Zymox and Posatex are different. Posatex is an antifungal, anti-inflammatory, and antibacterial drug and helps get rid of Otitis Externa in dogs only. Zymox is for both cats and dogs and helps recover from a chronic and acute infection in the ear due to yeast, fungal or bacterial infection. Zymox has hydrocortisone which brings down itching issues. Both Posatax and Zymox need to get administered once a day.