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Fenbendazole

The Elephant Formulary
© 2003-06 Susan K. Mikota DVM and Donald C. Plumb, Pharm.D.
Published by Elephant Care International -
www.elephantcare.org


Elephant specific information, if available, is in blue.

Chemistry - A benzimidazole anthelmintic, fenbendazole occurs as a white, crystalline powder. It is only slightly soluble in water.

 

Storage/Stability/Compatibility - Fenbendazole products should be stored at room temperature.

 

Uses/Indications - Fenbendazole is indicated (labeled) for the removal of the following parasites in dogs: ascarids (Toxocara canis, T. leonina), Hookworms (Ancylostoma caninum, Uncinaria stenocephala), whipworms (Trichuris vulpis), and tapeworms (Taenia pisiformis). It is not effective against Dipylidium caninum. Fenbendazole has also been used clinically to treat Capillaria aerophilia:, Filaroides hirthi and Paragonimus kellicoti infections in dogs.

 

Fenbendazole is indicated (labeled) for the removal of the following parasites in cattle: Adult forms of: Haemonchus contortus, Ostertagia ostertagi, Trichostrongylus axei, Bunostomum phlebotomum, Nematodirus helvetianus, Cooperia spp., Trichostrongylus colubriformis, Oesophagostomum radiatum and Dictyocaulus vivaparus. It is also effective against most immature stages of the above listed parasites. Although not approved, it also has good activity against Moniezia spp., and arrested 4th stage forms of Ostertagia ostertagi.

 

Fenbendazole is indicated (labeled) for the removal of the following parasites in horses: large strongyles (S. edentatus, S. equinus, S. vulgaris), small strongyles (Cyathostomum spp., Cylicocylus spp., Cylicostephanus spp.,Triodontaphorus spp.) and pinworms (Oxyuris equi).

 

Fenbendazole is indicated (labeled) for the removal of the following parasites in swine: large roundworms (Ascaris suum), lungworms (Metastrongylus apri), nodular worms (Oesphagostomum dentatum, O. quadrispinulatum), small stomach worms (Hyostrongylus rubidus), whipworms (Trichuris suis) and kidney worms (Stephanuris dentatus; both mature and immature).

 

Although not approved, fenbendazole has been used in cats, sheep, goats, pet birds and llamas. See Dosage section for more information.

 

Fenbendazole is considered to be safe to use in pregnant bitches and is generally considered to be safe to use in pregnancy for all species.

 

Pharmacokinetics - Fenbendazole is only marginally absorbed after oral administration. After oral dosing in calves and horses, peak blood levels of 0.11 micrograms/ml and 0.07 micrograms/ml respectively, were measured. Absorbed fenbendazole is metabolized (and vice-versa) to the active compound, oxfendazole (sulfoxide) and the sulfone. In sheep, cattle, and pigs, 44-50% of a dose of fenbendazole is excreted unchanged in the feces, and <1% in the urine.

 

Contraindications/Precautions - Fenbendazole is not approved for use in lactating dairy cattle or for horses intended for food purposes.

 

Adverse Effects/Warnings - At usual doses, fenbendazole generally does not cause any adverse effects. Hypersensitivity reactions secondary to antigen release by dying parasites may occur; particularly at high dosages. Vomiting may infrequently occur in dogs or cats receiving fenbendazole.

 

Single doses (even at exaggerated doses) are not effective in dogs and cats; must treat for 3 days.

 

Overdosage/Toxicity - Fenbendazole is apparently well tolerated at doses up to 100X recommended. The LD50 in laboratory animals exceeds 10 grams/kg when administered PO. It is unlikely an acute overdosage would lead to clinical symptoms.

 

Drug Interactions - Oxfendazole or fenbendazole should not be given concurrently with the bromsalan flukicides (Dibromsalan, Tribromsalan). Abortions in cattle and death in sheep have been reported after using these compounds together.

 

Doses -

Horses:

For susceptible parasites:

a)   5 mg/kg PO; 10 mg/kg once daily for 5 days to treat S. vulgaris in foals. (Robinson 1987)

b)   5 mg/kg PO; 10 mg/kg for ascarids. (Roberson 1988b)

c)   For treatment of migrating large strongyles: 50 mg/kg PO for 3 consecutive days, or 10 mg/kg for 5 consecutive days. (Herd 1987)

 

Elephants:

For strongylosis:

a) 5 mg/kg po (Raman, et.al., 2000).

