Cats can safely take several classes of antibiotics, but only when prescribed by a veterinarian who has evaluated the specific infection. The most commonly used options include amoxicillin-clavulanate, cephalexin, clindamycin, doxycycline, and metronidazole. Each one targets different types of bacteria and carries its own risks, so the right choice depends on where the infection is and what’s causing it.
Giving your cat a human antibiotic from your medicine cabinet is dangerous. Even antibiotics that overlap between human and veterinary medicine come in doses formulated for people, and cats metabolize drugs differently. The wrong antibiotic or wrong dose can cause liver failure, kidney failure, seizures, or worse.
First-Line Antibiotics for Cats
Veterinarians reach for a handful of antibiotics most often because they’re effective against common infections and relatively safe for cats. These are considered first-line treatments, meaning they can be prescribed based on the type of infection without necessarily needing lab testing first.
Amoxicillin-clavulanate is one of the most widely prescribed antibiotics in feline medicine. It’s a penicillin-type drug paired with a compound that helps it work against bacteria that would otherwise resist it. It treats skin infections, wounds, abscesses, cellulitis, and urinary tract infections. For skin issues, treatment typically lasts 5 to 7 days or until 48 hours after symptoms clear, whichever is shorter. Urinary tract infections often require 10 to 14 days. Your vet will reassess if there’s no improvement within 3 days.
Cephalexin is a first-generation cephalosporin, closely related to penicillins. It’s a go-to for skin infections caused by staph bacteria and is generally well tolerated. It’s given orally, usually twice daily.
Metronidazole works against anaerobic bacteria (the kind that thrive without oxygen) and certain parasites. Vets commonly prescribe it for gastrointestinal infections and inflammatory bowel conditions. It’s effective, but it does carry a notable risk: at high doses or with prolonged use, it can cause neurological problems including disorientation, loss of coordination, tremors, and even collapse. These signs have been documented in cats receiving doses at or above the upper end of the typical range for extended periods. Most cats on standard short courses do fine, but watch for any sudden clumsiness or behavior changes.
Antibiotics for Dental and Bone Infections
Clindamycin stands out for infections in the mouth, bones, and joints because it penetrates well into those tissues. It’s labeled for treating bacterial infections of the skin, soft tissue, periodontal tissue, and bone in cats. Dental abscesses and deep wound infections are common reasons a vet might choose it. Cats typically receive it once daily by mouth.
For skin infections specifically, clindamycin is considered a second choice behind cephalexin. If the bacteria turn out to be resistant to first-line drugs, your vet may run a culture and sensitivity test before switching to clindamycin.
Doxycycline and the Pill Problem
Doxycycline, a tetracycline antibiotic, is commonly used for respiratory infections, tick-borne diseases, and certain bacterial infections that don’t respond to simpler drugs. It’s effective, but it comes with a well-known hazard in cats: esophageal damage.
Pills and capsules can easily lodge in a cat’s esophagus. When a doxycycline tablet gets stuck, it can cause severe inflammation and scarring that narrows the esophagus permanently. This risk applies to clindamycin tablets too. The standard prevention is simple: always follow a doxycycline pill with a small syringe of water or a bit of wet food to make sure it reaches the stomach. Liquid formulations, when available, are often safer for cats.
Fluoroquinolones and Vision Risks
Fluoroquinolones like enrofloxacin, marbofloxacin, and orbifloxacin are powerful antibiotics reserved for more serious or resistant infections. They require culture and sensitivity testing before use, meaning your vet needs to confirm which bacteria are present and that the infection won’t respond to safer first-line drugs.
Enrofloxacin carries a specific and serious risk in cats: retinal toxicity. After it was approved for flexible dosing in cats, veterinarians reported cases of blindness, partial blindness, and dilated pupils. Research confirmed these effects are dose-related. Cats given the lowest approved dose (5 mg/kg per day) showed no eye changes, while higher doses caused visible retinal damage within just 3 days. At the highest experimental doses, cats developed a progression of retinal changes including graying of the central visual area, blood vessel narrowing, and widespread retinal damage within a week. When fluoroquinolones are truly needed, vets use the lowest effective dose and monitor closely.
Long-Acting Injectable Antibiotics
Cefovecin is an injectable cephalosporin sold under the brand name Convenia. A single injection maintains effective drug levels for approximately 7 days against target bacteria like Pasteurella, which commonly causes wound infections and abscesses in cats. It’s especially useful for cats that are difficult to medicate orally, since one vet visit replaces a week of twice-daily pills.
The convenience comes with a tradeoff: once injected, you can’t stop the drug if your cat has a bad reaction. With oral medications, you simply stop giving them. Cefovecin is classified as a second-line antibiotic, so it’s typically used when oral options aren’t practical rather than as a default first choice.
Why Antibiotic Selection Matters
Veterinary guidelines organize antibiotics into tiers specifically to slow the development of resistant bacteria. First-line drugs handle the majority of routine infections. Second-line drugs require proof, through bacterial culture, that the infection won’t respond to simpler options. Third-line or “last resort” antibiotics like carbapenems and vancomycin are reserved for rare, life-threatening infections where nothing else works.
This isn’t just bureaucratic caution. Resistant bacteria, including MRSA and certain strains of E. coli that produce enzymes breaking down common antibiotics, have been identified in veterinary settings. Every time a powerful antibiotic is used unnecessarily, it increases the chance that bacteria evolve to survive it.
Common Side Effects to Watch For
Most cats on antibiotics experience mild gastrointestinal effects: decreased appetite, nausea, vomiting, or diarrhea. These are common across nearly all antibiotic classes because the drugs don’t distinguish between harmful bacteria and the beneficial bacteria in your cat’s gut.
Probiotics can help. Giving a veterinary probiotic during and after antibiotic treatment supports recovery of normal gut bacteria and may reduce diarrhea, nausea, and appetite loss. The key detail: space the probiotic at least two hours apart from the antibiotic dose, so the antibiotic doesn’t immediately kill the beneficial bacteria you’re trying to introduce.
More serious reactions, though uncommon, include drooling, tremors, or seizures. These can signal toxicity or an allergic response and warrant immediate veterinary attention.
Human Antibiotics Are Not Safe Substitutes
Some of the same antibiotic compounds used in veterinary medicine also exist in human formulations, which leads people to wonder if they can skip the vet visit. This is risky for several reasons. Human tablets are dosed for a 150-plus-pound adult, not an 8-pound cat. The inactive ingredients in human formulations may include compounds toxic to cats. And certain human antibiotics, such as isoniazid (used for tuberculosis), are outright poisonous to cats.
Signs of antibiotic toxicity in cats include drooling, vomiting, diarrhea, loss of appetite, tooth discoloration, liver or kidney failure, and seizures. If your cat accidentally ingests a human antibiotic, contact a veterinary poison control service immediately.