Doxycycline for Dogs: Uses, Side Effects, and Alternatives

Most dogs take antibiotics at least once in their lives to treat a current infection or prevent a new infection. One of the antibiotics commonly used in veterinary medicine is doxycycline. Your veterinarian may prescribe this medication to treat various bacterial infections.

Since the use of doxycycline for dogs is “off-label,” it’s important to know about the medication’s side effects, in addition to following your veterinarian’s advice, which may differ from what’s on the product label. Read on to learn about the proper uses of doxycycline for dogs, potential side effects, drug interactions, and alternatives if your dog is pregnant or has a history of allergic reactions to medication.

What Is Doxycycline and How Does It Work?

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Like us, dogs routinely encounter bacteria on their skin and everyday surfaces, including their beds and water bowls. When a dog’s immune system isn’t working properly, bacteria can grow and multiply, leading to illness or infection. In such instances, your veterinarian may prescribe an antibiotic to kill the bacteria or stop them from growing.

Aside from bacteria, there are other kinds of microorganisms or microbes, which refer to living organisms that can only be seen under a microscope. These microorganisms include viruses and fungi. While some microbes are beneficial, such as the ones that aid in digestion or the making of cheese and yogurt, others can cause disease.

Doxycycline belongs to a class of medications called tetracyclines, which are classified as protein synthesis inhibitor antibiotics. Think of it this way. Cells, including single-celled organisms like bacteria, need to make proteins (protein synthesis) to grow. Doxycycline (antibiotic) works by preventing bacteria (inhibitor) from making proteins that are necessary for their survival. In addition, it compromises the bacteria’s cell walls and their ability to grow and replicate.

Doxycycline is what’s known as a broad-spectrum antibiotic, meaning it’s used to treat a wide range of bacterial infections. For example, doxycycline can target disease-causing bacteria such as the following:

• E.coli. Found in the intestines, E.coli can cause illness in puppies, seniors, and other immunocompromised dogs.
• Serratia. These bacteria can present on household items, including the pink slime that collects in water bowls. Serratia can cause skin infections and urinary tract infections.
• Pseudomonas aeruginosa. Found in soil, water, and decaying organic matter, pseudomonas aeruginosa can infect the skin and ears of dogs with a weakened immune system.
• Klebsiella. Transmitted from humans to animals through feces or direct contact, these bacteria can cause a respiratory infection or urinary tract infection.
• These bacteria may cause an abscess or pneumonia.

What Are the Uses of Doxycycline for Dogs?

Doxycycline is used off-label or extra-label. This means “it’s prescribed in a way that’s not listed on the FDA (Food and Drug Administration) label, such as using the medication for a different indicated species, dosage, or condition,” says Dr. Kelly Hood, DVM, veterinary expert at HonestPet.

She explains that off-label use of medications is a routine practice in veterinary medicine, when evidence and experience show that it’s a safe and effective treatment. “As always, it’s important to understand the risks and monitor for any side effects such as nausea, vomiting, diarrhea, or loss of appetite,” she adds.

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Compounded Formulations

Doxycycline is a partially synthetic drug, which means it’s derived from a naturally occurring source. “Compounded doxycycline is made by a specialized pharmacy into a non-commercially available formulation for one specific patient,” Dr. Hood says. “Sometimes shelf life can be affected by compounding.” Her advice is to confirm that the compounding pharmacy is reputable to ensure the product is safe, potent, and stable.

Since many veterinary patients are smaller than humans, “formulating the medication into a smaller pill size or a liquid is sometimes needed to get the right dosage,” she says. Some dogs aren’t very cooperative when it comes to taking pills. Giving them a compounded version that’s flavored or prepared as a liquid can be helpful.

Bacterial Infections

Doxycycline for dogs is used to treat bacterial infections. However, this drug isn’t effective against viral or fungal infections. Your vet may prescribe doxycycline to treat a current infection or prevent a secondary bacterial infection.

For example, dogs with a viral infection such as canine parvovirus are more vulnerable to developing a secondary infection. This is because the first infection (parvovirus) tends to weaken the body’s natural defenses, making your dog more susceptible to a secondary infection, which could be bacterial or fungal. Veterinarians may use doxycycline to treat the following conditions:

• Respiratory infections
• Urinary tract infections
• Infected wounds
• Blood-borne infections
• Tick-borne illnesses such as Rocky Mountain Spotted Fever, Lyme disease, Ehrlichiosis, Leptospirosis

This isn’t an exhaustive list. Doxycycline has a broad range of applications and can help treat many different types of bacterial infections and microorganisms that cause illness in dogs.

How to Give Doxycycline to Dogs

Doxycycline has high bioavailability, meaning it’s easily absorbed by the body. The best way to give doxycycline to your dog is to follow your veterinarian’s instructions. Your vet has access to detailed scientific literature about doxycycline uses, side effects, dosages, and drug interactions that most owners don’t.

Sometimes, doxycycline can irritate your dog’s esophagus. If you’ve ever swallowed a pill without water, you know how it feels when it gets stuck in your throat. The same thing can happen with dogs. The more time a pill remains in contact with the lining of the esophagus, the greater the chance of issues like inflammation, scarring, ulcers, or narrowing of the esophagus. One way to prevent this is to avoid giving the pill dry (i.e., without food or water), Dr. Hood says.

