An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting bacterial infections, and antibiotic medications are widely used in the treatment and prevention of such infections. They may either kill or inhibit the growth of bacteria.

The word antibiotic means “against life.” Any drug that kills germs in your body is technically an antibiotic. But most people use the term when they’re talking about medicine that is meant to kill bacteria.

Antibiotics play a crucial role in veterinary medicine, helping to treat bacterial infections and improve the health of our furry friends. However, like any medication, antibiotics can have side effects that pet owners should be aware of.

Only bacterial infections can be killed with antibiotics. The common cold, flu, coughs, bronchitis infections, sore throats, and stomach flu are all caused by viruses. Antibiotics won’t work to treat them. Your doctor will tell you either to wait for these illnesses out or prescribe antiviral drugs to help you get rid of them.

Just like medicines that we humans take, antibiotics can have side effects. Usually, these side effects are mild, but if your pet is showing any abnormal signs while they are on antibiotics, you should consult your vet. 

In some cases, antibiotics can also disrupt the normal balance of microorganisms in a dog’s body, leading to secondary infections such as yeast infections. These infections can manifest as itching, redness, or discharge in areas such as the ears, paws, or skin folds. 

In this blog post, we will tell you more about antibiotics and their effect on dogs. Remember it’s highly important that the antibiotics for dogs have been prescribed by your vet.

Also, It’s worth noting that not all dogs will experience side effects from antibiotics, and many can tolerate them without any issues, but keep reading for more juicy information.

What Are Antibiotics & How Do They Work?

The introduction of antibiotics into medicine revolutionised the way infectious diseases were treated. Between 1945 and 1972, average human life expectancy jumped by eight years, with antibiotics used to treat infections that were previously likely to kill patients. 

Today, antibiotics are one of the most common classes of drugs used in medicine and make possible many of the complex surgeries that have become routine around the world.

When your dog is not feeling well, you feel bothered as a dog parent, seeking solutions on how to make them feel well as fast as possible and even painlessly. This might mean giving them antibiotics that will help kill bacteria.

There are two main ways in which antibiotics target bacteria. They either prevent the reproduction of bacteria or kill the bacteria, for example by stopping the mechanism responsible for building their cell walls.

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.

If your veterinarian determines that an antibiotic would be effective, the next step is to determine what pet antibiotic is most effective, since most antibiotics don’t treat specific conditions, but rather types of bacteria. 

Accurate diagnosis is essential. 

This allows for proper treatment and the correct choice of antibiotic. Veterinary practitioners are best placed to make this decision. According to the Merck Veterinary Manual, successful antibiotic treatment is based on four key steps.

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.

1. Penicillins: 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. 

Penicillin is most often administered via injection, but it’s also available as a tablet, liquid, or gel. Penicillin tablets are best given on an empty stomach. If vomiting or nausea occurs, give penicillin with food. 

The dosage amount will vary based on the type of penicillin, as well as your dog’s age and condition. Always follow your vet’s dosage instructions. Never discontinue a course of antibiotics before it runs out unless your vet explicitly instructs you to do so.

2. Cephalosporins: Cephalosporin, the main ingredient in Cephalexin, treats bacterial infections of the skin, bones, joints, bladder, pneumonia and respiratory tract in dogs and cats. The medication is used as a low-dose antibiotic and may be administered over an extended time period.

3. Cephamycins: Cephalosporins include cephamycins, which differ from other cephalosporins in that they contain a 7-alpha-methoxy group, which imparts resistance to extended-spectrum beta-lactamases. 

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. 

The physical and chemical properties of the cephalosporins are similar to those of the penicillins, although the cephalosporins are somewhat more stable to pH and temperature changes. 

Cephalosporins are weak acids derived from 7-aminocephalosporanic acid. They are used either as the free base form for PO administration (if acid-stable) or as sodium salts in an aqueous solution for parenteral delivery (sodium salt of cephalothin contains 2.4 mEq of sodium/g). 

