Antibiotics For Dogs: Uses, Side Effects & Safety

Despite our best efforts to maintain their health—from ensuring a balanced diet to administering regular preventative medications—our beloved pups can still fall prey to illness. Bacterial infections, in particular, are a recurring challenge.

When bacterial infections arise, antibiotics play a crucial role in helping our dogs recover and regain their usual liveliness. But what are antibiotics for dogs, and how do they work?

In this blog post, we’ll take a closer look at dog antibiotics, exploring the most common types, their uses, potential side effects, and more. Moreover, we'll shed light on the safety measures essential to antibiotic use in dogs to prevent complications like antibiotic resistance.

• What Are Antibiotics & How Do They Work?
• Most Common Antibiotics For Dogs
• Uses: Antibiotics For Dogs
• What Are The Side Effects Of Antibiotics For Dogs?
• Antibiotic Safety
• FAQs
• Final Notes

What Are Antibiotics & How Do They Work?

Antibiotics, also known as antibacterials, are medications used to treat infectious diseases caused by bacteria and certain other microorganisms. They work by either killing bacteria or inhibiting their growth and replication. Antibiotics can be derived from natural sources, such as fungi and bacteria, or they can be synthesized in a laboratory.¹

To get an even better understanding of how antibiotics work in the veterinary world, let's start by exploring the step-by-step process vets follow when prescribing antibiotics. According to the Merck Veterinary Manual, successful antibiotic treatment is based on four key steps.²

1. Identifying what’s responsible for your pet’s infection and selecting the suitable antibiotic for treatment
2. Ensuring the antibiotic reaches effective levels at the site of infection for an adequate duration
3. Determining the appropriate dosage, frequency, and method of administration that optimizes the chances of safely curing the infection
4. Implementing supportive treatments to help your pet overcome the infection²

Having gained insight into a vet's decision-making process when prescribing antibiotics, you must also know that there are many different classes of antibiotics available for use in veterinary medicine.

While some are specially formulated for animals and FDA-approved for use in certain animals, others are prescribed off label or used for a different purpose than what is intended. As a general rule of thumb, always follow your vet’s exact instructions when administering antibiotics to your dog to ensure their health and safety.

Let’s take a look at the different classes of antibiotics used for dogs, focusing on their mechanisms of action and effectiveness against specific types of bacteria.

• Penicillins: The penicillin class includes commonly prescribed antibiotics for dogs, such as penicillin and amoxicillin. Penicillins work by interfering with the bacteria's cell wall synthesis, causing it to weaken and eventually die. They are specifically effective against streptococcal and clostridial infections, which are usually associated with health issues like pneumonia, urinary tract infections (UTIs), and hemorrhagic gastroenteritis.³
• Cephalosporins: Cephalosporins, such as cephalexin and ceftriaxone, have a similar mechanism of action to penicillins but are effective against a broader range of bacteria.³
• Cephamycins: Cephamycins are a subclass of cephalosporin antibiotics, so they also have a similar mechanism of action. Cephamycins, such as cefoxitin and cefotetan, are broad-spectrum antibiotics often used to treat skin and soft tissue infections, UTIs, respiratory tract infections, and some surgical site infections.³
• Aminoglycosides: Aminoglycosides inhibit bacterial protein synthesis, causing certain bacteria to stop growing and, in some cases, even leading to bacterial cell death. They are particularly effective against aerobic bacteria, including species like Escherichia coli, which are a common culprit of UTIs. However, this class of antibiotics for dogs is only reserved for severe infections due to its toxicity.³
• Fluoroquinolones: Enrofloxacin and ciprofloxacin are commonly used fluoroquinolone antibiotics for dogs. They work to fight infections by preventing bacteria from properly replicating their DNA and dividing. With a broad spectrum of activity, they can be used for pyoderma in dogs, wound infections, and more. Generally, they are not recommended for use in younger dogs, such as small to medium dogs under eight months of age.³
• Macrolides: Macrolide antibiotics used for dogs, like erythromycin and azithromycin, inhibit protein synthesis in bacteria as well, preventing them from multiplying. Unlike many of the broad-spectrum antibiotics we’ve mentioned already, macrolides have a much narrower application and are primarily used to treat mycoplasmosis and campylobacteriosis.³
• Tetracyclines: Tetracyclines, such as doxycycline and minocycline, are a class of dog antibiotics that also interfere with protein synthesis. They are commonly used to treat acne, Lyme disease, leptospirosis, and respiratory tract infections.³
• Sulfonamides: Sulfonamides, such as sulfadiazine, are general antibiotics for dogs used to treat UTIs, respiratory tract infections, gastrointestinal infections, and certain skin infections. They work by interfering with the synthesis of folic acid, which is necessary for bacterial growth and replication.³

