Hi,
May I ask where you are? I usually get terramycin ointment from a supplier online, and haven't had a problem. Check out Valley Vet online.
If it's a copnjunctival issue in a cat, I believe tobramycin is an option but it depends on what the underlying cause of the conjunctivitis is. If it's chlamydia or mycoplasma, you should be fine with the antibiotics - but if not, only a vet obtain the antivirals.
Breeder
16 yrs experience with feline repro., nutrition, behavior