I've used Benadryl in the past to keep receptors upregulated when using Clen. Here is a post from another board that compares Ketotifen to Benadryl:
I found this explanation on another board which appears to agree with a study I found on PubMed.
The study discusses the reduced degradation of methylated phospholipids which is associated with desensitization of the beta adrenergic receptors after prolonged stimulation. Sheez. Basically its preserving the membranes around beta receptors.
Anyways this is based around clen but should be the same general premise with albuterol or ephedra. So here u go:
"Due to the fact that clenbuterol is a beta-2 agonist/antagonist the downregulation of the cardiac, pulmonary and central nervous system beta-adrenergic receptors is an issue that users must combat when using this compound (3). A proven method to help alleviate this effect and ensure that the clenbuterol remains effective throughout its use is via the administration of ketotifen (7). Ketotifen is a prescription anti-histimines that acts to reduce beta-2 receptor activity. By reducing this activity, the receptor function is restored to nearly its original capability and the potency of the clenbuterol remains in effect. Doses of two to ten milligrams of ketotifen have been used by users of clenbuterol, but most would be well served to start at lower doses. It is unlikely that many will need doses higher then 5 milligrams per day. Taking ketotifen for seven days every two to three weeks should be enough to maintain well functioning beta-2 receptors and ensure that the clenbuterol maintains its effectiveness.
An alternative to ketotifen may be diphenhydramine, commonly referred to as Benedryl. Benadryl is a cationic ampiphylic drug, with this fact being significant because cationic ampiphylic drugs have the ability to inhibit phospholipase A2 and therefore upgrade beta-2 receptors (8). The inhibition of the enzyme phospholipase A2 is key due to it being responsible for methylated phospholipids. It is thought that by reducing and/or ending this action this allows the phospholipid membrane to remain relatively intact and the beta-adrenoreceptors will be able to remain functioning at their full capacity, or near to it, for much longer. For most, an effective dose would be 50-100mgs per day for seven days every three weeks while running clenbuterol. Users would be well served to take this dosage just prior to going to sleep as it will likely cause drowsiness.
Having said this, there is much more anecdotal feedback in regards to the effectiveness of ketotifen in relation to clenbuterol then there is Benedryl simply because ketotifen has been used much longer by strength athletes and bodybuilders for this purpose. As well, there is seemingly more direct research that indicates that ketotifen is effective while only a few studies suggest the same of Benedryl.. That is not to say that Benedryl is ineffective, just that there is less “real world” feedback as to its use with clenbuterol.
This prevention of the downregulation of the beta-2 receptors is important since it appears that clenbuterol gains effectiveness and produces its best results if it is run for six weeks or longer. This is true of fat loss and muscle mass gain it appears. For this reason most users will want to run clenbuterol for at least six weeks and ensure that they use some protection against receptor downregulation so that the clenbuterol remains effective throughout. "