Because misuse is dangerous and can lead to antibiotic resistance, penicillin medications are available only by prescription. Discovered in 1928, penicillin is one of the first antibiotic medications developed, and its various formulations remain useful for eradicating a variety of pathogenic bacteria. If your dog needs it, your veterinarian will provide the proper formulation and dosage depending on your dog's condition and the nature of the infection.
Prohibited Without Prescription
Penicillin disrupts the cell-wall-building capabilities of sensitive bacteria, ultimately killing them and wiping out the infection. This makes it helpful for treating a wide variety of both aerobic and anaerobic bacteria. However, as with most antibiotics, improperly using penicillins allows bacteria to develop resistance that ultimately renders such medications worthless and significantly complicates treatment. Because of this serious risk, along with the potential for allergic reactions and the role penicillin plays in human medicine, you must obtain a prescription to purchase the drug.
Treating bacterial infections is not as simple as noting your dog has a stomach bug or an infected cut, then prescribing a few pills. Usually, your veterinarian will take a thorough history, perform a physical exam, take samples and have them cultured to determine the causal organism and its sensitivity to different medications before prescribing one. After accurately weighing your dog, your vet will calculate the correct dosage, taking into account the myriad variables involved. Because most lack the resources and capabilities to provide this level of care, pet owners should avoid using penicillin prescribed for other people or pets to treat their dogs.
Follow the instructions and heed the warnings printed on the medication. Note, for example, that you should offer some penicillin medications with food, while others require an empty stomach for maximum efficacy. Some types of penicillin are best absorbed when administered one hour before or two hours after eating, according to Pet MD. If you have trouble administering the medication properly or have questions about the correct dosage, contact your vet and get clarification. Unless instructed otherwise by your vet, complete the entire course of antibiotics -- even after your pet's condition improves.
Even with strict adherence to the medication guidelines, side effects may occur with penicillin. Most side effects, such as gastrointestinal upset, loss of appetite or the development of a skin rash, are relatively mild, but prolonged use may cause serious side effects, such as breathing difficulties, swollen limbs or uncoordinated behavior. Be especially observant for signs of an allergic reaction, which can be fatal. Seizures, shock, facial swelling, sudden vomiting and diarrhea are some of the symptoms of allergic reactions. Contact your veterinarian immediately if you suspect your pup is suffering from such a reaction.