Ketotifen was made popular by its ability to inhibit the down regulation of beta receptors caused by drugs like clenbuterol. Clenbuterol, albuterol, and Ephedrine used to be cycled on and off because they desensitize the various receptors they act on to produce their lipolytic effect. Ketotifen would therefore allow the use of these fat burning drugs for much longer periods.

IBenadryl (the anti-histimine) can also be used for this same purpose, and is 10x cheaper and infinitely more available to most people.

Ketotifen, in medical circles, is also recognized for its ability to lower levels of the cytokine Tumor Necrosis Factor-alpha (TNF-alpha), which is a catabolic hormone, and this is a property that Benadryl does not have to my knowledge. TNF-alpha lowers both testosterone and IGF-1 levels, and strenuous exercise elevates TNF-alpha levels (5). TNF-alpha has also been shown to increase insulin resistance.

Ketotifen and Weight Loss

Ketotifen is used by people suffering from wasting diseases partially caused by TNF-alpha. I think, however, its ability to lower TNF-alpha is going to be overshadowed by anabolic effects produced by anabolic steroids. In one study involving AIDS patients, combining Ketotifen and Oxymetholone (Anadrol 50) showed that the Ketotifen didn´t add much to the Oxymetholone induced weight gain. Benadryl is simply too much cheaper and readily available to use Ketotifen in its place with Clen. However, for Post-Cycle-Therapy, Ketotifen and it´s ability to lower TNF-alpha, is a very valuable tool. Hypogonadism (low testosterone) often accompanies elevated TNF-alpha levels (6), and after a cycle of anabolic steroids, you are going to be in a hypogonadal state, with elevated TNF-alpha. Thus, taking Ketotifen with your PCT is probably a very good idea. 1-3mgs/day is recommended before bed because this stuff will make you drowsy.

Source: steroid.com