作用機制: 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.
各物種劑量
Sheep
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.
Goats
For susceptible parasites · 5 mg/kg in feed for 3 days · PO · q24h · 3 days
Cats
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
給藥途徑
PO
禁忌症
Not FDA-approved for use in horses intended for food purposes
不良反應
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)
藥物相互作用
Bromsalan flukicides (dibromsalan, tribromsalan) · Abortions in cattle and death in sheep have been reported after concurrent use
監測
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
過量
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.
For lungworms (Aelurostrongylus abstrusus) · 20 mg/kg PO once daily for 5 days; repeat in 5 days · PO · q24h · 5 days, repeat in 5 days
For lungworms (Capillaria aerophilia) · 50 mg/kg, PO for 10 days · PO · q24h · 10 days
For lungworms (Capillaria aerophilia) · 50 mg/kg PO once daily for 10-14 days · PO · q24h · 10-14 days
For Capillaria feliscati · 25 mg/kg, twice daily PO for 3-10 days · PO · q12h · 3-10 days
For Capillaria feliscati · 25 mg/kg, PO q12h for 10 days · PO · q12h · 10 days
For Paragonimus kellicotti · 25-50 mg/kg PO twice daily for 10-14 days · PO · q12h · 10-14 days
For Paragonimus kellicotti · 50 mg/kg PO once daily for 10-14 days · PO · q24h · 10-14 days
For Eurytrema procyonis (pancreatic fluke) · 30 mg/kg, PO daily for 6 days · PO · q24h · 6 days
LARGE (EXOTIC) CATS: For labeled parasites · 10 mg/kg PO once daily for 3 consecutive days. · PO · q24h · 3 days
Cattle
For removal/control of Haemonchus contortus, Ostertagia ostertagi, Trichostrongylus axei, Bunostomum phlebotomum, Nematodirus helvetianus, Cooperia spp., Trichostrongylus colubriformis, Oesophagostomum radiatum, and Dictyocaulus vivaparus · 5 mg/kg, PO · PO · Once
For removal/control of Haemonchus contortus, Ostertagia ostertagi, Trichostrongylus axei, Bunostomum phlebotomum, Nematodirus helvetianus, Cooperia spp., Trichostrongylus colubriformis, Oesophagostomum radiatum, and Dictyocaulus vivaparus · 7.5 mg/kg, PO · PO · Once
For removal/control of Haemonchus contortus, Ostertagia ostertagi, Trichostrongylus axei, Bunostomum phlebotomum, Nematodirus helvetianus, Cooperia spp., Trichostrongylus colubriformis, Oesophagostomum radiatum, and Dictyocaulus vivaparus · 4 mg/kg PO; under conditions of continuous exposure to parasites, animals may need to be retreated after 4-6 weeks · PO · Once
For Moniezia spp., and arrested 4th stage forms of Ostertagia ostertagi · 10 mg/kg, PO · PO · Once
For giardiasis in calves · 15 mg/kg PO for 3 successive days · PO · q24h · 3 days · Move to a pen thoroughly cleaned and disinfected with 10% ammonia after treatment.
Horses
For control of large and small strongyles, and pinworms in adult horses · 5 mg/kg PO · PO · Once
For foals and weanlings (less than 18 months of age) where ascarids are a common problem · 10 mg/kg PO · PO · Once
For control of encysted early 3rd stage, late 3rd stage and 4th stage cyathostome larvae and 4th stage Strongylus vulgaris larvae · 10 mg/kg PO for 5 consecutive days. · PO · q24h · 5 days
For treatment of migrating large strongyles · 50 mg/kg PO for 3 consecutive days, or 10 mg/kg for 5 consecutive days · PO · q24h · 3 or 5 days
For mucosal stage of small strongyles · 7.5-10 mg/kg PO once daily for 5 days; a single dose of 30 mg/kg is effective against older encysted stages · PO · q24h · 5 days (or once for 30 mg/kg dose)
Birds
For Ascarids · 10-50 mg/kg PO once; repeat in 10 days. · PO · Once · Repeat in 10 days · Do not use during molt (may cause stunted feathers) or while nesting.