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Instead, she recommends giving your dog doxycycline along with a small meal to prevent an upset stomach. “Avoid giving this medication with dairy or high-calcium foods,” she says. “Food does not reduce doxycycline absorption as much as older tetracyclines, but minerals can still bind to it.” That’s why she suggests waiting a few hours after administering doxycycline to give your dog any supplements containing minerals, which can affect the antibiotic’s absorption.

Moreover, it’s best to avoid giving your dog doxycycline right before bedtime. Once they’ve had a dose, make sure they stay upright for 10 to 15 minutes. “Follow every tablet or capsule with food or at least 6 to 8 mL of water for small dogs, and more for larger dogs,” she says. “As well, there are liquid options if your dog has trouble swallowing pills.”

Consult the label for advice on how to store doxycycline properly. For example, oral formulations should be kept at room temperature, away from moisture and sunlight. Compounded medications may have different storage requirements.

Side Effects of Doxycycline for Dogs

Although dogs generally tolerate doxycycline well, it’s important to understand the possible side effects before giving your dog a new medication. The most common side effects are gastrointestinal (GI) symptoms, such as vomiting, diarrhea, and loss of appetite. Severe GI symptoms could be a sign of a doxycycline overdose, in which case you should call your vet immediately or contact a pet poison helpline.

If your dog has a history of allergic reactions to antibiotics, especially those in the tetracycline family, make sure to mention this to your vet, as doxycycline could trigger a dangerous allergic reaction. Caution is also needed when using doxycycline in dogs with liver disease. While it may take several days to see an improvement in symptoms, make sure to call your vet if your dog’s condition worsens.

Moreover, tetracycline antibiotics like doxycycline can cause skeletal limb deformities in developing puppies in utero, posing a potential risk to pregnant dogs. In some cases, the benefits of using doxycycline outweigh the potential risks for pregnant dogs. Regardless, be sure to let your vet know if your dog is pregnant before commencing treatment.

Tetracycline is used in the treatment of periodontal disease and heartworm disease, since it kills Wolbachia. These bacteria are needed by the heartworm host to survive. The downside is that tetracycline can discolor teeth, giving them a yellow appearance.

Depending on the type of infection, your vet may suggest alternative medications. For example, metronidazole is an antibiotic that’s used to treat diarrhea and inflammation of the large intestine. Another antibiotic, cephalexin, is used to treat ear infections and urinary tract infections. In any case, it’s best to discuss treatment options with your vet and determine which antibiotic is appropriate for your dog.

Doxycycline Drug Interactions

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Similar to way certain foods alter how a drug works, taking more than one medication at a time could lead to drug interactions. Sometimes, these interactions decrease a drug’s effectiveness or increase its potency, possibly triggering symptoms like dizziness or an elevated heart rate. For this reason, it’s important to tell your vet about all medicines and supplements your dog is taking, Dr. Hood emphasizes.

Even natural or herbal supplements can interact negatively with medications, including those available over the counter. Tell your vet if your dog is taking any of the following medications or supplements while on doxycycline:

• Oral antacids
• Multivitamins
• Bismuth subsalicylate (Pepto-Bismol)
• Kaolin-Pectin (a formulation that was once used in Kao-Pectate, a medication for treating diarrhea and upset stomach)
• Iron supplements
• Bactericidal (kill bacteria) antibiotics, such as penicillin, enrofloxacin, cephalosporin, or aminoglycosides which slow the growth of bacteria
• Anticoagulant medications like warfarin, which are used to prevent and treat blood clots
• Phenobarbital or phenytoin, which are used to treat seizures

If your dog is taking any of these drugs, it doesn’t necessarily mean they can’t take doxycycline. However, it may change the way you administer the drug. For instance, when giving your dog doxycycline, “separate minerals and supplements that contain calcium, magnesium, zinc, or iron by at least three hours,” she says. “And make sure not to give doxycycline at the same time as antacids, bismuth subsalicylate, kaolin pectin, or sucralfate.”

Drugs belonging to the tetracycline class, like doxycycline, can change the time it takes for blood to clot. Warfarin, sometimes referred to as a blood thinner, works by preventing blood clots. Dogs on warfarin may require additional monitoring or an adjustment of the dosage because it can interact with doxycycline.

Dosage of Doxycycline for Dogs

The dosage of doxycycline for dogs will vary depending on your dog’s health and condition. While the Merck Veterinary Manual recommends an oral dose of 5 to 10 mg/kg per day, you shouldn’t attempt to adjust the dosage without the guidance of your veterinarian. Changing your dog’s medication could lead to antibiotic resistance, which is dangerous for your dog and may also result in a longer recovery time.

If you forget to give your dog a dose of doxycycline, “give the missed dose when you remember, unless it’s very close to the next one,” Dr. Hood says. “If that’s the case, skip the missed dose and return to the regular schedule, since you don’t want to double up.” Contact your veterinarian if you miss more than one dose or if your dog doesn’t improve with treatment. Even if your dog is showing signs of recovery, make sure they finish the full course of the drug, unless your veterinarian tells you to discontinue use, she adds.