What to do if your Mounjaro pen seems defective: warning signs, procedure to follow, patient rights, and pharmacist replacement.
Identifying a defective Mounjaro pen
The Mounjaro KwikPen is a reliable medical device, but like any manufactured product, occasional defects can occur. Signs of a potentially defective pen include: the injection button does not depress, no click is audible upon activation, the grey plunger does not fully descend after 10 seconds, significant liquid leakage, or the protective cap is damaged upon receipt.
It is important to distinguish a true defect from a handling error. The most frequent cause of “malfunction” is an incorrect injection technique: insufficient pressure on the button, premature withdrawal of the pen (before 10 seconds), or forgetting to remove the grey cap. Consult Eli Lilly’s instructional video or ask your pharmacist for a demonstration before concluding a device defect.
Visual inspections to perform
- Check the expiration date on the pen and the box
- Inspect the liquid: it should be clear, colorless to slightly yellow, without particles
- Verify that the cap is intact and that the mechanism slides normally
- Ensure that the pen has not been frozen (sound of internal crystals)
- Check that the lot number matches the one mentioned on the box
- Inspect the packaging for signs of damage during transport
Procedure in case of confirmed defect
If you notice a defect before injection, do not attempt to use the pen. Keep it in its original packaging and return it to your pharmacist. The pharmacist is authorized to exchange a defective pen for a new one and to report the incident to the ANSM via the pharmacovigilance system. This report is important for monitoring batch quality.
If the defect occurs during injection (the pen jams during administration), do not panic. The partially administered dose is generally safe. Do not attempt to complete the dose with a second pen. Note the incident and contact your doctor to determine the course of action: wait for the next injection or reschedule an early injection depending on the estimated quantity delivered.
Your rights as a patient
In France, patients have clear rights in case of defective medication. The pharmacist is obliged to exchange or refund a defective product. If the defect is confirmed, a pharmacovigilance report is mandatory (article R5121-161 of the Public Health Code). You can also directly report an adverse effect or quality defect on the ANSM reporting portal.
Eli Lilly has a patient relations service (toll-free number available on the leaflet) for quality complaints. The laboratory may request the return of the defective pen for analysis. Always keep the lot number and expiration date in case of a report. The MounjaGO app allows you to photograph and record pen information for reference.
Problem prevention
The majority of incidents are linked to improper storage or incorrect handling. Strictly adhere to storage conditions (2 to 8 degrees in the refrigerator, maximum 21 days out of the fridge at less than 30 degrees). Never freeze a pen. Take the pen out 30 minutes before injection to bring it to room temperature. Familiarize yourself with the mechanism before first use.
Upon receipt of your order at the pharmacy, immediately check the integrity of the packaging, the expiration date, and the cold chain (the pen should be cool to the touch). If the package was delivered by a carrier, ensure that the temperature was maintained during transport. Some online pharmacies include temperature indicators in their packages.
Track your progress with the MounjaGO app.
FAQ
How to know if my Mounjaro pen is defective?
A defective pen exhibits: a blocked button, absence of a click, a plunger that does not descend, significant liquid leakage, or cloudy/colored liquid. Before concluding a defect, check your injection technique with Eli Lilly’s video or your pharmacist.
What to do if my pen jams during injection?
Do not panic. Remove the pen, do not attempt to complete the dose with another pen. Note the incident and contact your doctor to determine the course of action. The partially administered dose is generally safe.
Can my pharmacist exchange a defective pen?
Yes, the pharmacist is obliged to exchange or refund a defective pen. Return the pen in its original packaging. The pharmacist will report the incident to the ANSM via the pharmacovigilance system.
How to avoid problems with the Mounjaro pen?
Respect storage conditions (2-8 degrees), never freeze, take the pen out 30 min before injection, and familiarize yourself with the mechanism. Check the packaging and expiration date upon receipt at the pharmacy.