4. Aminoglycosides: Aminoglycoside is a medicinal and bacteriologic category of traditional Gram-negative antibacterial medications that inhibit protein synthesis and contain as a portion of the molecule an amino-modified glycoside. The term can also refer more generally to any organic molecule that contains amino sugar substructures. 

5. 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.

6. Macrolides: Macrolide antibiotics are used for dogs, Macrolides are a class of drugs used to manage and treat various bacterial infections. Azithromycin, clarithromycin, and erythromycin are commonly used to treat infections like pneumonia, sinusitis, pharyngitis, and tonsillitis. 

7. Tetracyclines: Tetracycline is a broad-spectrum antibiotic from the same family as oxytetracycline, doxycycline, minocycline, and others. The tetracycline antibiotics are bacteriostatic. 

Their mechanism of action is through the reversible binding of bacterial 30S ribosomes and the alteration of the bacterial cytoplasmic membrane. Tetracycline antibiotics are used to treat bacterial infections due to aerobic, gram-positive and gram-negative bacteria, mycoplasma, rickettsiae, chlamydia, and some protozoa.

8. 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.

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5 Common Antibiotics for Dogs/Side Effects Of Antibiotics In Dogs

1. Penicillin

Penicillins are a group of β-lactam antibiotics originally obtained from Penicillium moulds, principally P. chrysogenum and P. rubens. Most penicillins in clinical use are synthesised by P. chrysogenum using deep tank fermentation and then purified.

According to the American Chemical Society, penicillin was discovered by Alexander Fleming on September 3, 1928. It was the first antibiotic and became a life-saving drug for treating infections in people. 

Penicillins damage the cell wall of bacteria and can also interfere with enzymes important to cell wall synthesis. Several antibiotics for dogs are in the penicillin class:

• Amoxicillin
• Amoxicillin-clavulanate (Clavamox)
• Penicillin G
• Ampicillin
• Ampicillin-sulbactam (Unasyn)

Effectiveness

Penicillins were among the first medications to be effective against many bacterial infections caused by staphylococci and streptococci. They are still widely used today for different bacterial infections, though many types of bacteria have developed resistance following extensive use.

Penicillin can be used to treat urinary tract infections, skin infections or wounds, and upper respiratory infections, or as part of a combination protocols for liver and biliary disease, serious systemic infections, or sepsis in dogs. 

In many infections, penicillins may be one of the first antibiotics used for treatment before further testing is done or a culture is taken.

Cautions

Dogs can take penicillin. The more serious side effects of penicillin are rare but they are possible. Your dog could experience irregular breathing patterns, fever, rash, or swelling around its face. 

If you notice any of these symptoms please reach out to your veterinarian right away so that your dog can be treated

2. Fluoroquinolones For Dogs

Fluoroquinolone antibacterial agents are among the most important antimicrobials used in veterinary medicine. They are used in practically all species and have a broad spectrum of activity that includes most of the important veterinary bacterial pathogens. 

Since their first introduction in the late 1980s (discussed in previous editions of this book), the use of fluoroquinolones has expanded tremendously.

They are bactericidal antibiotics that inhibit bacterial growth by targeting enzymes vital to DNA replication. 

Fluoroquinolones are available in oral and injectable forms, and different types are available specifically for dogs compared to those used in people. Common fluoroquinolone antibiotics used in dogs include:

• Enrofloxacin (Baytril)
• Orbifloxacin (Orbax)
• Marbofloxacin (Zeniquin)
• Ciprofloxacin

Effectiveness

Most veterinary fluoroquinolones (enrofloxacin, marbofloxacin, orbifloxacin) have activity primarily against gram-negative bacteria by acting on DNA gyrase, inhibiting supercoiling of DNA. 

