Vet’s 2025 Guide to Doxycycline Use in Horses – by Dr Duncan Houston
In this article
💊 Vet’s 2025 Guide to Doxycycline Use in Horses
By Dr Duncan Houston BVSc
1. What Is Doxycycline? 🧪
Doxycycline is a broad-spectrum **tetracycline antibiotic** commonly used off-label in horses to treat various bacterial infections, including tick-borne diseases like Lyme and anaplasmosis, respiratory infections, and joint/soft tissue infections when other antibiotics fail :contentReference[oaicite:3]{index=3}.
2. Why Choose Doxycycline
- Highly effective against intracellular pathogens (e.g., Anaplasma, Borrelia) :contentReference[oaicite:4]{index=4}
- Good oral bioavailability when given on an empty stomach :contentReference[oaicite:5]{index=5}
- Bacteriostatic, reducing toxin load and inflammation — potential anti-MMP effects (though primarily in humans) :contentReference[oaicite:6]{index=6}
3. Common Indications
- Lyme disease: 10 mg/kg PO every 12 h for 1–2 months :contentReference[oaicite:7]{index=7}
- Anaplasmosis: 10 mg/kg PO every 12 h for 10–14 days :contentReference[oaicite:8]{index=8}
- Pneumonia/respiratory infections in foals or adults
- Joint and soft tissue infections in combination therapy :contentReference[oaicite:9]{index=9}
- Eye infections (keratomycosis): supports therapeutic levels in tear film at 20 mg/kg daily :contentReference[oaicite:10]{index=10}
4. Dosing & Administration Tips
| Indication | Dose | Frequency | Feeding |
|---|---|---|---|
| Lyme, anaplasmosis | 10 mg/kg | PO q12 h | Empty stomach (bowel rest) |
| Respiratory/joint | 10 mg/kg PO q12–24 h | Empty stomach preferred | |
| Corneal support | 20 mg/kg PO q24 h | High-dose once daily | Empty stomach :contentReference[oaicite:11]{index=11} |
Give on empty stomach for best absorption; withhold food 8 h before and 2 h after dosing :contentReference[oaicite:12]{index=12}. Compounded liquid can ease administration to medicine-averse horses :contentReference[oaicite:13]{index=13}.
5. Absorption & Pharmacokinetics
Though absorption can be variable, PO dosing at 20 mg/kg achieves therapeutic plasma levels sufficient for many infections :contentReference[oaicite:14]{index=14}. Plasma drug reaches tear film—useful for ocular infections :contentReference[oaicite:15]{index=15}.
6. Potential Side Effects
- Diarrhea or colitis—monitor GI function :contentReference[oaicite:16]{index=16}
- Loss of appetite, mild kidney stress if dehydrated :contentReference[oaicite:17]{index=17}
- Esophageal irritation if capsules lodge before water intake (humans, but good practice to follow with water in large animals) :contentReference[oaicite:18]{index=18}
- Avoid in pregnancy — may affect bone/cartilage development :contentReference[oaicite:19]{index=19}
7. Contraindications & Cautions
- Avoid IV use: serious cardiovascular complications described, including collapse and death :contentReference[oaicite:20]{index=20}
- Caution in horses with liver/renal disease :contentReference[oaicite:21]{index=21}
- Avoid in pregnant or growing horses due to potential bone/teeth impact :contentReference[oaicite:22]{index=22}
8. Monitoring & Safety
- Check hydration, appetite, body weight regularly
- Watch for signs of colitis or digestive upset
- For long courses or high doses, periodic bloodwork (CBC, renal & liver enzymes)
- End therapy if severe GI signs or decreased appetite occur
- Ensure full course compliance—skipped doses may worsen resistance :contentReference[oaicite:23]{index=23}
9. Drug Interactions
- Absorption reduced with calcium, magnesium, antacids—avoid co-dosing
- May interact with feed minerals and supplements
- Human exposure caution: gloves advised; pregnant staff avoid contact :contentReference[oaicite:24]{index=24}
10. Emergency & Overdose Response
- Minimal toxicity with overdose—monitor for diarrhea, colic, appetite loss :contentReference[oaicite:25]{index=25}
- Provide fluids, electrolytes, and symptomatic supportive care
- Contact vet or poison control if concerns escalate
11. Ask A Vet Support 🩺
With Ask A Vet, we assist owners with:
- Customized dosing schedules and reminders
- Monitoring side effects & arranging laboratory work
- Troubleshooting GI issues and hydration
- Adjusting doses for conditions like kidney/liver disease
- Transition support for ocular, respiratory, tick-borne, or joint infections
Download the Ask A Vet app for expert antibiotic guidance, monitoring tools, and安心 telemedicine support in 2025! ❤️
12. Quick Reference Table
| Use | Dose | Frequency | Key Notes |
|---|---|---|---|
| Lyme/anaplasmosis | 10 mg/kg | q12 h | Empty stomach |
| Respiratory/joint | 10 mg/kg | q12–24 h | Watch GI |
| Corneal support | 20 mg/kg | q24 h | Verify tear levels |
| Side effects | N/A | GI, appetite, renal stress | |
| Contraindications | N/A | No IV, no pregnancy |
13. Final Thoughts
Doxycycline is a versatile, effective antibiotic for many equine infections when used properly. With optimal dosing, careful monitoring, and veterinary collaboration—especially via telehealth—horses can recover reliably. For thorough guidance through treatment and follow-up, trust Ask A Vet to support your care every step of the way. 🐴💊
