Mounjaro "5th" dose to vanish with new pen design

We've all heard of the 'golden dose' or the '5th dose' - that extra fluid leftover in the Mounjaro pen when someone has used all 4 weeks worth of doses.

But now it looks like that extra fluid in the pen is about the vanish thanks to a re-design of the KwikPen's mechanism...

The design of the Mounjaro KwikPen is about to change...

Eli Lilly have sent out official communication to pharmacies in the UK to state that the design of their infamous KwikPens is about to change.

Find the communication below:

"Eli Lilly & Company will be introducing a visual and structural update in the Mounjaro Kwikpen. The KwikPen device has been modified to reduce leftover medicine and make it easier to track that the final dose has been administered, indicating that the pen is ready to be discarded. The modified KwikPen works the same way as the initial device.

Current Mounjaro KwinPen vs new Mounjaro KwikPen

The initial and modified Mounjaro KwikPens are both disposable multi-dose single-patient-use pre-filled pens, containing the volume of solution necessary for priming before each injection and the delivery of 4 fixed 0.6mL doses (one dose administered weekly).

Mounjaro after the modification

We anticipate that the modified KwikPen will become available in the UK from April 2026. Once existing stock of the initial KwikPen is depleted, supply will transition to the modified KwikPen. Healthcare providers and patients can expect both versions to be available in the market for a period of time for all dose strengths during this transition.

The GTIN and PIP codes remain unchanged. Please continue to order as normal.

The modified KwikPen works the same way as the initial device, but there are a few visual and structural updates:

1. Plunger Position: The plunger sits farther down in the cartridge when the pen is unused.

2. Extended Plunger: A new internal component has been added behind the plunger, extending its length. This is shown in the Mounjaro KwikPen Guide to Parts section of the product’s Instructions For Use (IFU).

3. Remaining Medicine: After the fourth dose, the plunger will be near the end of the pen, clearly indicating the pen is ready to be discarded.

Please ensure that patients are advised about the KwikPen changes."

This is in response to the well-known practice of extracting the leftover priming fluid in the pen. Understandably, with costs as high as they are, people have been trying to maximise the usage of their Mounjaro pens.

Mounjaro after 4 doses have been administered, leaving priming fluid in the chamber (aka the '5th dose')

Unfortunately, this has led multiple bodies to accuse the general public of adopting unsafe practices and breaching the pen's intended usage to get that extra 'dose' out of the pen. This is a popular trend on social media, usually involving manual extraction of the leftover priming fluid with a needle and syringe.

If you have any questions or would like further information on the above, please let us know via email. We will continue to provide the current pens until they run out across the UK.

Thanks for reading!