DogSource: Greene 2006
General infection: 3–5 mg/kg · every 12 h · 7–14 days
Antibiotic Therapy
Doxycycline
Tetracycline · bacteriostatic, protein-synthesis inhibitor (30S ribosome)
Species: Dogs & Cats15 dose protocols9 dosage forms
This page is a calculation and educational reference for veterinarians and veterinary students. It does not replace examination, culture and susceptibility testing, clinical judgment, or the attending veterinarian's final decision.
Drug overview
Tetracycline · bacteriostatic, protein-synthesis inhibitor (30S ribosome)
Brand names: Vibramycin®
General dose: 5 mg/kg PO · every 12 h (or 10 mg/kg once daily)Source: Plumb's (general)
Spectrum of activity
A broad-spectrum, bacteriostatic tetracycline; its strength is intracellular/atypical bacteria and spirochetes — Rickettsia, Ehrlichia, Anaplasma, Mycoplasma, Chlamydia and spirochetes (Borrelia of Lyme disease, Leptospira, Treponema). It also covers part of the Gram-positives (Actinomyces, Nocardia, Listeria, Cutibacterium) and Gram-negatives (Pasteurella, Bordetella, Brucella, Haemophilus, Vibrio). It is active against Staphylococcus but strain-dependent and with rising resistance (best confirmed by culture); it is not reliable against streptococci. Resistance is common among Enterobacteriaceae (E. coli, Klebsiella), Bacteroides and Pseudomonas.
Veterinary uses and doses
General (susceptible) infections
DogSource: Greene 2006
Soft tissue / UTI: 4.4–11 mg/kg · every 12 h · 7–14 days
CatSource: Vaden 1995
General infection (cat): 5 mg/kg PO (or IV) · every 12 h
CatSource: Greene 2006
Systemic infection / bacteremia (cat): 5–11 mg/kg PO or IV · every 12 h
Ehrlichiosis / Anaplasmosis
DogSource: ACVIM / Merck
Canine ehrlichiosis/anaplasmosis (E. canis): 5 mg/kg every 12 h or 10 mg/kg every 24 h · 28 days
Clinical note: The standard course for canine monocytic ehrlichiosis (E. canis) is 28 days; shorter courses may transiently improve signs but relapse is common. Clinical improvement is usually seen within 24–48 hours.
DogSource: ACVIM / Greene
Severe/chronic cases (E. canis): 10 mg/kg · every 24 h · 28 days
Clinical note: Even in the chronic/severe (pancytopenic) phase the standard doxycycline course is still 28 days, and prolonging the antibiotic alone is not recommended. Hematologic abnormalities may take 3–6 months to normalize (this is not treatment failure). The prognosis of this phase is guarded and often needs supportive care (transfusion, and immunosuppression for the immune-mediated component); selected refractory cases are extended to about 6 weeks per clinical judgment.
CatSource: Greene 2006
Feline ehrlichiosis/anaplasmosis: 5–10 mg/kg · every 12 h · 21–28 days
Lyme disease
DogSource: ACVIM (Lyme)
Lyme disease: 10 mg/kg · every 12–24 h · 30 days
Clinical note: Doxycycline is first-line for Lyme disease; the ACVIM-recommended course is about 30 days.
Rocky Mountain spotted fever (Rickettsia)
DogSource: Breitschwerdt 2000
RMSF (Rickettsia rickettsii): 5 mg/kg · every 12 h
Leptospirosis (renal carrier clearance)
DogSource: ACVIM (Lepto)
Leptospira renal carrier: 5 mg/kg · every 12 h · 14 days (alternative: 10 mg/kg every 24 h)
Clinical note: Doxycycline is the drug of choice for leptospirosis and clears the renal carrier state. The ACVIM standard dose is 5 mg/kg every 12 h (or the equivalent 10 mg/kg every 24 h) for 14 days — avoid 10 mg/kg every 12 h (more than needed). If penicillin G (25,000–40,000 U/kg IV or IM every 12–24 h) was given instead during the acute leptospiremic phase, this 14-day doxycycline course should follow once the patient recovers.
Hemoplasmosis / hemotropic mycoplasmosis
CatSource: Lappin / Greene
Feline hemoplasmosis (M. haemofelis) / bartonellosis: 10 mg/kg · every 24 h (or 5 every 12 h) · 28 days
Clinical note: The recommended course is usually 2–4 weeks; treatment does not necessarily eradicate the infection and the cat may remain a carrier. For bartonellosis, azithromycin is a common alternative.
Toxoplasmosis
DogSource: Lappin 2000
Toxoplasma (dog): 5–10 mg/kg · every 12 h · 4 weeks
CatSource: Lappin 2000
Toxoplasma (cat): 5–10 mg/kg · every 12 h · 4 weeks
Salmon poisoning (Neorickettsia)
DogSource: Rikihisa 2005
Salmon poisoning: 10 mg/kg IV · every 12 h · at least 7 days
Anti-inflammatory (joint) effect
DogSource: Greene 2006
Anti-inflammatory joint effect: 3–4 mg/kg · once daily · 7–10 days
Dosage forms
- Capsule 100 mg
- Capsule 50 mg
- Capsule 20 mg
- Tablet 100 mg
- Tablet 50 mg
- Tablet 20 mg
- Suspension 25 mg/5 mL
- Syrup 50 mg/5 mL
- Injectable (diluted solution 10 mg/mL)
Safety and clinical notes
- ⚠️ In cats, never give a tablet or capsule “dry” — the risk of esophageal stricture is serious; follow with at least 6 mL of water or food, or use a liquid/paste form.
- If using a capsule, dissolve the required amount in about 5 mL of water as a solution or suspension and then give it (especially for fractional doses or cats).
- Use with caution in young and pregnant animals (possible tooth discoloration and effects on bone — although less than with other tetracyclines).
- Unlike other tetracyclines it can be used in renal impairment (mainly fecal excretion); but in severe hepatic disease (especially in cats) reduce the dose or avoid it.
- Oral absorption is reduced by calcium, magnesium, iron, zinc and aluminium cations, as well as antacids and dairy products; separate the timing of administration.
- Photosensitivity may occur.
- Oral or IV only; IM or SC injection is not recommended, and IV must be slow and diluted.
- The most common adverse effects are GI: nausea, vomiting, diarrhea and anorexia.
- There is no approved systemic veterinary product; use in dogs and cats is extra-label.
Cited sources
- Plumb's (general)
- Greene 2006
- Vaden 1995
- ACVIM / Merck
- ACVIM / Greene
- ACVIM (Lyme)
- Breitschwerdt 2000
- ACVIM (Lepto)
- Lappin / Greene
- Lappin 2000
- Rikihisa 2005
Calculate a weight-based dose
Drug-data last updated: