# Azithromycin: veterinary dose and monograph

> Azithromycin is a veterinary antibiotic. Azalide (macrolide) — a long tissue half-life and intracellular / phagocyte concentration allow extended dosing intervals. Indications include respiratory infections (Bordetella, atypical pneumonia); feline bartonellosis and Chlamydophila; foal Rhodococcus equi pneumonia (with rifampin). This monograph lists 6 reference doses for dogs, cats, horses, birds, rabbits and guinea pigs, each with route, frequency and source.

Source: https://vetmasterji.com/drugs/azithromycin · Last reviewed: 2026-10-01

## At a glance

- **Drug class:** Antibiotic
- **Also known as:** Zithromax, Azee, Azithral
- **Species with doses:** Dogs, Cats, Horses, Birds, Rabbits and Guinea pigs
- **General dose range:** 5–10 mg/kg PO q24h then q48–72h — check the species tables for the indication
- **Routes:** PO
- **Last reviewed:** 1 October 2026

## Indications

- Respiratory infections (Bordetella, atypical pneumonia)
- Feline bartonellosis and Chlamydophila
- Foal Rhodococcus equi pneumonia (with rifampin)
- Avian chlamydiosis

## Azithromycin dose by species

Doses are per administration unless stated. mg/kg doses scale with body weight; per-animal, per-quarter and infusion-rate doses are shown as the reference writes them.

### Dogs

*Azithromycin doses for dogs*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Respiratory / soft-tissue infection | 5–10 mg/kg | PO | q24h × 2–5 d then q48–72h | — |

- Respiratory / soft-tissue infection: Plumb’s p.138: 5–10 mg/kg PO once daily for 3–5 days (Trepanier; Sykes); pyoderma 10 mg/kg once daily for 5–10 days; Babesia gibsoni 10 mg/kg once daily with atovaquone 13.3 mg/kg q8h for 10 days. Papich 5e: 10 mg/kg once daily for 5–7 days, then every other day; or 5 mg/kg/day.

### Cats

*Azithromycin doses for cats*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Bartonella / Chlamydophila / URI | 5–10 mg/kg | PO | q24h × 3 d then q72h | — |

- Bartonella / Chlamydophila / URI: Plumb’s p.138: 5–10 mg/kg PO once daily for 3–5 days; URI 5–10 mg/kg once daily for 5 days then every 3rd day for 6–8 weeks (Scherk 2006); Bartonella 10 mg/kg once daily for 21 days. Papich 5e: 5–10 mg/kg once daily for 7 days then q48h; URI 15 mg/kg daily for 3 days then q72h.

### Horses

*Azithromycin doses for horses*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Foal R. equi pneumonia | 10 mg/kg | PO | q24h for 5 days, then q48h | — |

- Foal R. equi pneumonia: Papich 5e and Plumb’s p.138 (Jacks 2001): 10 mg/kg PO once daily for 5 days, then every other day once responding. Usually combined with rifampin. Adult horses (Papich): 10 mg/kg PO q48h — watch for colitis in adults.

### Birds

*Azithromycin doses for birds*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Chlamydiosis | 40 mg/kg | PO | q48h | 21 days |

- Chlamydiosis: Plumb’s p.138 (Guzman 2010): experimentally infected cockatiels — 40 mg/kg PO every other day for 21 days, as effective as 21 or 45 days of doxycycline; dosed by crop tube with the human oral suspension.

### Rabbits

*Azithromycin doses for rabbits*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Jaw abscess / osteomyelitis | 15–30 mg/kg | PO | q24h | 2–4 weeks post-op |

- Jaw abscess / osteomyelitis: Plumb’s p.138: jaw abscesses 15–30 mg/kg PO once daily for 2–4 weeks after surgery (Johnson 2006); Staphylococcus osteomyelitis 50 mg/kg PO once daily with rifampin 40 mg/kg q12h (Ivey & Morrisey 2000). Stop if anorexia or diarrhoea develops.

### Guinea pigs

*Azithromycin doses for guinea pigs*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Pneumonia | 15–30 mg/kg | PO | q24h | — |

- Pneumonia: Plumb’s p.138 (Johnson 2006): guinea pigs 15–30 mg/kg PO once daily. Stop if soft stools develop.

## Contraindications

Macrolide hypersensitivity. Hepatic impairment (hepatic metabolism). Caution with QT-prolonging drugs. Adult horses — risk of severe diarrhoea (reserve for foals).

## Species-specific warnings

> **Caution:** Horses: Use only in foals — adult horses develop life-threatening colitis. Hyperthermia / anhidrosis is reported in treated foals during hot weather.

