Storing Radiesse Mixed With Lidocaine OK?

In addition to the potential issue already mentioned with sterility, the other practical reason that Radiesse cannot be stored is that after a few days, the product becomes hard and is then impossible to inject.  This is true whether it is mixed with lidocaine or not.  

    In general, radiesse should be injected once opened and not stored due to risk of contamination or infection.  Kenneth Hughes, MD Los Angeles, CA

Once you open up a filler syringe it is no longer sterile, so I wouldn't keep it to store if product is remaining per standard protocol fo the company (Merz).

It's better to use the full syringe of Radiesse and not store any unused portion.  Infection and contamination are theoretical risks with mixed stored products.  Radiesse comes in teo sizes: 0.8 mL and 1.5 mL, so if a lesser amount is needed, the smaller size can be used.

It is probably safe to store Radiesse with Lidocaine for a short amount of time but the problem is that no one knows how long this is because it is not an approved way to use Radiesse so there is no data. There are publications about other products and they show that the others were safe to store but there is nothing about safety or stability for Radiesse.
While the practice is probably fine, there is just no way to know and I typically inject full syringes and do not store anything.