Fenbendazole
Fenbendazole is a highly effective, broad-spectrum **benzimidazole anthelmintic** widely used in veterinary medicine across multiple species. **Key Clinical Features:** * **Nematode Efficacy:** Highly effective against gastrointestinal roundworms, hookworms, and whipworms. * **Cestode Efficacy:** Effective against *Taenia* species tapeworms, but **not** effective against the common flea tapeworm (*Dipylidium caninum*). * **Protozoal Efficacy:** Considered a first-line treatment for **Giardia** infections in dogs and cats. * **Respiratory Parasites:** Frequently utilized for various lungworm infections (e.g., *Aelurostrongylus*, *Capillaria*, *Paragonimus*). **Clinical Pearl:** Fenbendazole has an exceptionally wide margin of safety and is considered the drug of choice for treating parasitic infections, including Giardia, in pregnant animals.
กลไกการออกฤทธิ์: Fenbendazole is a **time-dependent** antiparasitic agent, which is why multi-day dosing is typically required in small animals. * **Primary Mechanism:** It selectively binds to parasite **β-tubulin** → prevents tubulin polymerization → inhibits **microtubule formation**. This disrupts essential intracellular transport mechanisms within the parasite. * **Secondary Mechanism:** At higher concentrations, it disrupts metabolic pathways by inhibiting key enzymes such as **fumarate reductase** and **malate dehydrogenase** → depletes ATP/energy reserves → parasite death.
ขนาดยาตามชนิดสัตว์
- For susceptible parasites · 5 mg/kg in feed for 3 days · PO · q24h · 3 days
- CAMELIDS: For susceptible parasites in new world camelids · 10-20 mg/kg PO for 3-5 days · PO · q24h · 3-5 days
- CAMELIDS: For adjunctive treatment of meningeal worm infestation (Parelaphostrongylus tenius) · Fenbendazole 50 mg/kg PO for 5 days with ivermectin 0.3 mg/kg SC for 5 days. · PO · q24h · 5 days · Also use prophylactic treatment for stress ulcers, anti-inflammatories, fluids, nutritional support, etc.
- For susceptible parasites · 5 mg/kg in feed for 3 days · PO · q24h · 3 days
- For susceptible ascarids, hookworms, strongyloides, and tapeworms (Taenia spp. only) · 50 mg/kg, PO for 5 days · PO · q24h · 5 days
- For Giardia · 50 mg/kg PO once daily for 3 consecutive days; if this does not clear the infection, a longer course of therapy (5-7 days) is used · PO · q24h · 3-7 days
- For Giardia · 50 mg/kg PO q24h for 3-5 days · PO · q24h · 3-5 days
- For lungworms (Aelurostrongylus abstrusus) · 25-50 mg/kg q12h for 10-14 days · PO · q12h · 10-14 days
- For lungworms (Aelurostrongylus abstrusus) · 50 mg/kg, PO for 10 days · PO · q24h · 10 days
วิธีการให้ยา
ข้อห้ามใช้
- Not FDA-approved for use in horses intended for food purposes
อาการไม่พึงประสงค์
- Hypersensitivity reactions (secondary to antigen release by dying parasites)
- Salivation (infrequent)
- Vomiting (infrequent)
- Diarrhea (infrequent)
- Pancytopenia (rarely reported in dogs)
- Bone marrow hypoplasia (rarely reported in dogs)
อันตรกิริยาระหว่างยา
- Bromsalan flukicides (dibromsalan, tribromsalan) · Abortions in cattle and death in sheep have been reported after concurrent use
การติดตาม
- Fecal examinations to confirm parasite clearance
- Monitor for hypersensitivity reactions if treating heavy parasite burdens
- Fecal examination for parasite clearance
- Complete blood count (CBC) if bone marrow hypoplasia is suspected
การได้รับยาเกินขนาด
Fenbendazole is exceptionally well tolerated, even at doses up to **100X the recommended dose**. * The LD50 in laboratory animals exceeds 10 grams/kg when administered orally. * It is highly unlikely that an acute overdosage would lead to any significant clinical signs.
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