Amoxicillin for cats: Dosage and Safety

In this article:

• Uses
• Safety
• Dosage
• Alternatives
• Summary

In this article

• Uses
• Safety
• Dosage
• Alternatives
• Summary

Amoxicillin is a bactericidal antibiotic commonly used in cats and dogs. It’s related to penicillin, but animals absorb it more readily, and the medication remains active longer. Amoxicillin, penicillin, and similar medications called beta-lactams kill bacteria by blocking their ability to make cell walls, but they don’t work against all bacteria. The U.S. Food and Drug Administration (FDA) approves amoxicillin for certain feline bacterial infections, including respiratory, urinary tract, skin, soft tissue, and intestinal infections. However, veterinarians may use it off-label for other types of bacterial infections. 

 

RELATED: Discount pet meds & resources

What is amoxicillin used for in cats?

Veterinarians use amoxicillin to eradicate bacterial infections in cats. According to its prescribing label, the FDA has approved amoxicillin to treat certain bacterial infections of the respiratory tract, digestive system, skin, soft tissues, and urinary tract. 

Amoxicillin cannot fight off every type of bacterial infection. Its spectrum of activity is particularly strong against anaerobic bacteria that don’t need oxygen. Provided they haven’t developed resistance to beta-lactam medications such as amoxicillin. Some drug-resistant infections will require amoxicillin combined with clavulanate, such as Augmentin. 

Urinary tract infections

Urinary tract infections (UTIs), particularly bladder infections, often involve bacteria susceptible to amoxicillin, such as Staphylococcus, Streptococcus, and E. coli. Still, amoxicillin can’t treat every infection, so veterinarians predict the likely bacteria and select an appropriate antibiotic based on the specifics of the case. 

Gastrointestinal infections

Many bacteria that cause UTIs normally live harmlessly in the intestines, but they can sometimes cause problems there, too. Amoxicillin can treat infections caused by susceptible bacteria. Some cats are also infected with a type of stomach bacteria called Helicobacter. Veterinarians remain uncertain about Helicobacter’s role in feline gastritis, though the infection may sometimes irritate the stomach lining. Veterinarians may prescribe amoxicillin or another antibiotic off-label for cats with signs of stomach irritation or ulcers, such as chronic vomiting or loss of appetite. 

Upper respiratory tract infections

Some upper respiratory tract infections in cats are caused by bacteria that respond to amoxicillin. This may include less common conditions, such as tonsillitis and tracheobronchitis, which often develop after a viral infection, dental disease, or airway irritation. A veterinarian may prescribe amoxicillin or another antibiotic based on the most likely bacteria and current veterinary guidelines. Repeated infections may require testing to identify the exact bacteria involved. 

Skin and soft tissue infections

Staphylococcus and Streptococcus species often cause skin and soft tissue infections in cats, including bacterial dermatitis, abscesses, lacerations, and wounds. Both respond to amoxicillin. Because these bacteria are so common, veterinarians may treat skin infections with amoxicillin-clavulanate, based on severity and clinical signs. If the antibiotic doesn’t work, they’ll test a sample. 

Is amoxicillin safe for cats?

Penicillins, such as amoxicillin, are among the most commonly used antibiotics in dogs and cats. Amoxicillin is effective, generally safe, well-studied, and has few side effects. Its main drawback is the potential to provoke an allergic reaction, as with any antibiotic. Cats that have had any allergic reaction to penicillin or other penicillin antibiotics should not be given amoxicillin. Cats that have reacted to medications similar to amoxicillin may also react to amoxicillin itself. Tell the veterinarian about any allergic reaction a cat has had to past medications. Cats with sepsis, shock, or severe illness should not be given oral antibiotics. They may be too sick to absorb the medication, so injections are needed.

Side effects of amoxicillin in cats

The most common side effects of amoxicillin in cats are:

• Loss of appetite
• Vomiting
• Diarrhea

The most severe adverse reactions are allergic. A mild reaction might cause hives, rashes, or itching. These aren’t life-threatening, but you should still stop amoxicillin and call the veterinarian. It may help to photograph the rash or welts.

Penicillins can also trigger anaphylaxis, an uncommon but potentially life-threatening allergic reaction. It causes a sudden drop in blood pressure and swelling that can close off the throat and airways. Symptoms appear shortly after a dose is given and can worsen rapidly. These include:

• Skin swelling
• Difficulty breathing (wheezing, rapid breathing)
• Weak but rapid pulse
• Acting dizzy
• Fainting

Anaphylaxis is a veterinary emergency. Take the cat to an open veterinary clinic or hospital immediately. 

