Why does everyone get the same first dose lease?

[Overhaul54]

Can anyone explain why the jabs don't take weight into account for efficacy?
I'm struggling to work out how 2.5mls works on both 12 stone and 22 stone people.

Because it's acting on the pancreas and the brain, not the whole of your body.

Because the dose isn't based on weight? Very few medications are.

Well I thought because the 2.5 is therapeutic, to get you used to it, the amount was relevant.

My friend is morbidly obese. She can drink like a fish and not feel the effect and needed an extra dose of anesthetic because she was still awake on the suggested dose.

I get brains are the same size but doesn't the amount of insulin you need depend on how much blood sugar there is. Wouldn't more of you mean there was a difference to someone with less weight?

See first answer. It's not based on weight

Alcohol, anaesthetics and insulin are different drugs with different actions and different effects. Tirzepatide has been shown via the research to be weight independent.

I was morbidly obese, exactly 22 stones coincidently, when I first started taking Mounjaro. It had an effect from day one with very strong suppression. I've been taking it for 35 weeks and have not gone beyond the 7.5mg dose. So clearly weight does not affect the action of the medication.

Once the medication is in your blood stream it can act on your brain and pancreas.

Yeah and my starting BMI was 32 at 5'2 so at the smaller end of WLI users but didn't realise feel much until 10mg so obviously not based on weight.

"Well I thought because the 2.5 is therapeutic, to get you used to it, the amount was relevant."

The 2.5mg is not a therapeutic dose, which means it isn't intended to produce weight loss for the majority of people. In the clinical trials the first dose that produced statistically significant weight loss was the 5mg dose. The 2.5mg dose was used for 4 weeks as a step to the 5mg dose. The other doses studied were the 10mg and the 15mg dose with the 7.5mg and 12.5mg doses being used for 4 weeks S stepping up doses.

It is not a fat soluble (the irony! 🤣) medication so dose is the same for any weight.

Calculating maximum doses for drugs* is based on weight, but it "maxes out" at 70kgs. It's because larger patients still have the same sized liver, kidney etc, and still metabolise the drug at the same rate.

*disclaimer: my experience is mostly in local anaesthetics.