Doxycycline
Antibiotic
View Brand Names (1)Dose and dosage
For susceptible infections:
a) General use for infection: 3–5 mg/kg PO q12h for 7–14 days; For soft tissue, urinary tract: 4.4–11 mg/kg PO or IV q12h for 7–14 days;
For acute E. canis infection: 5 mg/kg PO q12h or 10 mg/kg PO q24h for 14–16 days;
For chronic E. canis infection: 10 mg/kg PO q24h for 30–42 days. (Greene et al. 2006)
b) For canine granulocytic anaplasmosis (Anaplasma phagocytotophilum): 5 mg/kg PO q12h for 14 days; most dogs show clinical improvement in 24–48 hours. (Carrade et al. 2009)
c) For Lyme disease: 10 mg/kg PO q24h for 21–28 days (Appel & Jacobson 1995)
d) For Ehrlichiosis (E. canis) in dogs with a positive test result and clinical signs consistent with the infection: 10 mg/kg PO (rarely IV) q12- 24h for 28 days. (Ford 2009b)
e) For leptospirosis: 5–10 mg/kg PO twice daily for 2 weeks. Management of underlying renal disease is a must. Regardless 10-30% of patients die. (Ford 2009a)
f) For Toxoplasma gondii: 5–10 mg/kg PO q12h for 4 weeks (Lappin 2000a)
g) For Rocky Mountain Spotted-Fever (Rickettsia rickettsii): 5 mg/kg PO q12h (Breitschwerdt 2000)
h) For idiopathic lymphoplasmacytic (chronic) rhinitis: Long term administration of antibiotics having immunomodulatory effects combined with nonsteroidal antiinflammatory agents can be helpful in some dogs.
Doxycycline 3–5 mg/kg PO q12h, or azithromycin 5 mg/kg PO q24h in combination with piroxicam 0.3 mg/kg PO q24h. (Kuehn 2010)
i) For uncomplicated infectious tracheobronchitis (B. bronchiseptica): 5-10 mg/kg PO once daily for a minimum of 2 weeks; treatment for up to 3 months should be considered, particularly when managing simultaneous infections in multiple dogs in the same environment. (Ford 2009a)
j) In combination with ivermectin as an adulticide for D. immitis: In this study doxycycline was administered at 10 mg/kg PO once daily for 30 days along with ivermectin/pyrantel pamoate with the ivermectin dose at 6–14 micrograms/kg PO once every 15 days for 6 months. 100% (total of 11 dogs) were negative for circulating microfilaria by day 90. 74% of dogs were negative for circulating antigens at day 300 (4-months post
ivermectin). (Grandi et al. 2010)
k) For salmon poisoning (Neorickettsia helmintheca): 10 mg/kg IV twice a day for at least 7 days (Rikihisa & Zimmerman 1995)
For its antiarthritic effect:
a) 3–4 mg/kg PO once daily for 7–10 days. (Greene et al. 2006)
Do not dry pill cats with oral doxycycline; follow with at least 6 mL of water or use a compounded slurry (“triple fish” or similar) to administer.
For susceptible infections:
a) For Hemotropic mycoplasmosis: 5–10 mg/kg PO once daily for 14 days; round dose to nearest whole tablet or capsule;
For Bartonellosis: 50 mg (total dose) PO q12h for 14–28 days;
For systemic infections, bacteremia: 5–11 mg/kg PO or IV q12h as long as necessary;
For Ehrlichiosis or Anaplasmosis: 5–10 mg/kg PO q12h for 21 days (Greene et al. 2006)
b) For clinical hemoplasmosis or bartonellosis: 10 mg/kg PO q12–24h (Lappin 2006)
c) For Toxoplasma gondii: 5–10 mg/kg PO q12h for 4 weeks (Lappin 2000b)
d) For susceptible mycobacterial, L-Forms, or mycoplasma infections: 5– 10 mg/kg PO q12h. (Bonenberger 2009)
e) For treatment of Nocardia (N. nova) infections: Combination therapy with: amoxicillin 20 mg/kg PO twice daily with clarithromycin 62.5–125 mg (total dose per cat) PO twice daily and/or doxycycline 5 mg/kg or higher PO twice daily. (Malik 2006)
f) For feline chlamydial infections (C. felis): 10 mg/kg PO once daily for a minimum of 3–4 weeks; additional topical ocular treatment may reduce ocular discomfort. (Gruffyd-Jones 2009)
Warning: Doxycycline intravenously in horses has been associated with
fatalities. Until further work is done demonstrating the safety of this drug,
it cannot be recommended for parenteral use in this species.
