Why is the weight loss peptide Semaglutide dose not administered according to body weight?

Why would a 150-pound person lose weight using the same dose of Semaglutide (Tirzepatide or Retatrutide) as a 350-pound person? Why not set the dosage according to body weight?

By searching the relevant data, we summarized the reasons why weight loss peptides (such as Semaglutide, Tirzepatide and Retatrutide) are not usually administered according to body weight as follows.

The mechanism of action of drugs

Weight loss drugs such as Semaglutide Tirzepatide and Retatrutide regulate appetite and metabolism by mimicking the effects of hormones such as incretin (GLP-1). GLP-1 and other receptors mainly exist in the digestive system, pancreas and nervous tissues of the human body, and there are not many GLP-1 receptors in the body’s fat and muscle. Therefore, the effect of using a GLP-1 receptor agonist is actually related to the concentration of the drug and the interaction with the receptor, rather than body weight.

So, this is one of the reasons that GLP-1 agonists are with fixed dose instead of increasing dose with weight gain.

Individual difference

In Semaglutide’s corresponding trial, people with a larger weight base actually lost weight faster. Therefore, weight is a factor that affects the effect of drugs, but this factor is not particularly obvious. Many other factors can affect the actual effectiveness of Semaglutide, such as individual differences.

Individual pharmacokinetics (absorption, distribution, metabolism, and excretion of drugs in the body) and pharmacodynamics (intensity and duration of drug effects) may vary depending on other factors, such as age, sex, liver and kidney function, etc. Therefore, the use of a fixed dose can reduce the complexity of dose adjustment due to individual differences.

So this is another reason that GLP-1 agonists such as Semaglutide with fixed dose instead of increasing dose in response to weight gain.

Dose-dependent side effects

As the dose increases, the side effects of the drug may become more significant. Therefore, adopting a fixed dose can help to reduce the risk of side effects while providing therapeutic benefits.

Clinical trial data support

The dosage of these drugs is usually based on a large amount of clinical trial data. In these trials, the researchers identified a standard dose that would be effective and safe in most cases. These dosages were set with subjects of different weight groups in mind, and clinical trials have demonstrated that fixed dosages produce effective results in individuals of different weights.

Drug safety and operability

The fixed dose is more convenient for clinical operation and reduces the complexity of dose calculation and the potential risk of medication error.

In summary, although body weight is one of the important factors affecting drug metabolism and action, other factors are more important when using slimming peptides Semaglutide Tirzepatide and Retatrutide, so it is more reasonable and safe to use a fixed dose of administration.