Fluoroquinolones are used to treat many gram-negative bacterial infections, including those with Escherichia coli, Klebsiella, or Pseudomonas. Infections of the respiratory tract, intestines, urinary tract, and skin are often susceptible. 

pradofloxacin appeared to be a safe and effective treatment for deep pyoderma in dogs. In general, this class of drug is not effective against Staphylococcus spp., Streptococcus spp., Brucella spp., Mycoplasma spp., Mycobacteria spp., or anaerobic bacteria. 

Cautions

Difloxacin may cause some nausea, vomiting, and diarrhea at high doses. All of the fluoroquinolones may cause arthropathy in young animals.When using a fluoroquinolone antibiotic, making adjustments to the dosages of other drugs being administered is sometimes necessary.

These antibiotics can disrupt the normal flora of the gastrointestinal tract and their use in treating canines may lead to vomiting, diarrhoea, or poor appetite. 

Other side effects of fluoroquinolones include damage to the joints of growing dogs when used at high doses, allergic reactions, and rarely, elevated liver enzymes, nervousness, and neurologic symptoms. 

3. Tetracyclines For Dogs

Tetracycline is a broad spectrum antibiotic that is used to treat a wide variety of infections caused by bacteria and other types of organisms.

Tetracycline also has some calming effects on the immune system and may be used with corticosteroids and niacinamide to treat an autoimmune disease called cutaneous discoid lupus erythematosus in dogs. 

After usual oral dosage, tetracyclines are absorbed primarily in the upper small intestine, and effective blood concentrations are reached in 2–4 hours. Gastrointestinal absorption can be impaired by sodium bicarbonate, aluminum hydroxide, magnesium hydroxide, iron, calcium salts, and (except for the lipid-soluble tetracyclines doxycycline and minocycline) milk and milk products.

Effectiveness

Tetracyclines are more effective against multiplying microorganisms and tend to be more active at a pH of 6–6.5. 

Veterinary experts agree that doxycycline is the antibiotic of choice for use in dogs with tick-borne diseases, such as Lyme disease, ehrlichiosis, or anaplasmosis. 

It can also be used to treat respiratory infections, such as kennel cough. It is also effective against leptospirosis, Bartonella spp., and some staph infections. Minocycline is another tetracycline antibiotic that is used on occasion.

Cautions

Potential side effects of doxycycline in dogs include vomiting, diarrhoea, loss of appetite, the elevation of liver enzymes, and allergic reactions. 

Tetracycline should not be used in animals with known hypersensitivity or allergy to the drug. 

This antibiotic is not recommended for use during a dog’s pregnancy, as congenital defects or dental or bone staining can result.

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4. Cephalosporins For Dogs

Cephalosporin antibiotic. Action is similar to other beta-lactam antibiotics, which inhibit the synthesis of the bacterial cell wall, leading to cell death. Cephalosporins are divided into first-, second-, third-, and fourth-generation drugs depending on the spectrum of activity

Cefpodoxime (PO) has been approved for use in dogs, and cefovecin (SC) has been approved for use in dogs and cats. Cephalosporins are particularly useful to treat infections of soft tissue and bone due to bacteria that are resistant to other commonly used antimicrobials.

Cephalosporins are bactericidal and work in a similar fashion to penicillins by attacking bacterial cell walls. Some cephalosporins available for dogs include:

• Cephalexin (Keflex, Rilexine)
• Cefadroxil (Cefa-Tabs, Cefa-Drops)
• Cefazolin – a common injectable cephalosporin
• Ceftiofur (Naxcel)
• Cefpodoxime (Simplicef)
• Cefovicin (Convenia), a long-acting injectable antibiotic for dogs and cats

Effectiveness

First-generation cephalosporins are useful in treating gram-positive bacterial infections and a few gram-negative bacterial infections, including those with E. coli, Proteus, Klebsiella, Salmonella, and Enterobacter. 

Cephalexin and cefpodoxime are most often used to treat skin infections (Staphylococcus pseudintermedius) and urinary tract infections but are not as useful against anaerobic bacteria as are penicillins.

