The primary action we are concerned with is beta-2 receptor activity in adipose tissue in order to maintain enhanced lipolysis and in skeletal muscle in order to increase metabolic rate. There has been no research demonstrating up-regulation of adrenoceptors in these tissues with Ketotifen. The research everyone bases this theory on was looking at lung tissue of asthmatics if i recall.
I can't remember if if was Duchaine or Gundhil that came up with the original ketotifen hypothesis back in the late 90's, but there were lots of guys who attempted using it with clen and the anecdotal reports were very inconsistent, but basically noone was very impressed.
Ketotifen probably doesn't assist in lipolysis at all and histamine receptor antagonists actually seem to have some pretty profound negative metabolic potential. Lyle McDonald has recently discussed some of this research.
Even if there is some merit to the theory, bothering with this is pointless with proper EC use as there is no real evidence of meaningful down-regulation. EC studies of up to 6 months have demonstrated a continuous elevated metabolic rate - which far longer than it takes for severe down-regulation in response to potent selective agonists like clen.
Basically, if you have allergies that require anti-histamines in order to manage then take what you need, but these drugs are more likley to waste your money or even inhibit your progress from a body composition standpoint.