## Adverse effects

- GI upset — vomiting, diarrhoea
- Hepatic enzyme elevation
- Foal hyperthermia / diarrhoea

## Drug interactions

- Oral antacids (magnesium- and aluminium-containing): reduce the RATE of azithromycin absorption — separate doses by 2 hours
- Cisapride: no azithromycin-specific data, but other macrolides are contraindicated with cisapride — use with caution
- Cyclosporine: azithromycin may raise cyclosporine blood levels — monitor closely
- Digoxin: no azithromycin-specific data, but other macrolides raise digoxin levels — monitor
- Pimozide: CONTRAINDICATED — acute deaths have occurred (human drug, unlikely in veterinary practice)

## Toxicity and overdose

Plumb's: acute oral overdose is unlikely to cause significant morbidity beyond vomiting, diarrhoea and GI cramping. As with all macrolides, the serious species risk is not overdose but the class effect — macrolides can precipitate fatal enterocolitis/enterotoxaemia in rabbits and other hindgut fermenters, and are contraindicated by the oral route in adult horses (Clostridium difficile colitis).

## Clinical pearls

- Long tissue half-life means short courses with extended intervals — improves compliance
- For foal R. equi, combine with rifampin and watch the mare for antibiotic-associated colitis from coprophagia
- Keep dairy / food-animal use off-label and avoid — prolonged residues

## Mechanism of action

Azithromycin is an azalide (macrolide subclass). Plumb's: penetrates the cell wall and binds the 50S ribosomal subunit, inhibiting bacterial protein synthesis — bacteriostatic. Relatively broad in vitro spectrum (which does not by itself prove clinical efficacy): gram-positives such as Streptococcus pneumoniae and Staph. aureus; gram-negatives such as Haemophilus influenzae; plus Bartonella spp., Bordetella spp., Mycoplasma pneumoniae, Borrelia burgdorferi and Toxoplasma spp. Its defining property is extensive tissue sequestration — tissue concentrations greatly exceed serum, giving a long tissue half-life that supports short courses and extended dosing intervals.

## Formulations and products

- Azithromycin 250 mg tablet
- Azithromycin oral suspension 40 mg/mL (200 mg/5 mL after reconstitution — Plumb’s p.139)
- Azithromycin 500 mg powder vial reconstituted to 100 mg/mL (sterile water) — dilute further before IV infusion (Plumb’s p.138–139)

## Before you use this dose

> **Caution:** Reference doses for veterinary professionals. Confirm the dose against the product label, the patient’s condition, current guidance and local regulations before use; the attending veterinarian remains responsible for every clinical decision.

## Other antibiotics

- [Amoxicillin](https://vetmasterji.com/drugs/amoxicillin)
- [Amoxicillin / Clavulanic Acid](https://vetmasterji.com/drugs/amoxicillin-clavulanate)
- [Ampicillin](https://vetmasterji.com/drugs/ampicillin)
- [Apramycin](https://vetmasterji.com/drugs/apramycin)
- [Cefadroxil](https://vetmasterji.com/drugs/cefadroxil)
- [Cefazolin](https://vetmasterji.com/drugs/cefazolin)
- [Cefixime](https://vetmasterji.com/drugs/cefixime)
- [Cefoperazone](https://vetmasterji.com/drugs/cefoperazone)

## Frequently asked questions

### What is the dose of Azithromycin for dogs?

Reference doses for Azithromycin in dogs: 5–10 mg/kg PO q24h × 2–5 d then q48–72h (Respiratory / soft-tissue infection). Confirm against the label and the patient before use.

### What is the dose of Azithromycin for cats?

Reference doses for Azithromycin in cats: 5–10 mg/kg PO q24h × 3 d then q72h (Bartonella / Chlamydophila / URI). Confirm against the label and the patient before use.

### What is the dose of Azithromycin for horses?

Reference doses for Azithromycin in horses: 10 mg/kg PO q24h for 5 days, then q48h (Foal R. equi pneumonia). Confirm against the label and the patient before use.

### When should Azithromycin not be used?

Macrolide hypersensitivity. Hepatic impairment (hepatic metabolism). Caution with QT-prolonging drugs. Adult horses — risk of severe diarrhoea (reserve for foals).

### What are the side effects of Azithromycin in animals?

GI upset — vomiting, diarrhoea; Hepatic enzyme elevation; Foal hyperthermia / diarrhoea.

## Sources

- Plumb's Veterinary Drug Handbook
- Papich, Papich Handbook of Veterinary Drugs, 5th edition

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VetMasterJi is a clinical decision-support and education platform for veterinary professionals and students. It does not provide veterinary advice, diagnosis or treatment for specific animals. All drug doses, calculators and differentials are references that must be independently verified before clinical use; the attending registered veterinarian remains solely responsible for every clinical decision.