For flukes or microfilaria · 10-50 mg/kg PO once daily for 3 days · PO · q24h · 3 days
For Capillaria · 10-50 mg/kg PO once daily for 5 days. · PO · q24h · 5 days · Is not effective against gizzard worms in finches.
For nematodes, some trematodes · 10-50 mg/kg PO once daily for 3-5 days; 20-100 mg/kg oral single dose range; 125 mg/L of drinking water for 5 days (50 mg/L for 5 days in finches); or 100 mg/kg of feed for 5 days. · PO · Varies · 3-5 days · Not recommended to be used in breeding season during molting.
Ratites: Has efficacy against ostrich tapeworm (Houttuynia struthionus) · 15 mg/kg PO once daily for 3 days. · PO · q24h · 3 days
Swine
For susceptible parasites · 5 mg/kg PO; 3 mg/kg in feed for 3 days; 10 mg/kg for ascarids · PO · Varies · 3 days (if in feed)
For whipworms in potbellied pigs · 9 mg/kg PO for days · PO · q24h · Unspecified days
SmallMammals
For pinworms in mice, rats, hamsters, gerbils and rabbits · 50 mg/kg PO once · PO · Once
For Giardia in Chinchillas · 25 mg/kg PO once a day for 3 days · PO · q24h · 3 days
Mice, Rats, Gerbils, Hamsters, Guinea pigs, Chinchillas · 20-50 mg/kg PO once daily for 5 days · PO · q24h · 5 days · Higher dose is for Giardia
BEARS (URSIDAE): For labeled parasites · 10 mg/kg PO once daily for 3 consecutive days. · PO · q24h · 3 days
Dogs
For susceptible ascarids, hookworms, whipworms, and tapeworms (Taenia spp. only) · 50 mg/kg, PO for 3 consecutive days · PO · q24h · 3 days
For susceptible ascarids, hookworms, whipworms, and tapeworms (Taenia spp. only) · 55 mg/kg, PO for 3 days (5 days for Taenia) · PO · q24h · 3-5 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
To prevent transplacental and transmammary transmission of somatic T. canis and A. caninum · 50 mg/kg PO once daily from the 40th day of gestation to the 14th day of lactation. · PO · q24h · From day 40 of gestation to day 14 of lactation
For Capillaria plica · 50 mg/kg once daily for 3 days; repeat a single 50 mg/kg dose 3 weeks later · PO · q24h · 3 days, then single dose 3 weeks later
For Capillaria plica · 50 mg/kg, PO daily for 3-10 days · PO · q24h · 3-10 days
For Capillaria aerophilia · 25-50 mg/kg q12h for 10-14 days · PO · q12h · 10-14 days
For Capillaria aerophilia · 50 mg/kg PO once daily for 10-14 days · PO · q24h · 10-14 days
For Filaroides hirthi · 50 mg/kg, PO once daily for 14 days. · PO · q24h · 14 days · Symptoms may worsen during therapy, presumably due to a reaction when the worm dies.
For Filaroides hirthi · 50 mg/kg PO once daily for 10-14 days · PO · q24h · 10-14 days
For Paragonimus kellicotti · 25-50 mg/kg PO twice daily for 10-14 days · PO · q12h · 10-14 days
For Paragonimus kellicotti · 50 mg/kg PO once daily for 10-14 days · PO · q24h · 10-14 days
For Paragonimus kellicotti · 50 mg/kg, PO once daily for 3 consecutive days; repeat in 2-3 weeks and again in 2 months · PO · q24h · 3 days, repeat at 2-3 weeks and 2 months
For Crenosoma vulpis · 50 mg/kg PO once daily for 3 days · PO · q24h · 3 days
For Eucoleus boehmi · 50 mg/kg PO once daily for 10-14 days · PO · q24h · 10-14 days · Improvement may only be temporary
Reptiles
For susceptible infections (most species) · 50-100 mg/kg PO once; repeat in 2-3 weeks · PO · Once · Repeat in 2-3 weeks · Very effective against Strongyloides.