My cat has been on 15 mg pheno twice a day for years with great success. Today when I went in to pick up his new Rx, I noticed it was now 16.2. The tech could only tell me they were the same dosages, but...if they're the same, then why do manufacturers make both 15 and 16.2 mg? It doesn't sound like a big difference to me, but I don't know enough about it. I don't want to overdose him! Any help/advice would be much appreciated. Thanks!