Is there a support medicine for early kidney failure in cats

Hello, my name is***** and I have over 20 years of experience as a veterinarian. I understand that you are concerned about keeping Elsa as healthy as possible now that she has been diagnosed with early kidney failure.
If her urine is cultured and she has any signs of infection then she absolutely she should be placed on antibiotics as a first measure. Infections can cause kidneys to fail, or worsen failure.
If she has no signs of an infection there are other things we can do to help her kidneys function better longer. What is done depends upon what stage she is in.
It may help you to look at this website which explains how kidney failure is staged in cats and dogs. The higher the stage the more severe failure is present and the more medications that may be needed to keep her healthy: http://www.iris-kidney.com/pdf/IRIS2009_Staging_CKD.pdf
Diets low in quantity, but consisting of very high quality, protein such as Hills k/d or Royal Canin low protein renal diet, can help as then the kidneys don't have to work as hard are an important part of therapy. But most important is that she eats, so if she refuses to eat prescription foods a high quality senior food is another option.
I also recommend an omega 3 fatty acid to reduce inflammation and hypercoaguability. Good brand name omega 3's to try are 3V Caps or Derm Caps. I recommend a dose based upon the EPA portion (eicosapentanoic acid) of the supplement as if we do that the rest of the supplement will be properly balanced. Give her 10mg to 20mg of EPA per pound of body weight per day. For example an 8 pound cat could take 80mg to 160mg of EPA per day.
Supplements such as Azodyl to change gut bacteria to help decrease urea in the gut which would be absorbed into the blood, and epakitin to decrease phosphorus levels are other possible options.
Long term therapy for this disease is subcutaneous fluid therapy at home if needed to keep the enzyme levels down.
Other possible medications that may help are those to control hypertension and protein loss in her urine if protein is present in high levels in her urine, phosphate binders if high blood phosphorus levels are present, and potassium supplements if her potassium levels are low.
Best of luck with Elsa, please let me know if you have any further questions.