Jenn, I'm so sorry to hear this. I was just reading my latest "Catnip" newsletter and there's a section where people can ask their cat questions to vets. One lady has 2 cats that have been spraying all over her house for several years. She took them to the vet and they're now on generic prozac and as long as she gives them a pill every 3 days, they don't spray. She's giving them 1/2 of a 10-milligram pill. She was also concerned if long term usage of this drug would be safe for her cats. The vet said that he hasn't seen any adverse effects with long term usage but he recommends that the cats receive annual check ups and blood work. He also said that sometimes a cats urine marking can be shut down by a few months course of Prozac but in other cases the medication is necessary long term. Maybe you can try something like this or another drug that is similar. Good luck.