My veterinarian prescribed doxycycline for my cat. What is this? How does it work and does it produce any side effects?
Doxycycline is a semi-synthetic antibiotic derived from oxytetracycline. As with all members of the tetracycline family, doxycycline is essentially bacteriostatic. This means that rather than killing susceptible bacteria and certain other microbes, it inhibits bacterial growth by interfering with protein synthesis and thus microbial reproduction. Doxycycline and other tetracyclines are effective against many species of microorganisms. These include Chlamydia species that cause specific ailments in cats and dogs, Haemobartonella, Bartonella, and the rickettsiae, one of whose members causes Rocky Mountain Spotted Fever.
Although bacteriostatic agents tend to work slightly slower than bactericidal drugs that actually kill bacteria, the time of response to treatment with doxycycline depends on the condition being treated. For example, if patients are acutely lame with fever due to a rickettsial infection, many patients are better in 48 to 72 hours after commencing treatment with doxycycline.
Doxycycline also has anti-inflammatory properties that are separate from its antibiotic or antimicrobial properties, so it is possible for a cat or dog treated with doxycycline for lameness to improve without a specific infection present.
Nausea and vomiting are the most common side effects of doxycycline in cats and dogs. Administering this drug with food helps prevent or improve these adverse effects. Diarrhea is not uncommon, but occurs less than with other tetracyclines. Since the tetracycline drugs can retard fetal development and discolor tooth enamel, doxycycline should be avoided in pregnant animals, nursing mothers, or puppies or kittens younger than six months of age, unless absolutely necessary. Doxycycline, unlike other tetracyclines, appears safe to use in animals with renal problems. Generally the drug is quite safe: reports of photosensitization, skin eruptions and liver toxicity are uncommon.
09/21/00
