I have never had a problem with it dissolving.  I don't know if yours comes the same way ours does or not.  We get a premeasured syringe that contains the powder and a sterile liquid with the stopper in between.  We push up the plunger to a designated mark which forces the liquid into the chamber containing the powder.  I always shake for a few minutes and it is fully dissolved.  I do note that you must tap or shake the syringe first to be sure none of the powder is "stuck" to the sides.  If  it is, I gently tap the side of the syringe to dislodge it.  The only problem I have ever had is a defective pack that came during  the summer.  Somehow the package was sealed, but when I opened it the tab on the syringe that you have to first remove was missing and the liquid and powder were already mixed.  Since this is a medication that must be used after mixing and cannot sit around indefinitely, I contacted my prescription pharmaceutical company (we do mail order) and they sent me a new pack. Do you buy yours locally at a pharmacy or through mail order?  If  it is mail order, please be sure they ship it in a styrofoam cooler with a cold pack to keep it cool until you get it. It is ok at room temp, but I understand extreme  heat is not good for it and may affect it.  They always ship mine to my office and call me first to be sure I will be here to receive it.