Unopened Flea Medication: Cheristin For Cats 6 Month Supply; Purchased from Vet

I forgot that I had this on auto renew and have too much now. Purchased accidentally from vet office See photo of receipt - I purchased recently from vet. For a 6-month supply, it cost $120 with tax. Please see box for details, but it can be used with any cat (8 weeks or older and weighing more than 1.8 pounds)