It requires a prescription and tastes awful. It is used in dogs who require AB on a long term basis (eg for dogs with IBD/autoimmune diseases or staph/sepsis). Tylan is also the drug most often used in chickens and other slaughter meat - when you hear about farmers giving their animals AB this is the one they use. It is not something you should give ad hoc. There has been increasing levels of AB resistance developing due to it's wide spread use, which is why access was restricted and it's approval for use in livestock is being phased out in many countries. Because of this issue with resistance, and it's important role in treating some very serious diseases in dogs, it is not used as a first line prescription. Flagyl (metronidazole), amoxicillan or a sulfonamide will always be prescribed first. You don't want your dog developing a resistance to it in case they get very sick. I really encourage you not to use Tylosin (or any antibiotic) unnecessarily.