 

b) 2.5 mg/kg orally as a single dose (Chandrasekharan,2002);(Chandrasekharan et.al.,1995).

 

c) 2.0 –2.5 mg/kg orally as a single dose mixed with jaggery or rice (Chandrasekharan, 1992).

 

d) 5 mg/kg po in feed as a single dose (Strao et.al., 1992).

 

e) Chronic murshidiasis in an Asian elephant was resolved with 50 g fenbendazole repeated at 30 days (Tripathy et.al. 1991).

 

f) 5 mg/kg po as a single dose (Roy and Mazumdar, 1988).

 

g) 12 g of Panacur dissolved in 2000 ml water in 2 divided doses at a 3 -day interval (Lahkar and Das,1988).

 

Elephant References:
a) Raman,M., Jayathagaraj,M.G., Rajavelu,G., and John,M.C. 2000. Strongylosis in captive elephants - a report. Indian Journal of Animal Health 39:(2):85-86  Summary: Strongylosis was observed in a group of elephants (n=4) maintained in a private circus in Chennai, Tamil Nadu, India [date not given]. Examination of faecal samples showed larvae which were identified as Murshidia sp., Quilonia sp., and Decrusia sp. larvae. All elephants were treated with fenbendazole at a dose of 5 mg/kg body weight. A decline of egg count was observed after 1-2 days of treatment. Identification at the earlier stages of infection, good nutrition and hygiene, and less exertion might be the cause of absence of significant clinical signs like anaemia, dehydration and others. It is concluded that use of fenbendazole at the rate of 5 mg/kg body weight in the mega herbivores with repetition after 3 weeks, and regular deworming every 3-6 months, yield satisfactory results.

b) Chandrasekharan,K. 2002. Specific diseases of Asian elephants. Journal of Indian Veterinary Association Kerala 7:(3):31-34

b) Chandrasekharan,K., Radhakrishnan,K., Cheeran,J.V., Nair,K.N.M., and Prabhakaran,T., 1995. Review of the Incidence, Etiology and Control of Common Diseases of Asian Elephants with Special Reference to Kerala. In: Daniel,J.C. (Editor), A Week with Elephants; Proceedings of the International Seminar on Asian Elephants. Bombay Natural History Society; Oxford University Press, Bombay, India pp. 439-449

c) Chandrasekharan,K., 1992. Prevalence of infectious diseases in elephants in Kerala and their treatment. In: Silas,E.G., Nair,M.K., and Nirmalan,G. (Editors), The Asian Elephant: Ecology, Biology, Diseases, Conservation and Management (Proceedings of the National Symposium on the Asian Elephant held at the Kerala Agricultural University, Trichur, India, January 1989). Kerala Agricultural University, Trichur, India pp. 148-155

 

d) Rao, D.S.T., Yathiraj, S., Choudhuri, P.C., and Reddy, P.K. 1992. Treatment of helminthiosis in elephants. Indian Journal of Animal Science 62(12):1155-1156.
Ref ID: 2648 Abstract (Summary): Strongyle and paramphistome eggs were found in the faeces of 3 elephants belonging to S V Dairy Farm, Tirupati. The body weights of these elephants were calculated using the formula: weight (kg) = 12.8 (n+ng) - 4281, where g is chest girth (cm) and ng is neck girth (cm). A drug containing 25% fenbendazole was given orally at a dosage of 5 mg/kg. One elephant had diarrhoea and was also given astringent. No eggs were detected after 7 days in 2 cases and after 14 days in all 3 cases.

e) Tripathy,S.B., Acharjyo,L.N.M., and Padhi,N.K.  1991. Use of fenbendazole against murshidiasis in zoo elephant. International Seminar on Veterinary Medicine in Wild and Captive Animals, Nov. 8-10,
Bangalore, India. Pages: 29  Abstract: Treatment of a chronic case of murshidiasis in a captive elephant with fenbendazole has been reported.  Large numbers (epg 4200) of Murshidia eggs were detected in the faeces. Differential count of the blood revealed lymphocytosis (63%) and neutropenia (27%).  Reduction in feed intake, oedematous swelling on dependent parts of the body, debility and reduction in body weight were recorded. Oral administration of 50 g of Panacur (25% fenbendazole) repeated after 30 days, 50 g of Minamil (mineral mixture) once daily for 30 days and 100 g of Livol (liver tonic) daily for 15 days along with 30 ml of Neurobiocin IM every third day for 5 injections brought clinical recovery and gain in body weight 2 months and 4 months after initiation of treatment respectively.  The number of Murshidia eggs reduced by 70% and 100% in per gram of faeces when examined 5 and 10 days post treatment with anthelmintic, respectively.