Second- and third-generation cephalosporins have a broader spectrum of activity with less bacterial resistance. These can be used during surgery and are effective against a variety of gram-positive and gram-negative organisms, depending on the specific drug.

Cautions

As with other antibiotic classes, these medications can potentially lead to gastrointestinal upset, including vomiting, diarrhoea, or poor appetite. 

Other side effects of cephalosporins include allergic reaction, increased salivation, hyperexcitability, and with high doses, or rarely, kidney toxicity, severe skin reactions, neurologic symptoms, or blood cell changes. It’s important to speak to your veterinarian right away if you notice any adverse effects.

5. Nitroimidazoles For Dogs

The 5-nitroimidazoles are a group of drugs that have both antiprotozoal and antibacterial activity. Nitroimidazoles with activity against trichomonads and amebae include metronidazole, tinidazole, nimorazole, flunidazole, and ronidazole. 

Metronidazole and nimorazole are effective in treatment of giardiasis, whereas dimetridazole, ipronidazole, and ronidazole control histomoniasis in poultry. Several nitroimidazoles have activity against trypanosomes.

Effectiveness

Metronidazole is used to treat anaerobic bacteria infections and certain protozoal parasite infections, such as Giardia. Susceptible bacteria may include Bacteroides fragilis, Fusobacterium spp., and Clostridium spp. 

Metronidazole is also used for the treatment of inflammatory bowel disease, oral and dental infections, pancreatic insufficiency, or other infections causing diarrhoea.

Cautions

Adverse effects are not commonly associated with metronidazole. High doses may induce clinical signs of neurotoxicity in dogs, such as tremors, muscle spasms, ataxia, and even convulsions. 

After IV dosing, CNS excitement has been observed. Reversible bone marrow depression has been reported.

When metronidazole is used at moderate to high doses over a long period, your dog may develop neurologic symptoms, including ataxia (wobbliness), difficulty walking, or abnormal eye movements. 

Fortunately, these symptoms will stop once the medication is out of your dog’s system. Metronidazole is not recommended for use in pregnant dogs.

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:  Only a veterinarian can diagnose and prescribe antibiotics for your dog. They will determine if antibiotics are necessary and select the most appropriate medication. 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: avoid mixing your dog’s antibiotics without the veterinarian’s approval, it’s very risky to do such.  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 an eye on your dog while they are on antibiotics.  Watch for any side effects or changes in behavior, appetite, or bowel movements. If you notice any unusual or concerning symptoms, contact your veterinarian.
• Store the antibiotics properly: Remember, antibiotics are a valuable tool in veterinary medicine, but they should be used judiciously and under professional guidance.  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.

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Why Do Dogs Need Antibiotics?

Like humans, dogs and cats develop bacterial infections that require a treatment program involving antibiotics. 

Antibacterial medications are essential for treating these infections because they destroy the infected organism while leaving your pet’s healthy cells intact. Here are some common reasons why dogs may need antibiotics:

1. Skin Infections: Skin problems in dogs are more common during the warmer seasons, which is when seasonal allergies (such as those to pollen and plants), insect bites and other allergic symptoms are more likely. It’s important to pay attention to any skin conditions your dog suffers from, even if they appear relatively minor. 

Skin symptoms in dogs – such as itching, rashes or bald patches, could be an indicator of an underlying cause or health condition that hasn’t already been diagnosed by a vet or vet nurse. 

2. Urinary Tract Infections (UTIs): Urinary tract infections (UTIs) are fairly common in dogs. Dogs with UTIs generally attempt to urinate very frequently whenever they go outside. They also may strain to urinate, or cry out or whine when urinating if it is painful. Sometimes you might even see blood in their urine.

Dripping urine, or frequent licking of the genitals, may also signal that a UTI is present. Urine that has a very strong odour to it can also be a sign that your dog has an infection. Antibiotics are prescribed to target the specific bacteria causing the infection and clear it up.

