Long story short, I have been in a 2.5 month cluster with a 1 week break that I attribute to Benadryl - thanks to Batch and everyone here who has shared their wisdom. I am currently on my 2nd Medrol pack in 3 weeks trying to kill this sucker. I have also fully started up the d3 regimen about 4 days ago - minus the K2 which I am waiting to be delivered.
Since my earlier success with Benadryl I have been taking it quite a bit but noticing that it's not having nearly the same effect this time around. From what I've read, you can build a tolerance to it. I'm wondering if Doxylamine Succinate would have a similar effect since they are both 1st generation antihistamines?

Genever,

Good question.  Doxylamine has roughly the same Tmax, (time to effective/therapeutic serum concentration after oral dose) with a few hours longer to half-life than Diphenhydramine so it should work just fine. 

Regarding Diphenhydramine not having the same effect as previous...   The best answer is we're dealing with a numbers problem kind of like playing a game of whack-a-mole except with millions if not billions of moles... 

What we're dealing with are the relative serum concentrations of histamine and the H1 histamine blocker (Doxylamine or Diphenhydramine) trying to occupy the same H1 histamine receptor on genes within neurons throughout the body and in particular the trigeminal ganglia.  If the serum concentration of histamine is greater than that of Diphenhydramine due to a longer dosing interval for Diphenhydramine, the higher the probability of histamine reaching and occupying the H1 histamine receptor...  When this happens, Diphenhydramine will be less effective and the CH beast jumps ugly.

Accordingly, a 4 hour dosing interval with Benadryl (Diphenhydramine HCL) with either a 25 mg tablet or 12.5 mg dose of the liquid form should result in its serum concentration being higher than that of histamine.  That should translate to a higher H1 histamine receptor occupancy by the Diphenhydramine molecule resulting in more CH pain free time.  Hope this helps.

Take care,

V/R, Batch

Very helpful. Thank you!