These antibiotics used for dogs also come in a variety of formats and the format you choose will ultimately depend on your veterinarian's recommendation, the type of antibiotic your dog needs, and their preferences. You may receive antibiotics in the following forms:

• Tablets
• Chewable tablets
• Capsules
• Suspensions
• Injectable solutions
• Creams
• Ointments
• Sprays

Remember, for the health and safety of your furry companion, follow your vet’s instructions to a tee to prevent relapse, antibiotic resistance, and any other complications.

Most Common Antibiotics For Dogs

As we’ve mentioned, there are many types of antibiotics for dogs, each with their own specific characteristics. Some of the most common dog antibiotics include:

• Amoxicillin: Amoxicillin belongs to the penicillin class of antibiotics. Sometimes known by the brand name Moxatag, it works by stopping the growth and spread of bacteria. Available in the form of tablets, capsules, and oral suspensions, amoxicillin is a broad-spectrum antibiotic that is effective against a wide range of bacterial infections, including certain gastrointestinal infections, skin infections, and even tooth abscesses and dental infections caused by gum disease.⁴
• Amoxicillin and clavulanate acid: Amoxicillin and clavulanate acid, more commonly known by the brand name Clavamox, is a combination antibiotic for dogs. Because it features both amoxicillin and clavulanate acid, it’s particularly effective in treating stubborn, deep-seated infections, especially those resistant to other antibiotics. Clavamox is often used for skin infections, including wounds, abscesses, cellulitis, and dermatitis, but it can also be beneficial for bone infections and UTIs.⁵
• Cephalexin: Cephalexin, or Keflex, is another broad-spectrum antibiotic for dogs. It is most commonly used to treat infections of the skin, urinary tract, respiratory system, bones, and joints. This antibiotic should always be used with caution in dogs with kidney disease, and it is generally recommended to give cephalexin with food to help reduce the risk of stomach upset.⁶
• Enrofloxacin: Marketed as Baytril, enrofloxacin is an antibiotic used for dogs in the fluoroquinolones class. While it can be used to treat many bacterial infections throughout the body, including respiratory, urinary, gastrointestinal, and skin infections, dogs with a history of seizures and young, growing dogs should seek an alternative.⁷
• Doxycycline: Doxycycline inhibits the protein synthesis of bacteria, preventing their growth and multiplication. As a broad-spectrum antibiotic for dogs, it is effective against a wide range of bacteria. Generally, it is prescribed by vets for respiratory tract infections, but it can also be helpful in treating Lyme disease and certain eye infections.⁸
• Gentamicin: Gentamicin, also known as Gentak, differs from many of the antibiotics we've discussed as it is primarily administered in an injectable form or as eye drops and ear drops. In terms of safety, gentamicin should never be used in pregnant dogs, dogs with pre-existing kidney disease, or those with hearing problems.⁹
• Metronidazole: As the only antibiotic and antiprotozoal medication on this list, metronidazole, or Flagyl, Metrogel, and MetroCream, can treat both bacterial and parasitic infections in dogs. Interfering with the DNA synthesis of bacteria and parasites, it can be used in dogs with bacterial infections in their gastrointestinal tract, reproductive tract, and skin and soft tissues, as well as those affected by certain protozoal organisms, including Giardia and Trichomonas.¹⁰

With so many antibiotics available for dogs, how do you know which is the best one for your pup? Your vet will take the following factors into consideration when prescribing the most suitable antibiotic for your dog:

