Issues Reported with Mounjaro KwikPen During Dosing

Tue 4th Feb, 2025

Patients have reported recurring issues with the Mounjaro KwikPen, particularly regarding its functionality during the third or fourth dose. Over 100 reports have been received about potential technical defects associated with this medication, which contains tirzepatide and is produced by Lilly.

According to Professor Dr. Martin Schulz, Chairman of the German Pharmacists' Medicines Commission (AMK), from May to September of the previous year alone, there were 149 reported cases of mechanical defects in the Mounjaro KwikPen. Each pen is designed to deliver four doses, which patients administer subcutaneously once a week.

Concerns have been raised in pharmacies about the pen becoming blocked during the latter doses, with reports indicating that the dosing wheel can also become unresponsive. Schulz noted that patients are returning to their local pharmacies with these issues, particularly struggling with the necessary venting process before injection. If the pen is vented excessively, it may lock prematurely, preventing the extraction of the medication.

The manufacturer has attributed these problems to user errors rather than a manufacturing defect. However, the Central Laboratory of German Pharmacists (ZL) did not find any production-related quality issues upon reviewing complaints and samples. The tested pens were able to deliver doses without significant remaining volume, which was attributed to overfilling.

Despite the findings, the AMK suspects that there are manufacturer-related factors that could lead to user errors, given the frequency of similar complaints from pharmacies. Consequently, the AMK has urged the pharmaceutical company to enhance the product to better meet patient needs. Key recommendations include:

  • Documentation Assistance: Patients should maintain a written record of their administered doses, as the information provided in the product's instructions is not prominently displayed. AMK suggests a separate document or clearer labeling on the packaging.
  • Scaling and Remaining Volume: The substantial remaining volume in the pen can confuse patients, leading them to believe they can administer additional doses. A clear numerical scale on the pen could help patients track their doses more accurately.
  • Use of Needles: The Mounjaro KwikPen does not include needles, which must be purchased separately. This requirement can lead to improper use of needles, including reuse, which may introduce air into the pen and necessitate excessive venting before use. The AMK recommends that the medication be packaged with the necessary needles to ensure patients have adequate supplies.
  • Temperature Guidance: The current product information only contains storage temperature guidelines and lacks instructions for warming the pen to room temperature before use. Cold storage can create a slight vacuum in the cartridge, making it easier for air to enter when a needle is attached.
  • Patient Education: Patients may require additional training on the proper use and storage of the pen, especially those using tirzepatide for weight management. The manufacturer should provide educational materials to aid in this process.

Schulz emphasized the importance of pharmacy teams in educating patients to ensure safe medication practices. The AMK is currently in discussions with the Federal Institute for Drugs and Medical Devices (BfArM) to initiate risk-reduction measures in collaboration with the manufacturer. Meanwhile, the AMK advises pharmacies to inform patients about proper handling and to report any additional concerns through their official channels.


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