3. Respiratory Infections: Dogs can contract respiratory infections, such as bronchitis or pneumonia, which are often caused by bacteria. Dogs show a number of symptoms when they have a respiratory infection, including watery eyes, discharge from the nose, sneezing, coughing, difficulty breathing, and fever. 

Your dog may not want to play as usual or may refuse to eat. Antibiotics help combat bacterial infection, reduce inflammation, and promote healing of the respiratory system.

4. Dental Infections: Dog tooth infections are a medical emergency because they’re painful and can lead to illness. Common causes of tooth abscesses in dogs are trauma, broken teeth, and periodontal disease. 

You can help prevent this painful condition by properly caring for your dog’s oral health and never letting them chew on hard materials. Antibiotics may be prescribed to control the infection before dental procedures or to treat existing infections.

5. Ear Infections: Ear infections are common conditions in dogs, especially those with floppy ears such as Basset Hounds and Cocker Spaniels. An estimated 20 per cent of dogs have some form of ear disease, which may affect one or both ears. 

Fortunately, there are steps you can take to reduce the length and severity of these episodes for your dog and antibiotics are often part of the treatment plan to clear the infection and alleviate symptoms.

6. Bite Wounds: Dogs may get into fights or suffer from animal bites, leading to puncture wounds that can become infected. Antibiotics can prevent or treat infection in these cases, reducing the risk of complications.

7. Post-Surgical Infections: After surgical procedures, dogs are susceptible to bacterial infections at the incision site. Antibiotics may be prescribed to prevent infection or to treat existing infections to promote healing.

8. Gastrointestinal Infections: Dogs can experience bacterial infections in their digestive system, leading to symptoms like diarrhoea, vomiting, and abdominal pain. Antibiotics may be used to target the specific bacteria causing the infection and restore normal gut function.

Dog Lovers’ Opinion About The Side Effects Of Antibiotics In Dogs?

Generally, antibiotics are commonly used to treat bacterial infections in dogs. However, they can be effective in fighting infections, they may also have some side effects. The specific side effects can vary depending on the type of antibiotic used and the individual dog. Some potential side effects of antibiotics in dogs may include:

1. Gastrointestinal Upset: Antibiotics can disrupt the natural balance of bacteria in the gut, leading to symptoms such as diarrhea, vomiting, and loss of appetite. This is a common side effect and typically resolves once the antibiotic treatment is completed.
2. Allergic Reactions: Dogs may occasionally have allergic reactions to antibiotics, manifesting as skin rashes, itching, facial swelling, or difficulty breathing. If you notice any signs of an allergic reaction, it’s important to contact your veterinarian immediately.
3. Secondary Infections: In some cases, the use of antibiotics can disrupt the balance of bacteria in the body, leading to an overgrowth of certain bacteria or fungi. This can result in secondary infections, such as yeast infections or bacterial overgrowth in the gut.
4. Resistant Bacterial Infections: Overuse or misuse of antibiotics can contribute to the development of antibiotic-resistant bacteria, which can be more difficult to treat in the future. It’s important to follow your veterinarian’s instructions regarding the proper dosage and duration of antibiotic treatment.

Dog lovers who want the best out of their furry pals should note that while antibiotics can be necessary and beneficial in treating certain infections, they should always be used under the guidance of a veterinarian.

Your veterinarian will consider the specific infection, the overall health of your dog, and the potential risks and benefits of antibiotic treatment.

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Conclusion 

In conclusion, antibiotics play a crucial role in treating bacterial infections in dogs. When prescribed and used correctly, they can effectively eliminate harmful bacteria and promote the dog’s recovery. 

However, responsible use of antibiotics is essential to minimize the risk of antibiotic resistance and potential side effects. It is important to always consult a veterinarian for proper diagnosis and prescription, follow the prescribed dosage and complete the full course of treatment. 

Monitoring for any adverse reactions and avoiding self-medication are also key. By working closely with veterinarians, we can ensure the appropriate use of antibiotics and safeguard the health of our furry companions.