         f)Roy,S. and Mazumdar,B.K. 1988. Anthelmintic activity of fenbendazole (Panacur) against Murshidia murshida in zoo elephants. Indian Veterinary Journal 65:(6):531-532 
Summary:  Three Indian elephants, Elephas maximus, infected with M. murshida were treated with a single dose of fenbendazole at 5 mg/kg mixed into feed (cooked rice). Faecal samples were negative in one elephant 3 days after treatment, and in all animals 7 days after treatment. No side effects were recorded.

         g) Lahkar,B.C. and Das,M.R. 1988. A note on the successful treatment of trichostrongyle infection of elephants (Elephas maximus) with Panacur (fenbendazole). Indian Veterinary Journal 65:(6):538  Summary:  Six Indian elephants, E. maximus infected with gastrointestinal nematodes (700-1400 epg faeces) were given 12 g Panacur (fenbendazole) in the form of a bolus with flour, in 2 doses 3 days part. Faecal samples from all animals were negative 3 days after the second dose. No side effects were recorded.         

Dosage Forms/Preparations/FDA Approval Status -

Veterinary-Approved Products:

Fenbendazole Granules 222 mg/gram (22.2%) in 0.18 oz & 1 g, 2 g, 4 g packets and 1 lb jars; Panacur®  Granules 22.2% (Hoechst). (Rx)  Approved for use in dogs.

 

Fenbendazole Granules 222 mg/gram (22.2%); Panacur® Granules 22.2% (Hoechst). (OTC)  Approved for use in horses not intended for food.

 

Fenbendazole Suspension 100 mg/ml (10%); available in both equine and bovine la­beled products; Panacur® Suspension  (Hoechst). (Rx)  Approved for use in horses (not intended for food) and cattle  Slaughter withdrawal=8 days (cattle). Safe-Guard® Suspension (Hoechst) (OTC)  Approved for use in beef and dairy cattle. Slaughter withdrawal = 8 days

 

Fenbendazole Paste 100 mg/gram (10%); available in both equine and bovine labeled products and sizes. Panacur® Paste  (Hoechst). (OTC)  Approved for use in horses (not intended for food) and cattle. Slaughter withdrawal=8 days (cattle). Safe Guard Paste® (Hoechst) (OTC) Approved for use in horses not intended for food and cattle. Slaughter withdrawal = 8 days; no milk withdrawal time.

 

Fenbendazole Medicated Block 750 mg/lb.; 25 lb. block; Safe-Guard Sweetlix® (Hoechst); (OTC)  Approved for use in beef cattle. Slaughter withdrawal= 16 days.

 

Fenbendazole Type B Medicated Feed

Safe-Guard EZ Scoop Swine Dewormer® (Hoechst) (OTC).  1.8% Fenbendazole No slaughter withdrawal time required

Safe-Guard 0.96% Scoop Dewormer® (Hoechst) (OTC) Approved for use in cattle. No milk withdrawal time; slaughter withdrawal time=13 days

 

Fenbendazole Type C Medicated Feed

Safe-Guard Free-choice Cattle Dewormer® (Hoechst) (OTC). 0.50% Fenbendazole (2.27 g/lb) Approved for use in beef and dairy cattle.  No milk withdrawal time.

Safe-Guard 35% Salt Free-choice Cattle Dewormer® (Hoechst) (OTC) 1.9 g/lb Fenbendazole. Approved for use in dairy and beef cattle. Slaughter withdrawal time=13 days;  no milk withdrawal time.

 

Fenbendazole Pellets

Safe-Guard 0.5% Cattle Top Dress® (Hoechst) (OTC)  Slaughter withdrawal time=13 days; no milk withdrawal period

Safe-Guard 1.96% Scoop Dewormer Mini Pellets® (Hoechst) (OTC)  Approved for use in beef and dairy cattle. No milk withdrawal time; slaughter withdrawal time=13 days

 

Fenbendazole Premix 20%  Type A (200 mg/gram)

Safe-Guard Premix® (Hoechst). (OTC)  Approved for use in swine. dairy and beef cattle, zoo & wildlife animals.  Slaughter withdrawal for cattle = 13 days; no milk withdrawal time. Slaughter withdrawal for swine=none. Wildlife animal slaughter (hunting) withdrawal = 14 days.

 

Human-Approved Products:  None

 

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