Clarithromycin: veterinary dose and monograph

At a glance

Drug class

Antibiotic

Also known as

Klacid, Claribid, Clarith

Species with doses

Dogs, Cats, Horses and Ferrets

General dose range

5–10 mg/kg PO q12h — check the species tables for the indication

Routes

PO

Last reviewed

1 October 2026

Indications

• Rhodococcus equi pneumonia in foals (with rifampin)
• Feline atypical mycobacterial / leproid infections
• Helicobacter-associated gastritis (multidrug regimen)
• Susceptible Gram-positive / intracellular respiratory infections

Clarithromycin 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

• Susceptible infection / Helicobacter: Papich 5e: 7.5 mg/kg q12h PO. Plumb’s p.285: 5–10 mg/kg PO q12h (Greene & Watson); 2.5–10 mg/kg twice daily (Boothe).
• Canine leproid granuloma (with rifampin): Plumb’s p.285 (Malik 2001): 15–25 mg/kg total daily dose divided q8–12h with rifampin 10–15 mg/kg once daily, until lesions resolve. (= 7.5–12.5 mg/kg q12h.)

Cats

• Atypical mycobacteria / leproid syndrome: Papich 5e and Plumb’s p.285: 7.5 mg/kg PO q12h; H. pylori 7.5 mg/kg twice daily with metronidazole and amoxicillin for 14 days. Feline leprosy: 62.5 mg per cat q12h with clofazimine and/or rifampin (Malik 2002); Nocardia 62.5–125 mg per cat twice daily in combination; M. bovis-variant 5–10 mg/kg q12h with rifampin and enrofloxacin for ≥2 months.

Horses

• Rhodococcus equi pneumonia (FOALS, with rifampin): Papich 5e and Plumb’s p.285 (Jacks 2002; Giguere 2003): foals 7.5 mg/kg PO q12h, usually with rifampin 5 mg/kg q12h or 10 mg/kg q24h. Foals only — macrolides can cause fatal colitis in adult horses.

Ferrets

• Helicobacter mustelae / mycobacteria (triple therapy): Plumb’s p.285: 12.5 mg/kg PO q12h (or q8h) with ranitidine bismuth citrate 24 mg/kg q12h for 14 days (Johnson-Delaney 2009); 12.5–50 mg/kg q8–24h with omeprazole 0.7 mg/kg once daily (Fisher 2005).

Contraindications

Adult horses / hindgut fermenters (fatal colitis — macrolide class). Macrolide hypersensitivity. Significant hepatic impairment. Concurrent drugs heavily dependent on CYP3A (see interactions) or QT-prolonging agents. Known hypersensitivity.

Species-specific warnings

Horses: Foals only (Rhodococcus). Fatal antibiotic-associated colitis in adult horses; handlers should note foal-to-dam transmission risk during treatment.

Rabbits: Do not use in rabbits — fatal enterotoxaemia.

Adverse effects

• GI upset (vomiting, diarrhoea) — less than erythromycin
• Hepatotoxicity (uncommon)
• QT prolongation at high dose
• Fatal colitis in adult horses/hindgut fermenters
• Pink/red urine or skin discolouration when combined with rifampin (from rifampin)

Drug interactions

• Potent CYP3A4 inhibitor: raises cyclosporine, cisapride, midazolam, digoxin, theophylline, statin levels — toxicity risk
• QT-prolonging drugs: additive arrhythmia risk
• Rifampin (used together for Rhodococcus): mutually alters levels — established combination but monitor
• Antacids: minor effect on absorption

Pregnancy and lactation

Limited veterinary data; some macrolides preferred over clarithromycin in pregnancy. Use if clearly indicated.

Monitoring

• GI tolerance and clinical response
• Liver enzymes on long courses
• Levels/effects of interacting CYP3A drugs
• Foal/dam colitis surveillance during Rhodococcus protocols

Toxicity and overdose

Better tolerated than erythromycin; overdose causes GI upset and, at high dose, QT prolongation and hepatic effects. Catastrophic colitis if given to adult horses/hindgut fermenters.

Management: Supportive — fluids, anti-emetic; ECG if very high dose; hepatoprotection if hepatotoxicity. Discontinue and treat colitis aggressively in equids. No specific antidote.

Clinical pearls

• A better-tolerated, twice-daily macrolide than erythromycin — favoured for foal Rhodococcus (with rifampin) and feline atypical mycobacterial disease
• Strong CYP3A inhibitor — review co-medications (cyclosporine, cisapride, theophylline) before combining
• Never give to adult horses or rabbits — fatal colitis
• Highly lipophilic and intracellular — good for the intracellular pathogens it targets

Mechanism of action

Binds the 50S ribosomal subunit (23S rRNA), blocking translocation during protein synthesis — bacteriostatic to bactericidal depending on organism/concentration. Its 6-O-methyl modification improves acid stability, oral absorption and intracellular penetration over erythromycin, which suits intracellular pathogens (Rhodococcus, mycobacteria). It is a strong CYP3A4 inhibitor.

Formulations and products

• 250 mg tablet
• 500 mg tablet
• Oral suspension 25 mg/mL (125 mg/5 mL)
• Klacid — 250 / 500 mg tablet; 125 mg/5 mL suspension, Tablet / suspension (human-label)
• Claribid — 250 / 500 mg tablet, Tablet (human-label)

Storage

Tablets: 15–30 °C, dry. Suspension: per label (often room temperature once reconstituted — do NOT refrigerate certain brands; shake well).

Before you use this dose

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

• Cefuroxime
• Cephalexin
• Chloramphenicol
• Ciprofloxacin
• Clindamycin
• Cloxacillin
• Colistin (Polymyxin E)
• Danofloxacin

Frequently asked questions