Introduction to Mounjaro

Mounjaro (tirzepatide) has taken the weight loss and diabetes management world by storm. Originally developed by Eli Lilly as a dual GIP and GLP-1 receptor agonist, Mounjaro was first approved in May 2022 by the FDA for the treatment of Type 2 diabetes. Its mechanism of action, targeting two different incretin receptors, has led to unparalleled weight loss results in clinical trials, making it a competitor to other GLP-1-based weight loss drugs like Ozempic (semaglutide) and Wegovy.

Since its approval, many patients and healthcare providers have turned to Mounjaro not just for diabetes control but for significant weight loss. Clinical trials have shown that patients on the highest dose of tirzepatide lost up to 22.5% of their body weight—a result that has made the drug widely sought after.

However, a growing number of users have begun questioning an unusual observation—why does each prefilled pen contain more medication than what is actually dispensed? This blog will explore why there is an “extra dose” inside the syringe, whether it is legally required, and why patients cannot access it.

The Science Behind Mounjaro’s Success

Mounjaro is a dual agonist that works on two incretin hormones:

  1. GLP-1 (Glucagon-like Peptide-1) – This receptor slows digestion, regulates blood sugar, and promotes a feeling of fullness, helping reduce calorie intake.
  2. GIP (Glucose-dependent Insulinotropic Polypeptide) – Enhances insulin release and fat metabolism, potentially increasing fat burning.

This dual action makes Mounjaro unique compared to drugs like Ozempic and Wegovy, which act only on the GLP-1 receptor.

How It Became Popular for Weight Loss:

  • Initially approved for Type 2 diabetes, studies quickly revealed that tirzepatide resulted in unprecedented weight loss.
  • Demand surged, leading to shortages as many doctors prescribed it off-label for obesity.
  • In late 2023, Eli Lilly received FDA approval for Zepbound, a tirzepatide formulation specifically marketed for weight loss.

This rise in popularity has also led to more scrutiny, particularly regarding its delivery system and the so-called extra dose inside the injector pen.

The Extra Dose: Why Is It There?

Many Mounjaro users have noticed that their prefilled injector pens contain more liquid than what is actually dispensed. This has led to speculation and frustration as patients wonder why this extra medication cannot be accessed or used.

Reasons Behind the Extra Dose:

  1. Regulatory and Safety Requirements
    • Drug manufacturers must overfill syringes to ensure that the correct full dose is delivered.
    • Some of the drug is lost within the needle, pen mechanism, or tubing.
    • Regulatory bodies like the FDA and EMA require this extra volume to guarantee that the exact prescribed dose reaches the patient.
  2. Pharmaceutical Manufacturing Standards
    • Syringes, cartridges, and pens are mass-produced and standardized.
    • If a pen exactly matched the required dose, slight variations in production could lead to under-dosing, which is unacceptable for regulatory approval.
    • The slight overfill ensures consistency and compliance with medical standards.
  3. Prevention of Contamination and Waste
    • Prefilled syringes are single-use only.
    • The drug inside is not preservative-free, meaning that any attempt to reuse or extract excess medication could introduce bacteria and lead to infections.
  4. Legal and Patent Protections
    • Eli Lilly has a strict patent on the delivery mechanism and dose regulation.
    • The design ensures patients cannot accidentally or intentionally extract more than the approved dose.
    • Allowing access to extra medication could violate controlled dosing regulations and increase the risk of side effects.
  5. Clinical Efficacy and Safety
    • Tirzepatide is dosed based on weight-based clinical trials.
    • Any excess medication taken beyond the approved dose could lead to unintended side effects, including severe nausea, vomiting, or pancreatitis.
    • Patients should never attempt to extract or inject more than what the pen is designed to deliver.

Patient Frustrations and Ethical Concerns

While the pharmaceutical rationale is clear, many patients feel that this overfill is wasteful, especially given the cost of the Drug 

Some have even tried to extract the leftover liquid from the pen, but this is highly discouraged due to:

  • Risk of contamination
  • Potential for incorrect dosing
  • Legal and safety concerns
  • Lack of sterility once the pen has been used

Despite patient concerns, Eli Lilly maintains that the design is essential for ensuring dose accuracy and preventing misuse.

How Mounjaro Compares to Other Weight Loss Injections

1. Wegovy & Ozempic (Semaglutide)

  • Single GLP-1 receptor agonist
  • Weekly injections, starting at 0.25mg and titrating up to 2.4mg
  • Patients report similar issues with overfill in pens

2. Saxenda (Liraglutide)

  • Daily injections
  • Higher flexibility in dosing, meaning less waste
  • Still follows similar syringe overfill standards

Compared to Mounjaro, all these drugs contain a similar safety overfill mechanism, which is a common pharmaceutical standard.

Will There Ever Be a Way to Use the Extra Dose?

It is highly unlikely that regulatory agencies will change the design of Mounjaro pens to allow access to the unused liquid. Here’s why:

  1. Strict Dosing Guidelines: Any deviation from prescribed dosages would violate FDA, EMA, and MHRA guidelines.
  2. Liability Issues: If patients self-adjusted doses, it could lead to complications and potential lawsuits.
  3. Injection Sterility: Prefilled syringes are not designed for multiple uses.

The only potential change in the future would be if Eli Lilly decides to release multi-dose vials—but given their financial and safety motivations, this is unlikely.

Conclusion: Understanding the Extra Dose in Mounjaro

Mounjaro has revolutionized weight loss and diabetes treatment, but its delivery system follows pharmaceutical industry standards to ensure safety and precision. While patients may feel frustrated by the extra liquid in their syringes, the reasons behind it are well-founded in regulatory, legal, and safety requirements.

Unfortunately, there is no legal or safe way to access the extra medication, and patients should never attempt to extract additional doses beyond what the pen is designed to deliver.

If you’re considering Mounjaro for weight loss, always consult with a healthcare professional to ensure that you are receiving the correct dose and understand how the medication works for your specific health needs.Its so important and its a great Drug.