🪱 Fenbendazole (Panacur®/Safe‑Guard®) Vet Guide 2025 by Dr Duncan Houston

Fenbendazole, sold as Panacur® and Safe‑Guard®, is a cornerstone of equine parasite control. In this detailed guide, Dr Duncan Houston explains its mechanisms, when and how to use it (including larvicidal “PowerPac” courses), how to manage resistance, and safety considerations to ensure your horses stay healthy. 🐎✨

1. What Is Fenbendazole? 🤓

Fenbendazole is a broad-spectrum benzimidazole dewormer used across multiple species, including horses, cattle, swine, goats, dogs, cats, and even exotic animals :contentReference[oaicite:3]{index=3}. Branded as Panacur® (prescription) and Safe‑Guard® (OTC), both contain 10 % fenbendazole—100 mg per gram of paste :contentReference[oaicite:4]{index=4}.

2. How It Works

• It disrupts parasite energy production by binding parasite β-tubulin, blocking glucose uptake and causing death :contentReference[oaicite:5]{index=5}.
• It’s selectively more harmful to parasites than to the horse’s own cells :contentReference[oaicite:6]{index=6}.

3. Indications in Horses

Effective against:

• Large strongyles (Strongylus spp.), small strongyles including encysted larvae, pinworms, ascarids, and larval migrans of S. vulgaris :contentReference[oaicite:7]{index=7}.
• Encysted small strongyles and L4‑stage larvae—most benzimidazoles do not cover these but Panacur “PowerPac” larvicidal course does :contentReference[oaicite:8]{index=8}.

4. Dosing Protocols

Do not underdose—under-dosing encourages resistance :contentReference[oaicite:9]{index=9}.

5. Resistance & Strategic Use

• Fenbendazole resistance is common in small strongyles; small strongyle egg counts help guide use :contentReference[oaicite:10]{index=10}.
• Larvicidal courses (PowerPac) should be rotated and used only when needed and following a fecal egg count reduction test.
• Maintain pasture hygiene and frequent monitoring to minimize drug pressure :contentReference[oaicite:11]{index=11}.

6. Safety & Side Effects

Fenbendazole is generally safe:

• Tolerated in foals, pregnant mares, seniors, and debilitated horses at labeled doses :contentReference[oaicite:12]{index=12}.
• High-dose or prolonged courses may release antigens from dying parasites, triggering hypersensitivity reactions—monitor for colic, urticaria, tachypnea :contentReference[oaicite:13]{index=13}.
• No documented teratogenic or reproductive toxicity at labeled doses :contentReference[oaicite:14]{index=14}.

7. Administration Tips

• Weight-based dosing—use accurate scales to avoid under- or overdosing.
• Ensure mouth is empty and paste is given at back of tongue.
• Repeat larvicidal high-dose (PowerPac) precisely as labeled for 5 days.

8. Monitoring & Vet Collaboration

• Perform fecal egg counts before and 10–14 days after treatment to assess efficacy.
• Rotate dewormers based on resistance data and veterinary advice.
• Use fecal egg reduction tests annually, particularly after larvicidal treatments.

9. Storage & Safety Notes

• Store syrup or paste at room temperature below 77 °F (25 °C), protected from moisture :contentReference[oaicite:15]{index=15}.
• Not safe for horses intended for human consumption.
• Follow all packaging and disposal guidelines carefully.

10. Clinical Summary Table

🔚 Final Thoughts

Fenbendazole paste remains a versatile and vital tool for equine parasite management. Its larvicidal “PowerPac” dose is especially valuable—but prudent use and resistance monitoring are crucial to preserve effectiveness. Accurate dosing, fecal testing, pasture hygiene, and veterinary partnerships ensure safe and lasting parasite control. Need help building a deworming plan, tracking fecal counts, or analyzing resistance? Contact our Ask A Vet team. Download the Ask A Vet app for personalized parasite management, treatment logs, and 24/7 expert support. 🌟