 or his higher alcohol solutions to wash the hairs after an hour or two.
If you are not sure, can provide a guess on absorption rate and vehicle type?
Doesn't the rate of absorption depend on the vehicle? I was under the impression that higher the alcohol content(80%-90%) minoxidil absorbs fast. I vaguely remember Dr. Lee using quoting this as an excuse and recommending to his patients that to get most of the benefits from xandrox 15 or his higher alcohol solutions to wash the hairs after an hour or two.
If you are not sure, can provide a guess on absorption rate and vehicle type?