Hopefully samples should be arriving for most today or tomorrow. In the interest of harm reduction I'd like to reemphasize that this compound has an incredibly long half life.
SK_scientific and I dug a little bit more into the likely human half-life for dihexa. Here was our reasoning:
Due to metabolic and body composition differences, drugs administered to rats typically show a longer half-life when administered to humans.
The rat half life is 12.68 days[1]
SK_scientific was able to find an equation which allows you to estimate human kinetics based on rat kinetics. [2]
Here's some napkin math:
log10[half-life in human]=0.906*log10[half-life in rat]+0.723
[half-life in human]=antilog[0.906*log10[half-life in rat]+0.723]
[half-life in human]=antilog[0.906*log10[12.68*24]+0.723]
[half-life in human]=939.501 hours
[half-life in human]=39.1459 days
To put a 40 day half life into perspective. A common medication for hypothyroidism is levothyroxine. It has a rather long half life for a pharmaceutical - around 7 days. It takes 4-6 weeks to reach maximum serum concentration.
I couldn't find a documented method of determining maximum concentration from half life - though i can't imagine it's that hard. I finally just setup a basic spreadsheet and plotted it. I made the assumption that the dose is 20mgs once daily. On the y axis is mgs in circulation, on x is days.
Don't take this as anything more than a rough estimate. What I'm trying to point out is that circulating levels rise (nearly linearly) for a long time. Maximum concentrations won't be reached until around 200 days of constant use! Reaching this point may be neither safe nor desirable. Additionally, if you do experience negative effects, they could take a very long time to subside, unlike most traditional pharmaceuticals.
[1] - Evaluation of Metabolically Stabilized Angiotensin IV Analogs as Procognitive/Antidementia Agents - page 147
[2] - The Prediction of Human Pharmacokinetic Parameters from Preclinical and In Vitro Metabolism Data - see figure 6
I'm glad that DHXA addressed this as I was mulling over the best approach today while I was driving. Given that some amount of his samples will be readily available to people within a day or two, I contemplated the potential urgency of discussing this in forum. Thanks for putting that together for everybody, DHXA.
I should let everyone know that I have contacted a Toxicologist to get some thoughts on the equation that we located, and any potential other variables involved in determining half life when converting data from rodent to human. Unfortunately that individual will be out of the office for several more days.
It MAY turn out that one would only need to dose with this substance once every couple of weeks or once per month to reap benefits. And as DHXA pointed out, we should absolutely be certain to stress that "Mega Dosing" be avoided at all costs. This is not a psychoactive compound like most of the drugs that people are used to taking. You're obviously stuck with your decision for a good while once this is in your plasma. Daily use in and of itself could prove wasteful even if it were found out that the drug was safe in high circulating concentrations.
Anyhow, once I speak with the Toxicologist, we'll share what we know. Until then, take all of this into serious consideration for your own safety.
Edited by sk_scientific, 18 July 2014 - 07:39 PM.