Antibiotics for dental disease in dogs and cats:when they are needed and when they are not

Why an antibiotic will not cure periodontitis

Periodontitis is inflammation of the tissues that hold the tooth in place: the gums, the ligament and the bone around the root. It is caused by plaque (a biofilm — a sticky community of bacteria on the tooth surface) and tartar, which build up above and below the gum line. More in Periodontal disease in dogs and Periodontal disease in cats.

Bacteria in a biofilm are shielded by it, and antibiotics act on them much less effectively than on free-floating bacteria. Tartar is a mineralised deposit: medicines do not dissolve it. And bone that inflammation has already destroyed is not restored by an antibiotic.

So during a course the breath may improve and the gums may bleed less. But as soon as the course ends, bacteria recolonise the pockets around the teeth and the inflammation returns. The only way to break the cycle is mechanical cleaning above and below the gum line — scaling of the oral cavity under anaesthesia as part of COHAT, with dental radiography — plus daily home care.

I show how bacteria from the gums reach the bloodstream, and why the mouth is linked to the whole body, on a diagram in How a dog’s and cat’s mouth works.

Abscesses and infected teeth: why medicine does not reach the source

When a tooth fractures and exposes the pulp (the living core of the tooth with its nerves and blood vessels), or the pulp dies after a knock, dead tissue full of bacteria is left inside the tooth. There are no working blood vessels there any more, and an antibiotic reaches tissues through the blood — so it barely gets inside such a tooth. Medicines also penetrate poorly into an abscess (a collection of pus).

Hence the typical story: a swelling under the eye or on the jaw goes down during the course and then comes back. The source — the dead pulp or the affected root — has not gone anywhere. Only treating the tooth removes it: root canal treatment (removing the dead pulp and sealing the canal) or extraction. More in the articles on pulpitis and swelling under the eye.

In some conditions an antibiotic is simply aimed at the wrong target. Tooth resorption (TR) is not an infection: the body itself breaks down the tooth tissue. Chronic gingivostomatitis in cats is inflammation in which an exaggerated immune response plays a major role; an antibiotic may dampen it for a while but does not solve the problem. And a fractured tooth hurts because of the exposed pulp, a pain an antibiotic does not relieve.

When antibiotics really are needed

Antibiotics are important medicines, and there are situations where they cannot be done without. The vet decides after an examination. Most often these are:

• The infection is spreading. Swelling of the face or neck is growing quickly and the tissues are hot and painful — signs of diffuse soft-tissue infection (cellulitis). Or the infection has reached the jawbone (osteomyelitis).
• There are signs of illness throughout the body: a raised temperature, lethargy, refusing food alongside an infection in the mouth.
• The patient has particular risk factors: a weakened immune system (for example, due to chemotherapy or long-term immunosuppressive medicines) or serious concurrent disease where the vet judges the risk of infection to be high.
• Certain surgical situations: for example, an open jaw fracture where the bone is exposed to the bacteria in the mouth, or surgery in an area with marked infection in the bone.

Even then, the antibiotic is part of the plan, not a replacement for treatment. It helps contain the infection and stabilise the pet, but the source — the diseased tooth, a deep pocket, a retained root fragment — still has to be removed. If the patient is in a risk group, the vet may give the antibiotic during the procedure itself, when bacteria from the mouth enter the bloodstream, instead of a course of tablets beforehand.

If an infection does not respond to treatment or keeps coming back, the vet may take a sample for bacterial culture — a test that shows which bacteria are present and which antibiotics they are sensitive to — so that the medicine can be targeted.

“A course of antibiotics first, then the dental”: why this is usually not treatment

Owners are sometimes told to “give a course of antibiotics first to settle the gums” and do the dental afterwards. The reasoning is understandable: the gums are red and bleeding and the breath smells. But the inflammation is caused by plaque and tartar, and while they are on the teeth, a course only buys a pause.

So instead of “a week’s course” I recommend a different order: from diagnosis straight to treating the cause. If a particular pet does need an antibiotic, we will decide when and how to give it. I set out what this plan looks like in the final section.

Antibiotic resistance: why “just in case” does harm

Antibiotic resistance is the ability of bacteria to survive antibiotics. Each course kills the sensitive bacteria, while those that survive multiply and can pass their resistance on to others. A course does not act only in the mouth: it affects the bacteria of the gut and skin throughout the body.

The more often a pet receives antibiotics it does not need, the higher the risk that one day, when an infection is truly serious — after a jaw injury or surgery — the usual medicine will not work. Resistant bacteria can also pass between animals and the people they live with. That is why veterinary guidelines call for antibiotics to be prescribed only when there is a clear benefit.

Antibiotics also have side effects of their own: vomiting, diarrhoea, loss of appetite, allergic reactions. Some tablets can irritate a cat’s oesophagus if they get stuck there — which is why the vet explains exactly how to give them.

Why you should not give leftover or human antibiotics

A medicine cabinet with whatever is “left over from last time” can seem like a handy solution. But it is risky for several reasons:

• Wrong drug. Antibiotics act on different groups of bacteria and penetrate tissues differently. A medicine that helped with a skin or bladder infection may not work against the bacteria in the mouth.
• Wrong amount. Leftovers are usually not enough for a course, and human tablets are made for a different body weight and metabolism.
• Wrong patient. Some antibiotics carry special restrictions and risks for cats. Human syrups and chewable tablets may contain the sweetener xylitol, which is toxic to dogs.
• A hidden picture. A self-started course dampens the signs without curing anything. When the pet reaches the vet, its condition is harder to assess and a bacterial culture may be uninformative.
• Delayed treatment. While the pet is “on antibiotics”, the tooth and gums keep deteriorating.

One more thing: an antibiotic does not relieve pain. If your pet is in pain, what helps is pain relief prescribed by the vet and treatment of the cause — see Pain relief for toothache in dogs and cats. Why ointments, gels and repeated courses of medicine only mask the problem, I explain in detail in Why ointments, sprays and gels don’t treat diseased teeth.

If the vet has prescribed an antibiotic: how to give it properly

When an antibiotic is genuinely needed, it matters that it works and does no harm:

• give the medicine at the prescribed times and for exactly as many days as the vet said — do not shorten or extend the course yourself;
• if your pet spits out a tablet, you miss a dose or it will not let you give it — do not just stop, ask the vet what to do;
• vomiting, diarrhoea, itching, facial swelling or lethargy are a reason to contact the vet the same day;
• do not keep leftovers “for later” or give them to another animal;
• remember that the course does not cancel the planned treatment of the tooth.

What treats the cause: a plan instead of “one more course”

The cycle of “antibiotic — improvement — worse again” can only be broken by treating the source of the infection. This is what that looks like:

If you are not in Kyiv, you can start with an online consultation: I will look at your photos, help you judge how urgent it is and advise on the next steps.

1. 01

   Examination and consultation

   I assess the teeth, gums, any swelling and your pet’s general condition, decide whether an antibiotic is needed now and plan the pre-anaesthetic tests.

2. 02

   Pre-anaesthetic tests

   Blood tests and other investigations as clinically indicated — to prepare your pet for anaesthesia and reduce its risks.

3. 03

   COHAT under anaesthesia

   Examination and probing of every tooth, dental radiography, and scaling of the oral cavity above and below the gum line.

4. 04

   Treating affected teeth

   Root canal treatment, extraction or other procedures under the same anaesthetic — this is how we remove the source of infection.

5. 05

   Home care and follow-up

   Pain relief as prescribed, an antibiotic only if it is needed, daily toothbrushing and a follow-up check.

Frequently asked questions