Amoxicillin Allergies in Dogs

Amoxicillin is a penicillin antibiotic that is used to treat bacterial infection in dogs as well as humans. Penicillins are a beta-lactam antibiotic that kill bacteria by inhibiting their ability to form a cell wall. Amoxicillin is used to treat infections of the respiratory and gastrointestinal tract, as well as the genitourinary system, skin and soft tissue abscesses. It targets staphylococcus aureus, streptococcus species, E. coli, and Proteus mirabilis among other organisms. Bacteria that produce beta-lactamase will not be affected by amoxicillin, however a combination medicine containing amoxicillin and clavulanic acid (a beta-lactamase inhibitor) may get around this drawback.

Some side-effects like vomiting and diarrhea are fairly common with amoxicillin. Allergic reaction is rarer, but can be more serious. As a penicillin, amoxicillin is one of the antibiotics most likely to cause an allergic reaction, although this is still extremely rare in dogs. Symptoms are typically limited to rash and watery eyes, but serious a life-threatening anaphylaxis is possible. Dogs that have had a prior reaction to another penicillin antibiotic should not take amoxicillin. Other beta-lactam antibiotics, like cephalosporins and cephamycins, should also be avoided, depending on the advice of a veterinarian. If your dog has had a reaction to amoxicillin, or another penicillin, you should mention this to the veterinarian any time an antibiotic is prescribed.

Amoxicillin is a common broad-spectrum antibiotic that is prescribed to dogs for a number of different infections. Penicillin antibiotics, like amoxicillin, have one of the highest rates of allergic reaction in sensitive individuals. Serious reactions are rare, but can be life-threatening.

Watch for these symptoms if your dog has just started taking amoxicillin.

• Rash (maculopapular lesions)
• Redness (erythroderma)
• Other types of skin lesion (blisters or scaling skin)
• Itchiness (pruritus)
• Incessant scratching
• Watery eyes
• Runny nose
• Swelling and hives (urticaria-angioedema)
• Purple rash caused by bleeding into the dermal tissue (purpura)
• Anaphylactic shock (rare) (vomiting, diarrhea, difficulty breathing, collapse, death)

Types

There are number of different brand-name amoxicillin medications that deliver the antibiotic in the following ways.

• Tablets or drops – recommended dose is approximately 10-20 mg/kg twice daily
• Injection – recommended dose is 4-10 mg/kg once or twice a day
• Combination tablet with amoxicillin and a beta lactamase inhibitor – recommended dose 10—20mg/kg twice daily

It is not known why some dogs have allergic reactions while others do not. You should look for symptoms of amoxicillin allergies in the following cases.

• Starting amoxicillin treatment for an infection
• Known sensitivity to penicillin or another beta-lactam antibiotic
• General tendency to severe allergic reactions

An amoxicillin allergy will be diagnosed if your dog exhibits symptoms after beginning an amoxicillin regimen, and confirmed if the symptoms resolve themselves when the medication is discontinued. A previous allergic reaction to penicillin or another beta-lactam antibiotics would also be a reason to suspect amoxicillin allergies and avoid the drug. You should always mention previous drug reactions whenever a new medication is prescribed. It’s also a good idea to read through the side-effects and possible responses, so you know what to look for in your dog. If your dog exhibits unusual symptoms after starting amoxicillin or another medication, call the veterinarian and ask for advice. Severe symptoms like excessive swelling, trouble breathing, or collapse should be treated as an emergency.

If your dog’s symptoms suggest an allergic reaction, the veterinarian will recommend you discontinue taking amoxicillin immediately. Mild symptoms will clear up without further treatment, but the veterinarian may need to prescribe a different antibiotic to fight the original infection.

Severe rashes with blistering and broken skin may need to be treated with topical ointments to prevent further infection. Antihistamines and corticosteroids could also be prescribed to calm the immune system and reduce symptoms.

Dogs with anaphylaxis should be given an epinephrine injection immediately. If you have a dog Epipen at your house, this will help, but your dog will still need immediate treatment. Other emergency measures like additional oxygen, intravenous fluids, and even blood transfusion could be necessary to save your dog’s life. Your dog will need to stay in a veterinary hospital for a day or two until the symptoms have passed and all systems are functioning normally.

Serious allergic reactions to amoxicillin are rare, and most dogs will make a complete recovery with veterinary treatment. There is no cure for an amoxicillin allergy however, so your dog will need to avoid amoxicillin and other penicillin antibiotics throughout his life. Make sure information about your dog’s allergies is stored in his medical file and mention them specifically anytime you are working with a new veterinarian. Even if your dog hasn’t experienced an allergic reaction, it’s a good idea to watch for symptoms anytime a new medication is started. If your dog has experienced an anaphylactic reaction to a drug or any other allergen, discuss getting a dog Epipen with your veterinarian. An immediate injection administered at home can help your dog survive long enough to get treatment.