a) For Lyme disease: 10 mg/kg PO once to twice daily for up to 30 days
(Divers 1999)
b) For equine granulocytic ehrlichiosis (anaplasmosis; EGE) as an alternative to oxytetracycline: 10 mg/kg PO q12h for 10-14 days. (Lewis
et al. 2009)
c) For organisms with an MIC ≤ 0.25 micrograms/mL (including many susceptible Streptococcus spp, Staphylococcus spp, Pasteurella spp,
Rhodococcus equi, Actinobacillus equuli, and most ehrlichial organisms), a dose of 20 mg/kg PO q24h; preferably food should be withheld for at least 8 hours before and 2 hours after dosing. For bacteria with an MIC of 0.5–1 micrograms/mL, 20 mg/kg PO q12h is necessary to maintain adequate trough levels. Feeding should ideally be withheld as above, but may not be practically possible. One horse in the study developed a severe, acute colitis and the authors recommended that further clinical and safety studies be performed before using this regimen. (Davis et al. 2006)
Tetracyclines generally act as bacteriostatic antibiotics and inhibit protein synthesis by reversibly binding to 30S ribosomal subunits of susceptible organisms, thereby preventing binding to those ribosomes of aminoacyl transfer-RNA. Tetracyclines also are believed to reversibly bind to 50S ribosomes and, additionally, alter cytoplasmic membrane permeability in susceptible organisms. In high concentrations, tetracyclines can also inhibit protein synthesis by mammalian cells.
As a class, the tetracyclines have activity against most mycoplasma, spirochetes (including the Lyme disease organism), Chlamydia and Rickettsia. Against gram-positive bacteria, the tetracyclines have activity against some strains of staphylococcus and streptococci, but resistance by these organisms is increasing. Gram-positive bacteria that are usually covered by tetracyclines include: Actinomyces spp., Bacillus anthracis, Clostridium perfringens and tetani, Listeria monocytogenes and Nocardia. Among gram-negative bacteria that tetracyclines usually have in vitro and in vivo activity against, include Bordetella spp., Brucella, Bartonella, Haemophilus spp., Pasturella multocida, Shigella, and Yersinia pestis. Many or most strains of E. coli, Klebsiella, Bacteroides, Enterobacter, Proteus and Pseudomonas aeruginosa are resistant to the tetracyclines.
Doxycycline generally has very similar activity as other tetracyclines against susceptible organisms, but some strains of bacteria may be more susceptible to doxycycline or minocycline and additional in vitro testing may be required.
The following drug interactions have either been reported or are theoretical in
humans or animals receiving doxycycline and may be of significance in
veterinary patients:
ANTACIDS, ORAL: When orally administered, tetracyclines can chelate divalent or trivalent cations that can decrease the absorption of the tetracycline or the other drug if it contains these cations. Oral antacids, saline cathartics, or other GI products containing aluminum, calcium, magnesium, zinc, or bismuth cations are most commonly associated with this interaction. Doxycycline has a relatively low affinity for calcium ions, but it is recommended that all oral tetracyclines be given at least 1–2 hours before or after the cation-containing product.
BISMUTH SUBSALICYLATE, KAOLIN, PECTIN: May reduce absorption
IRON, ORAL: Oral iron products are associated with decreased tetracycline absorption, and administration of iron salts should preferably be given 3 hours before or 2 hours after the tetracycline dose.
PENICILLINS: Bacteriostatic drugs, like the tetracyclines, may interfere with bactericidal activity of the penicillins, cephalosporins, and aminoglycosides. There is a fair amount of controversy regarding the actual clinical significance of this interaction, however.
PHENOBARBITAL: May decrease doxycycline half-life and reduce levels
WARFARIN: Tetracyclines may depress plasma prothrombin activity and patients on anticoagulant (e.g., warfarin) therapy may need dosage