by David F. Kramer
Amoxicillin is an improved version of the antibiotic penicillin; touted for having a broader range of activity and being more resistant to stomach acids than naturally-occurring penicillin. The drug kills bacteria by disrupting the formation of their cell walls and is often prescribed by veterinarians to combat bacterial infections in pets.
“In my experience, amoxicillin is a safe antibiotic when appropriately prescribed by a veterinarian and used by the pet owner,” says Dr. Patrick Mahaney, of Los Angeles, CA. “Amoxicillin treats many common bacterial infections, including some of those affecting the mouth, respiratory tract, skin, urinary and digestive tracts, and others.”
Side Effects and Intolerance to Amoxicillin
“The most common side effect” of amoxicillin, Mahaney says, “is digestive tract upset.”
According to Mahaney, amoxicillin is not recommended for dogs that have previously exhibited clinical signs of intolerance or an allergic reaction. He says that intolerance can include signs such as digestive upset (vomiting, diarrhea, or lack of appetite), lethargy, or changes in behavior. Signs of an allergic response can include digestive upset, as well as skin reactions such as redness, swelling, or hives. A potentially fatal type of allergic reaction, called anaphylaxis, is also possible in rare cases and can cause difficulty breathing, low blood pressure, seizures and coma.
Any antibiotic can cause side effects, says Dr. Adam Denish of Rhawnhurst Animal Hospital in Elkins Park, PA. “I wouldn’t single out amoxicillin in general for negative interactions,” Denish says, “most [side effects] are just minor. However, it would be prudent to tell your veterinarian if any side effects occur. In some cases, we discontinue the drug or adjust the dose. However, it’s very important to not stop or start any types of medicine without discussing it with your pet’s doctor.”
Human Amoxicillin Not the Same as Pet Amoxicillin
If your dog requires amoxicillin or a similar antibiotic to treat an infection, says Dr. Mahaney, veterinary-specific medicines are the best option. The dangers of giving your dog human-grade amoxicillin, he says, include the potential to expose your dog to components of the drug that are “inappropriate” or “potentially toxic.”
Some of these ingredients, says Mahaney, include artificial flavors, colors, and chemical preservatives. Pet owners also need to be on the lookout for xylitol in medications, Mahaney says. Xylitol is a sugar substitute that can be toxic to dogs. A veterinary-specific version of amoxicillin will also help with proper dosing, he says, although the exact dosage will still be a determination made by your veterinarian, who is best acquainted with your pet’s health history.
Overuse of Antibiotics and the Rise of the ‘Super Bug’
According to a 2011 assessment study of practices at a small animal veterinary teaching hospital, from May 2008 to 2009 amoxicillin (in its various forms) was by far the most common antibiotic prescribed to treat confirmed or suspected bacterial infections.
As is the case with human antibiotics, the study suggested that veterinarians are also prone to over-prescribe these drugs. In only 17% of the instances in which antibiotics were prescribed was there a confirmed infection. Forty-five percent of the cases met the criteria for a “suspected” infection while in the remaining 38% there was no documented evidence for infection. These prescribing practices can have unintended consequences, says Denish.
“Just as in human medicine, there is a significant problem with antibiotic resistance in the animal world. There are many factors that can lead to antibiotic resistance. One that is within our control is the overuse of antibiotics,” says Denish.
“This can be due to veterinarians prescribing antibiotics when they’re not needed, or owners not using these drugs as prescribed,” he explains. “Improper sterilization and cleaning processes and increasing numbers of sick animals in hospitals can also lead to the creation of ‘super bugs.’ These are bacteria that have become immune to a majority of commonly used antibiotics,” says Denish.
“At least a few times a week, I receive culture results that show that a particular animal has an infection that is resistant to the normal antibiotic protocols,” says Denish. “If we gave a stronger dose, or extended the length of treatment, that would definitely not help the problem—in fact, it would make it worse.”
With antibiotic resistance, those bacteria can take over the body and cause more damage, leading to a worsening of the condition” says Denish, adding that, “in severe cases, it can lead to death.”
One way vets can ensure prescribing the right antibiotic for a dog’s infection is to call for a “sensitivity profile,” says Denish. “When your vet performs a test to find out which bacteria is causing a problem, he will also receive a sensitivity profile. That tells him which antibiotic will work for that particular infection.” While this test does cost owners money at the offset, it prevents the cost and dangers associated with prescribing antibiotics that turn out to be ineffective in the end.
Getting the Best Results from Amoxicillin
“I generally use a combination of amoxicillin and another agent which improves the drug’s effects, called clavulanic acid,” says Mahaney. The combination of amoxicillin and clavulanic acid is called Clavamox in the veterinary world, he explains, and is available in both liquid and tablet form for your pet. Generic and human formulations are also available.
“Medium and large dogs both generally take the tablets, but some smaller dogs can take the tablets too. These tablets can be hidden in a moist treat, or directly inserted into the back of the mouth with a finger or pet-appropriate ‘pilling’ device.” Liquid amoxicillin-clavulanic acid can be a good option for some cats and very small dogs.
Alternatives to Antibiotics
“Some mild bacterial infections can resolve without the use of antibiotic therapy,” says Mahaney. “Ideally, the body will mount a sufficient immune response to manage or resolve the infection.”
Depending upon the type of infection that is affecting the pet, says Mahaney, other treatments, including warm compress or bathing, can promote blood flow to the site of infection and enhance the delivery of oxygen, nutrients, and white blood cells while speeding the removal of metabolic wastes and byproducts of the body’s attempt to fight infection. And then there are the alternative methods for combatting “bad” bacteria. “In my holistic veterinary practice, I use a cold laser with a bacteria-killing blue light to promote tissue healing,” says Mahaney.
This article was verified and edited for accuracy by Dr. Jennifer Coates, DVM
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