Veterinarians use doxycycline, an antibiotic in the tetracycline family, for dogs with infections caused by bacteria and by microorganisms that are unresponsive to common antibiotics. It is not approved for use in animals by the Food and Drug Administration but vets prescribe it legally as an "extra-label drug."
Doxycycline does not kill bacteria; it inhibits their ability to reproduce. Doxycycline is not effective for treating viral and fungal infections in dogs.
As always, tell your vet about any medications your dog is taking and about any other health issues.
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Uses of Doxycycline for Dogs
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If your dog seems lethargic or has respiratory symptoms, contact your veterinarian. Doxycycline is a prescription antibiotic that treats dogs' respiratory infections caused by bacteria. If you notice symptoms of respiratory distress, including coughing, wheezing, difficulty breathing, fever, lethargy and nasal discharge, take your dog to the veterinarian as soon as possible.
Other bacterial infections treated with doxycycline are mycoplasma bacteria and kennel cough, urinary tract infections, blood-borne infections and wound infections. It is especially effective for treating tick-borne bacterial diseases such as Rocky Mountain spotted fever and ehrlichiosis, and water-borne infections such as leptospirosis.
Potential Side Effects of Doxycycline
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Doxycycline may cause mild side effects in dogs, most commonly nausea and vomiting, but you can prevent these by giving doxycycline with food or shortly after feeding. Contact your veterinarian immediately if your dog continues vomiting or exhibits other side effects, such as a skin rash, diarrhea or appetite loss. Some dogs may be allergic to doxycycline, so let your vet know if your dog has reacted to medications in the past.
For doxycycline to work properly, your dog's immune system must be active and effective, so this may not be the best medication choice for immune compromised dogs.
Interactions with other Drugs
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Doxycycline may interact with other medications, such as laxatives, calcium supplements, antacids, iron supplements, kaolin (found in Kaopectate), bismuth subsalicylate (the main ingredient in Pepto Bismol), and certain antibiotics or vitamins, so do not give your dog any drug or supplement without first consulting your vet.
Doxycycline Dosage
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Always follow your veterinarian's directions and the label instructions, and, to avoid an overdose, give your dog the correct amount of doxycycline. Unless specifically instructed by your veterinarian, always give your dog the entire prescription to prevent relapse or drug resistance, even if your pet feels better and the symptoms have subsided.
Doxycycline is available as tablets, capsules, oral liquid suspension and as an injectable solution.
How Doxycycline Works
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"The tetracycline antibiotic family provides broad antibacterial protection by inhibiting bacterial protein synthesis," says Wendy C. Brooks, DVM, the educational director of Veterinary Partner. "The body possesses many barriers through which antibiotics have difficulty penetrating and infections behind these barriers can be difficult to treat," but doxycycline is able to penetrate certain biological barriers, making it especially helpful in treating intracellular infections.
Doxycycline and Heartworm Disease
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Combining ivermectin and doxycycline for heartworm treatment may be dangerous for collies. In August 2006, the Whole Dog Journal reported on the finding that, "heartworms harbor a symbiotic organism called Wolbachia, and that treatment with doxycycline to destroy the Wolbachia could reduce the chance of adverse reactions during heartworm treatment."
The August 2009 Whole Dog Journal updated study results with information that "treatment with a combination of weekly ivermectin (Heartgard) and intermittent doxycycline helps rid the dog's body of adult worms, reduces the effects of the worms, stops worms' egg production, and renders the heartworms noninfectious to other dogs." In addition, mosquitoes that fed on dogs treated with doxycycline produced heartworm larvae that did not infect other dogs.
Weekly doses of Heartgard may be safe for many dogs, but collies and related breeds that test positive for the mutant MDR1 gene are very sensitive to ivermectin and a number of other drugs, and should never be given these drugs as they could cause neurotoxicity.
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