Azithromycin for Dogs – Long-Acting Macrolide
Azithromycin is a macrolide with excellent tissue penetration + anti-inflammatory + anti-protozoal activity.
Dose
5-10 mg/kg PO every 24 hours
Pulse dosing (q72h) possible after 5-day loading for some indications.
Dose Reference Table
| Weight | Range |
|---|---|
| 5 kg | 25-50 mg |
| 10 kg | 50-100 mg |
| 20 kg | 100-200 mg |
| 30 kg | 150-300 mg |
| 40 kg | 200-400 mg |
Tablets: 100, 200, 250, 500, 600 mg. Suspension: 100/200 mg per 5 mL.
Duration by Indication
| Indication | Duration |
|---|---|
| Kennel cough | 5-7 days |
| Respiratory | 5 days then q72h |
| Cryptosporidium | 5-7 days at 10-15 mg/kg |
| Bartonella | 21-42 days |
| Skin/soft tissue | 7-14 days |
Spectrum
- Gram-positive (Staph, Strep)
- Gram-negative (Bordetella, Pasteurella, Haemophilus)
- Atypical (Mycoplasma, Chlamydophila)
- Spirochetes (Borrelia)
- Bartonella
- Some protozoa (Cryptosporidium, Toxoplasma)
Advantages
- Long tissue half-life – pulse dosing possible
- Excellent tissue penetration
- Anti-inflammatory properties
- Less drug interactions than erythromycin
- Good palatability suspension
âš Cautions
- QT prolongation (rare) – caution with sotalol, dofetilide
- Antacids (Ca, Mg, Al) – separate by 2 hours
- Macrolide hypersensitivity
- Severe hepatic dysfunction
Side Effects
Common
- GI upset (vomiting, diarrhea)
- Anorexia
Rare
- QT prolongation
- Hepatic enzyme elevations
- Cholestatic hepatitis
- Allergic reactions
Frequently Asked Questions
How much azithromycin should I give my dog?
STANDARD DOSE: 5-10 mg/kg PO once daily. EXAMPLES: 1) 5 kg = 25-50 mg; 2) 10 kg = 50-100 mg; 3) 20 kg = 100-200 mg; 4) 30 kg = 150-300 mg; 5) 40 kg = 200-400 mg. TABLETS: 100, 200, 250, 500, 600 mg. SUSPENSION: 100 mg/5 mL or 200 mg/5 mL. DURATION: 1) Kennel cough 5-7 days; 2) Respiratory 5 days then pulse q72h; 3) Cryptosporidium 5-7 days at 10-15 mg/kg; 4) Bartonella 21-42 days; 5) Skin 7-14 days. ADMINISTRATION: tablets with or without food; suspension empty stomach preferred. SEPARATE from antacids (calcium, magnesium, aluminum) by 2 hours. Pulse dosing q72h possible after loading due to long tissue half-life.
What is azithromycin used for in dogs?
Multiple indications: 1) KENNEL COUGH (Bordetella bronchiseptica) – first-line; 5-10 mg/kg q24h x 5-7 days; often resolves in 3-5 days; 2) RESPIRATORY infections – Mycoplasma, Streptococcus, atypicals; 3) ATYPICAL bacteria (Mycoplasma, Chlamydophila); 4) CRYPTOSPORIDIUM – protozoal diarrhea; 5) BARTONELLA – vector-borne; long course 21-42 days; 6) SOFT TISSUE infections – mild; 7) ASPIRATION PNEUMONIA adjunct; 8) PROSTATIC infections (good penetration); 9) Some MRSP cases per culture sensitivity. ADVANTAGES: 1) ONCE-DAILY dosing; 2) Excellent tissue penetration; 3) Pulse dosing capability (long tissue half-life); 4) Anti-inflammatory effects; 5) Available oral suspension for small dogs; 6) Less drug interactions than erythromycin. Reserve for SPECIFIC indications (macrolide resistance development) – not first-line for routine infections like uncomplicated UTI (cephalexin better).
Is azithromycin safe for dogs? Side effects?
GENERALLY WELL-TOLERATED. SIDE EFFECTS: 1) GI UPSET (most common) – vomiting, diarrhea, anorexia; usually mild; give with food may help; 2) Mild hepatic enzyme elevations (rare); 3) QT PROLONGATION (rare cardiac); 4) Cholestatic hepatitis rare; 5) Allergic reactions rare; 6) C. difficile overgrowth potential. CONTRAINDICATIONS: 1) Macrolide hypersensitivity (allergic to erythromycin, clarithromycin); 2) Severe hepatic dysfunction; 3) QT prolongation (concurrent sotalol, dofetilide caution); 4) Pregnancy – safety not established (use if benefit > risk). DRUG INTERACTIONS: 1) Digoxin – increased levels; 2) Cyclosporine – increased levels; 3) Antacids (Ca, Mg, Al) – separate by 2 hours; 4) Theophylline mild; 5) Warfarin – mild interaction; 6) Less interaction than erythromycin. SAFE in MDR1 breeds. Excellent safety profile overall. Most dogs tolerate well even long courses (Bartonella treatment 6 weeks).
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References & Further Reading
The dosing ranges and safety information on this page are drawn from the following veterinary references. Always defer to your own veterinarian and the manufacturer’s label for your specific product.
- Plumb DC. Azithromycin.
- Boothe DM. Small Animal Clinical Pharmacology and Therapeutics.
- Sykes JE. Greene’s Infectious Diseases of the Dog and Cat.
- Hopper K et al. Macrolides in veterinary medicine.
- PuppaDogs. Kennel Cough Calculator, Bordetella Calculator. puppadogs.com.