Interactions of amoxicillin with other pet meds

As with any medication, problems can arise when amoxicillin is combined with other medications, but its list of interactions is short. Veterinarians are most concerned about combining it with:

• Antibiotics that stop bacteria from growing rather than killing them, such as macrolide antibiotics, tetracyclines, and sulfa drugs
• The anticancer medication methotrexate

If you give your cat dietary supplements, herbal remedies, or over-the-counter medications such as CBD, you probably don’t need to stop them while the cat is on amoxicillin. Still, check with the veterinarian first.

RELATED: Save on common antibiotics

Amoxicillin dosage for cats

The amoxicillin dosage for cats varies by infection, in both amount and duration. For most susceptible infections, the recommended dose is 50 mg per cat, or 10-22 mg/kg of body weight (about 5-10 mg/lb), given two to three times a day. Treatment usually lasts five to seven days, or as long as symptoms persist, plus two days after they resolve.

To set the right dose, veterinarians distinguish between gram-positive and gram-negative bacteria, which have structurally different cell walls. Penicillins work on both, but doses may need to be higher for gram-negative infections.

Plumb’s Veterinary Drug Manual lists the following amoxicillin dosages for cats:

• For susceptible gram-positive bacterial infections: 10 mg/kg by mouth, 2-3 times per day
• For susceptible gram-negative bacterial infections: 10-22 mg/kg by mouth, 2-3 times per day
• For susceptible UTIs: 11-15 mg/kg by mouth, every 8-12 hours for 3-5 days
• For Helicobacter eradication: 20 mg/kg by mouth, twice a day for 14 days, combined with the antibiotics metronidazole and clarithromycin
• For sepsis: 22-30 mg/kg by injection or by mouth, every 8 hours for as long as necessary

Can cats overdose on amoxicillin?

Too much amoxicillin isn’t usually a health threat, but it can cause digestive problems such as vomiting, diarrhea, or loss of appetite. If a cat gets too much, call a veterinarian, veterinary hospital, or animal poison control center for advice. 

Can I give my cat amoxicillin every day?

Cats can be given amoxicillin every day for a few days. It’s safe when given exactly as the veterinarian prescribes.

Give every dose on time for the full prescribed course. Missed doses allow bacteria to grow back and possibly develop resistance to amoxicillin. Stopping early can let the infection return.

Long-term use carries its own risks. Amoxicillin affects bacterial colonies throughout the body, most of which are beneficial. Overusing an antibiotic disrupts that balance and can lead to serious infections. It also raises the risk of bacteria mutating into drug-resistant forms.

How to give your cat amoxicillin

The veterinarian will send caregivers home with amoxicillin tablets or a liquid formulation made for cats, such as brand-name Amoxi-Tabs or Amoxi-Drops. Give human formulations of amoxicillin only under a veterinary professional’s direction.

• Follow all the veterinarian’s instructions.
• Don’t miss doses.
  • Give every dose on schedule for the full course, even if the cat seems fully recovered.
• Amoxicillin can be given with or without food.
  • If the cat vomits or shows other signs of digestive upset after a dose, give it with food.
• If you’re unsure how to give a tablet, ask a veterinary professional to show you. Or ask for a liquid version, which can be easier to dose.
• When giving the liquid suspension:
  • Shake the bottle before each dose to mix the medication evenly.
  • Measure each dose with a calibrated oral syringe.
  • The oral suspension is only good for 14 days — throw out any that’s left after that.
• If you miss a dose, give it when you remember, unless it’s almost time for the next one. Then skip the missed dose and continue as scheduled.
• There’s no need to taper the dose when stopping amoxicillin.
• Store amoxicillin tablets at room temperature.
• The oral suspension can be stored at room temperature or in a refrigerator.

Amoxicillin alternatives for cats

With many antibiotics available, the veterinarian’s job is to choose the safest, most effective one for the bacteria causing the infection. Amoxicillin is broad-spectrum, meaning it fights a wide range of bacterial infections, so it’s often a good first choice.

Sometimes, amoxicillin doesn’t work because the bacteria produce an enzyme that disables part of the amoxicillin molecule. In that case, the veterinarian will prescribe amoxicillin-clavulanate, a combination that blocks the enzyme.

Some cats can’t take penicillin safely. For these cats, a veterinarian can use antibiotics similar to amoxicillin, called beta-lactams, which include cephalosporins, carbapenems, and others. Depending on the infection, other antibiotics might work as alternatives, such as macrolides, sulfa drugs, or doxycycline.

Because of the risks, veterinarians are unlikely to suggest natural remedies for bacterial infections.

RELATED: Amoxicillin (Amoxil) alternatives: what can I take instead of amoxicillin?

Summary

Amoxicillin for cats is effective and safe when all the veterinarian’s instructions are followed. For it to work, give every dose for the full course of the prescription. Sometimes, amoxicillin still won’t work. Contact the veterinarian if the cat doesn’t improve after a few days.