Dogs with bacterial infections need veterinary-prescribed antibiotics, and the specific drug depends on where the infection is and what bacteria are causing it. There is no safe over-the-counter antibiotic you can give your dog at home without a prescription. The good news is that most bacterial infections in dogs respond well to a handful of commonly used antibiotics, and treatment courses are relatively straightforward once your vet identifies the problem.
The Most Commonly Prescribed Antibiotics
Data from a veterinary teaching hospital shows that five antibiotics account for the vast majority of prescriptions for dogs with confirmed or suspected infections. Amoxicillin-clavulanate tops the list at about 25% of all therapeutic antibiotic prescriptions, followed by cephalexin (18%), enrofloxacin (17%), plain amoxicillin or ampicillin (15%), and doxycycline (11%). Each one targets different types of bacteria and works best for specific kinds of infections.
Your vet will choose based on the infection’s location, severity, and sometimes the results of a bacterial culture. A culture identifies exactly which bacteria are involved and which drugs will kill them. For straightforward infections, vets often start with a broad-spectrum antibiotic and adjust if the dog doesn’t improve within a few days.
Skin and Wound Infections
Skin infections (called pyoderma) are one of the most common reasons dogs end up on antibiotics. These range from superficial infections that cause flaky, crusty patches and hair loss to deep infections involving painful, oozing sores. Amoxicillin-clavulanate and cephalexin are the go-to choices for most skin infections.
Amoxicillin-clavulanate is FDA-approved for treating wounds, abscesses, and skin infections in dogs. For surface-level infections, treatment typically runs 5 to 7 days, or 48 hours past the point when symptoms disappear. If there’s no improvement after five days, your vet will likely switch to a different approach. Deep skin infections are a different story: they can take 4 to 6 weeks of antibiotics to fully clear, with a maximum treatment window of 30 days for amoxicillin-clavulanate specifically.
Cephalexin is another workhorse for skin infections. Studies show that both once-daily and twice-daily dosing schedules are equally effective, with most superficial infections resolving in 14 to 42 days (median of about 28 days). The key rule for skin infections is to keep giving the antibiotic until the infection looks and feels completely healed, then continue for an additional 7 days for superficial infections or 14 days for deep ones. Stopping too early is one of the most common reasons skin infections come back.
Urinary Tract Infections
For a simple, uncomplicated UTI, guidelines from the International Society for Companion Animal Infectious Diseases recommend amoxicillin or trimethoprim-sulfonamide as first-line treatments. A standard course lasts about 7 days, though vets have traditionally prescribed 7 to 14 days. Shorter courses appear to work for straightforward cases.
Complicated UTIs, which include recurring infections or those in dogs with underlying health conditions like diabetes or kidney disease, typically require about 4 weeks of treatment. If the infection has spread to the kidneys (pyelonephritis), expect 4 to 6 weeks of antibiotics. Your vet will likely want a follow-up urine sample after treatment ends to confirm the infection is truly gone.
Dental and Oral Infections
Clindamycin is the antibiotic most associated with dental infections in dogs. It works by shutting down bacterial protein production, effectively stopping bacteria from growing and reproducing. It’s particularly useful for oral infections because it’s effective against both the oxygen-loving and oxygen-avoiding bacteria commonly found in the mouth. Clindamycin is given orally every 12 hours, making it a relatively simple twice-daily medication to administer.
Tick-Borne Infections
Doxycycline is the primary antibiotic for tick-borne bacterial diseases in dogs, including ehrlichiosis and Lyme disease. It accounted for about 11% of all antibiotic prescriptions in veterinary hospital data, and the overwhelming majority of those prescriptions were specifically for confirmed or suspected tick-borne infections. If your dog tests positive for a tick-borne illness, doxycycline is almost certainly what your vet will reach for.
Antibiotics to Be Cautious About in Puppies
Enrofloxacin, a fluoroquinolone antibiotic, is effective against many bacterial infections but comes with serious risks for young, growing dogs. It causes damage to developing joint cartilage, including thinning of the cartilage, loss of cartilage cells, and structural gaps in the cartilage matrix. This has been confirmed across multiple animal species. Enrofloxacin should not be used in growing puppies, and vets exercise extra caution with it during the reproductive period as well. In adult dogs, potential side effects include digestive, immune, and nervous system problems.
Supporting Your Dog During Treatment
Antibiotics kill harmful bacteria, but they also disrupt the beneficial bacteria in your dog’s gut. This is why diarrhea and digestive upset are common side effects of almost any antibiotic course. Probiotics can help maintain gut health during and after treatment.
Cornell University’s veterinary college specifically recommends probiotic products like Fortiflora and Proviable, both of which have clinical studies supporting their use in dogs. Beneficial probiotic strains for dogs include Enterococcus faecium (strain SF68), Bifidobacterium animalis (which helps with acute diarrhea), and Lactobacillus acidophilus (which improves stool quality). You can also support gut health with prebiotic fiber, which feeds the good bacteria already living in your dog’s intestines. Starting a probiotic at the beginning of the antibiotic course, rather than waiting for digestive problems to appear, is the better strategy.
Why the Right Antibiotic Matters
Giving the wrong antibiotic, using the wrong dose, or stopping treatment too early doesn’t just fail to fix the infection. It actively contributes to antibiotic resistance, where bacteria evolve to survive drugs that used to kill them. The FDA released a five-year plan in 2023 specifically aimed at improving antibiotic stewardship in veterinary medicine, reflecting how seriously this problem is taken.
This is also why you should never give your dog leftover antibiotics from a previous illness, share antibiotics between pets, or use human antibiotics without veterinary guidance. The dosages, drug choices, and treatment lengths are specific to the type of infection, the bacteria involved, and your individual dog’s size and health status. What worked for one infection may be completely wrong for the next one, even in the same dog.