Vet Guide to Fenbendazole in 2025 🐾

Hello, I’m **Dr Duncan Houston, BVSc**, founder of Ask A Vet. In this comprehensive guide, we'll dive deep into **fenbendazole**, known as Panacur® or Safe‑Guard®, a trusted benzimidazole dewormer for horses. You'll learn how it works, when and how to use it effectively (including for encysted small strongyles), proper dosing, safety tips, hypersensitivity reactions, and strategies to reduce parasite resistance. 💊🐴

📘 What Is Fenbendazole?

Fenbendazole is a benzimidazole-class anthelmintic that disrupts parasite energy metabolism by inhibiting microtubule formation—effective against adult and larval stages of strongyles, ascarids, pinworms, and encysted larvae :contentReference[oaicite:3]{index=3}.

✅ Approved Uses

• Control of large strongyles, small strongyles, pinworms, and roundworms in horses :contentReference[oaicite:4]{index=4}.
• Labeled larvicidal dose (5 days) for encysted small-strongyle larvae—only FDA-approved option :contentReference[oaicite:5]{index=5}.
• Safe for foals, pregnant mares, older horses at standard dosing :contentReference[oaicite:6]{index=6}.

📐 Dosing & Administration

• **Standard dose:** 5 mg/kg (2.3 mg/lb) orally—single dose via paste on back of tongue after fasting :contentReference[oaicite:7]{index=7}.
• **Foals/weanlings/ascarids:** 10 mg/kg (4.6 mg/lb) as a single dose :contentReference[oaicite:8]{index=8}.
• **Encysted larvae:** Administer 10 mg/kg daily for 5 consecutive days (“PowerPac” protocol) :contentReference[oaicite:9]{index=9}.
• Ensure mouth is empty and weight is accurate; paste or tube equally effective :contentReference[oaicite:10]{index=10}.

⚠️ Safety, Side Effects & Hypersensitivity

• Well tolerated: safety margin wide—even at 1000 mg/kg single dose or 50 mg/kg daily for 15 days :contentReference[oaicite:11]{index=11}.
• Occasional hypersensitivity reactions due to parasite die-off: hives, respiratory signs, colic, diarrhea, rare shock—seek vet care if seen :contentReference[oaicite:12]{index=12}.
• No contraindications for use in horses; tested safe in pregnant mares and stallions at standard doses—caution with encysted-strongyle protocol in pregnant horses :contentReference[oaicite:13]{index=13}.

🚫 Resistance & Strategic Deworming

• Overuse may drive resistance—rotate drug classes and base decisions on fecal egg counts :contentReference[oaicite:14]{index=14}.
• Strategic larvicidal dosing in spring and fall targets encysted small strongyles when pasture contamination is low :contentReference[oaicite:15]{index=15}.
• Perform fecal egg count reduction tests regularly to assess treatment efficacy :contentReference[oaicite:16]{index=16}.

🩺 Monitoring & Follow‑Up

• Watch for mild colic or hypersensitivity signs post-dosing.
• Perform fecal egg counts 10–14 days after treatment to confirm worm clearance :contentReference[oaicite:17]{index=17}.
• Adjust future parasite control based on fecal results and pasture management :contentReference[oaicite:18]{index=18}.

🏡 Real‑World Scenarios

🥕 Pasture adult horse

• A 500 kg horse receives single 5 mg/kg dose spring treatment—parasite egg counts dropped to zero; monitored again in fall with larvicidal dosing as needed.

🍼 Foal with ascarids

• A 200 kg foal dewormed at 10 mg/kg; follow-up fecal was clear in 2 weeks with no adverse signs.

❓ FAQs

Why larvicidal 5-day protocol?

Encysted small strongyles don’t respond to single dose; only larvicidal fenbendazole 10 mg/kg daily for 5 days kills them :contentReference[oaicite:19]{index=19}.

Can I use paste vs. tube?

Yes—both forms deliver accurately when properly administered; ensure horse’s mouth is empty :contentReference[oaicite:20]{index=20}.

Safe in pregnant mares?

Yes at standard single dose; larvicidal protocol not fully tested in pregnant horses—consult your vet first :contentReference[oaicite:21]{index=21}.

What if resistance suspected?

Use fecal egg count reduction tests to confirm; if resistance present, rotate to a different dewormer class and adjust protocol :contentReference[oaicite:22]{index=22}.

📌 Final Takeaways

• Fenbendazole (Panacur®/Safe‑Guard®) is a broad-spectrum horse dewormer safe at 5 mg/kg and larvicidal at 10 mg/kg × 5 days.
• Well-tolerated, with rare hypersensitivity from parasite die-off—be vigilant.
• Use larvicidal protocol strategically (spring/fall) to target encysted larvae.
• Combine fecal testing with rotational deworming to prevent resistance.
• Ensure accurate dosing, empty stomach administration, and monitor fecal egg counts to keep horses strong and pasture healthy in 2025 and beyond. 🐴❤️

Thinking of fenbendazole for your horse’s deworming plan? Download the Ask A Vet app for weight-based dosing calculators, fecal tracking, treatment reminders, and 24/7 veterinary support—so your equine partner stays healthy year-round. 🐾