• Type of bacteria: Bacteria can be broadly divided into two categories—Gram positive and Gram negative. These two categories differ in their cell wall structure, the types of toxins they produce, and their resistance to antibiotics. If your dog’s bacterial infection is particularly worrying, your vet may send a sample to a lab to identify the specific type of bacteria involved. This way, they can prescribe a specific antibiotic to target the bacteria. For example, Gram-negative bacteria have an additional outer membrane, which acts as a barrier against certain antibiotics for dogs. Antibiotics such as enrofloxacin and gentamicin are more effective against this type of bacteria.
• Location of infection: Certain antibiotics used for dogs are better at reaching specific body systems than others. While some antibiotics may be better suited to treat skin issues, others are more effective for UTIs. Doxycycline, for example, is especially suited to reach the lungs, making it extra effective against respiratory system infections such as bronchitis, pneumonia, and kennel cough.
• Your dog’s current health condition: The age, weight, and overall health of your dog can also influence your vet’s choice of antibiotic. For instance, some antibiotics may be avoided in very young animals, old animals, or those with specific health conditions like kidney or liver disease.
• Side effects: All medications come with potential side effects. Your vet will take the specific side effects of certain antibiotics into consideration when choosing one for your dog.
• Drug interactions and resistance: The overuse of antibiotics can contribute to the development of antibiotic resistance. Additionally, if your dog is currently on medication, it is important to be cautious. Certain medications can cause antibiotics to become less effective and may even result in unexpected side effects. Your vet will carefully evaluate your dog’s medical history to prescribe the best antibiotic for them.
• Sensitivity test: In some cases, especially for severe or recurring infections, a bacterial culture and sensitivity test may be done. This involves growing the bacteria in a lab and testing different antibiotics against it to see which ones are most effective.

Overall, when your dog has a bacterial infection, it is crucial to listen to your vet’s guidance and closely adhere to their instructions. This way, you can ensure your dog receives the best care and treatment for their infection.

Uses: Antibiotics For Dogs

Antibiotics for dogs are prescribed to treat a wide range of bacterial infections. Dogs can be susceptible to various disease-causing bacteria, and some of the most common are:

• Bordetella bronchiseptica: This bacterium is the primary cause of kennel cough, a highly contagious respiratory disease in dogs.¹¹
• Leptospira spp.: Leptospirosis targets the red blood cells of dogs, causing them to clot abnormally. This species of bacteria can be found in bodies of water that contain the urine of infected animals and enters the body through skin wounds and mucous membranes.
• Campylobacter spp.: Campylobacter spp. is one of the most common causes of gastroenteritis in dogs, which is an inflammation of the stomach and intestines.¹²
• Salmonella spp.: Salmonella bacteria can be found on contaminated food and infected feces, causing fevers and worrying gastrointestinal issues in dogs.¹³
• Clostridium spp.: While Clostridium bacteria are typically present in the environment and can naturally reside in your dog's gastrointestinal tract, there are instances where they can produce toxins, resulting in the development of severe illnesses.¹⁴
• Staphylococcus spp.: These bacteria are part of your dog’s normal skin flora but can cause skin infections if they penetrate the skin's barrier, which often occurs due to cuts, wounds, or bites.¹⁵

Now that we have covered the bacteria most commonly associated with illnesses in dogs, let's shift our focus to the broader application of antibiotics for dogs. Dog antibiotics can be used to treat:

• Skin and soft tissue infections: Often secondary to other conditions like allergies or injuries, skin infections often require antibiotic treatment.
• UTIs: When bacteria multiply in your dog's urinary tract, it is often necessary to administer antibiotics for treatment.
• Respiratory infections: Bacterial infections in the lungs, windpipe, or nasal passages can also be treated with antibiotics.
• Gastrointestinal infections: Although gastrointestinal infections can be caused by viruses, parasites, or dietary issues as well, bacterial infections are treated with antibiotics.
• Ear and eye infections: Ear infections that come with ear mites and allergies can be treated with antibiotic ear drops. Eye infections caused by foreign bodies entering your dog’s eyes typically require the use of antibiotic eye drops.
• Bone and joint infections: Bone and joint infections tend to be very serious and require antibiotic treatment.
• Dental infections: Gum disease is a common issue in dogs and, if left untreated, can result in tooth loss. Administering antibiotics can aid in the healing of your dog's gums.
• Post-surgical prophylaxis: After a surgical procedure, antibiotics are often administered to prevent potential bacterial infections.

