Penicillin (Fish Pen) is labeled for fish. 30 count. This is a general "all purpose" antibiotic. It is effective against susceptible gram-positive bacteria and anaerobes. The oral dosage for Penicillin is 5 mg per pound of dog given every 8 to 12 hours, depending on the severity of the problem. The fish-version of penicillin (Fish-Pen) is in 250 mg tablets. Use with caution if your're animal is allergic to penicillin. You would need 1 tablet per dose for a 50 pound dog.
Always contact your veterinary for information or an appointment for your pet. We would never recommend skipping an appointment or proper care. If you have any question please consult your vet for proper doses and risk factors.