Penicillin Dosage for Dogs with Lyme Disease: A Comprehensive Guide

Important: Penicillin is not first-line for canine Lyme disease. Doxycycline is standard. Penicillin may be used in specific circumstances (e.g., doxycycline intolerance, pregnancy). Always follow veterinary prescription.

Penicillin G Procaine (Common Injectable Form)

• Dosage: 20,000–40,000 IU/kg (9,000–18,000 IU/lb) IM or SC
• Frequency: Every 24 hours
• Duration: 14–28 days (typically 30 days for Lyme)

Penicillin V (Oral) — Rarely Used for Lyme

• Poor bioavailability in dogs; not recommended for systemic borreliosis.

First-Line: Doxycycline

• Dosage: 5–10 mg/kg (2.3–4.5 mg/lb) PO q12h
• Duration: 30 days minimum
• Advantages: Oral, intracellular penetration, anti-inflammatory, covers co-infections (Anaplasma, Ehrlichia).

Alternatives if Doxycycline Contraindicated

• Amoxicillin: 20 mg/kg PO q12h × 30 days (good for pregnant/nursing dogs).
• Cefovecin (Convenia): 8 mg/kg SC single injection (lasts 14 days); repeat as needed. Convenient but expensive.
• Azithromycin: 10 mg/kg PO q24h × 30 days (less evidence).

Critical Considerations

• Diagnosis confirmation: C6 antibody (SNAP 4Dx) + clinical signs + exposure history.
• Pain management: NSAIDs (carprofen, meloxicam) for joint pain.
• Monitoring: Recheck C6 at 6 months; quantitative drop indicates response.
• Prevention: Tick control (isoxazolines, collars), vaccination (controversial), prompt tick removal.

Never use human penicillin for dogs. Formulations, dosing, and safety differ. Veterinary oversight is mandatory.