What Are The Side Effects Of Antibiotics For Dogs?

Like any medication, antibiotics for dogs come with potential side effects. These side effects can range from mild to severe, depending on the specific antibiotic used, the dosage, the duration of treatment, and your dog's health condition and reaction to the medication.

Some of the most common side effects include:

• Gastrointestinal issues: Loss of appetite, vomiting, diarrhea, or other changes in bowel movements.
• Allergic reactions: Itching, rashes, difficulty breathing, or in severe cases, anaphylaxis, which is a medical emergency that requires immediate veterinary attention.
• Behavioral changes: Restlessness, lethargy, or fatigue.

Rare side effects include:

• Tremors
• Muscle spasms
• Seizures
• Photosensitivity
• Yeast infections
• Irregular heartbeat
• Organ damage

Make sure to closely monitor your dog after giving them antibiotics. If you notice any concerning signs or symptoms, don't hesitate to reach out to a vet for assistance.

Antibiotic Safety

While antibiotics are generally very safe for dogs when prescribed by a vet, it is still crucial to follow a few best practices to maximize their effectiveness and ensure the well-being of your beloved pup.

• Follow your vet’s instructions: Always give your dog the prescribed dosage at the correct times.
• Give with food if directed: Some antibiotics can cause stomach upset if taken without food. Others, on the other hand, are meant to be taken on an empty stomach.
• Don’t mix with other medications without approval: Some antibiotics can interact with other drugs, so don't give your dog any other medications, supplements, or even certain foods without first checking with your vet.
• Closely monitor your dog: Keep a close eye on your dog while they're taking antibiotics. Watch for any side effects or changes in behavior, appetite, or bowel movements. If you notice anything concerning, call your vet immediately.
• Store the antibiotics properly: Keep your dog’s antibiotics in a cool, dry place out of reach of pets and children. Some liquid antibiotics need to be refrigerated. Always check the bottle for storage instructions.
• Complete the full course of antibiotics: Even if your dog seems to be feeling better, always finish administering the antibiotics prescribed to them. Discontinuing antibiotics early can lead to a resurgence of the infection and contribute to antibiotic resistance.

FAQs

Can I get antibiotics for my dog without seeing a vet?

No, it's generally not legal or safe to get antibiotics for your dog without seeing a vet. Antibiotics should only be used under the supervision of a veterinarian. Misuse of antibiotics can lead to antibiotic resistance and can harm your pet.

Are there over-the-counter antibiotics for dogs?

No, there are no over-the-counter antibiotics for dogs. Antibiotics are prescription medications, and a veterinarian should examine your dog and make an appropriate prescription based on the type and severity of the infection.

Is veterinary amoxicillin the same as human amoxicillin?

No, veterinary amoxicillin is generally not the same as human amoxicillin. They tend to differ in formulation. Veterinary amoxicillin clavulanic acid, for example, contains a different ratio of ingredients when compared to the same product for humans.

Which antibiotic is best for dogs?

The "best" antibiotic for a dog depends on the type of infection, the dog's overall health, weight, allergies, pre-existing health conditions, and more. A vet will determine the best prescription for your dog after a thorough examination and understanding of their medical history.

Final Notes

All in all, antibiotics play a critical role in managing various bacterial infections in dogs, ensuring their health and well-being. However, they must be used responsibly and strictly under the guidance of a veterinarian. The misuse of these medications can not only lead to serious side effects but also contribute to antibiotic resistance.

If you have any other questions about antibiotics for dogs, speak with a Dutch vet. With a Dutch subscription, you can get your dog’s condition diagnosed from the comfort of your home, have prescriptions delivered straight to your door from our online pharmacy, and benefit from unlimited vet visits and follow-ups. Created by pet parents for pet parents, Dutch provides easy, affordable online vet care for a range of pet health issues, including anxiety, arthritis, urinary issues, and more. Try Dutch today.