cloratheshadow said:
Considering switching my Tirz out for Sema. So far Reta has been really good and I’m currently at 8.5 mg Tirz and 4mg Reta. I’m kind of wanting to focus on Reta and lowering Tirz. But it had me thinking…
If Sema has more GLP-1 than Tirz and Reta
And Reta has more GIP than Tirz
Wouldn’t it be more cost effective to just switch my Tirz for Reta? I’m already getting everything with Reta, so adding a small bit of Sema to it for added satiety sounds easier to me. Sema is so cheap, kits are like $50.
Is there any reason not to?
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Yes there is a reason not to. The info online about receptor affinities for the different GLP drugs is confusing and contradictory. Mainly as it depend a lot on who measured it and how and was it bound to albumin when it was tested ( in the body 99% of it is bound to albumin. ) Most of this info is in the preclinical papers under the drug development code names rather than under their sales names.
After reading a pile of papers on this, Tirzepatide has the strongest GIP agonism, not reta and I believe this is the main reason why tirz has the least side effects of all the GLP drugs, adjusted for weight loss effectiveness. The GIP agonism counteracts a lot of the GLP-1 adverse effects of nausea , vomiting , GI effects, malaise and food aversion. If reta really had stronger GIP agonism than tirz , it should cause less GI side effects and it does not.
Semaglutide is more potent at GLP-1 receptors than tirz or reta, but there are other factors. tirz and reta are used at higher doses , reducing this difference, and tirz is a biased agonist at GLP-1, allowing it to have larger downstream effects from the GLP-1 agonism, despite the lower affinity.
So I would expect swapping tirz for sema in that equation to substantially reduce GIP agonism, which would increase the side effects from reta, and I do not think the lower GIP agonism of reta would help a lot with the GLP -1 side effects from sema, as reta itself has stronger GLP-1 side effects than tirz.
So the main effect would be a bit more GLP-1 agonism , depending on the dose, though even this is not 100% clear given the biased agonism bit, and a lot less GIP , and the same glucagon. So more gastrointestinal side effects, and less weight loss effectiveness, given that tirz is better at causing weight loss than sema.
Depending on what you want to achieve by changing them around, more weight loss or less side effects?, what you are on will work better than sema/reta. Increasing the dose of either reta or tirz would likely reduce hunger and increase weight loss and makes the most sense and is simplest. Adding in low dose cagri or elora is another option if you still have a lot of weight left to lose, but I would increase reta or tirz first, unless side effects are the problem at current doses.