Title: Oxfendazole
CAS Registry Number: 53716-50-0
CAS Name: [5-(Phenylsulfinyl)-1H-benzimidazol-2-yl]carbamic acid methyl ester
Additional Names: methyl-5-(phenylsulfinyl)-2-benzimidazolecarbamate; 5-phenylsulfinyl-2-carbomethoxyaminobenzimidazole
Manufacturers' Codes: RS-8858
Trademarks: Autoworm (Schering-Plough); Benzelmin (Fort Dodge); Synanthic (Fort Dodge); Systamex (Schering-Plough)
Molecular Formula: C15H13N3O3S
Molecular Weight: 315.35
Percent Composition: C 57.13%, H 4.16%, N 13.32%, O 15.22%, S 10.17%
Literature References: Prepn: C. Beard et al., DE 2363351; eidem, US 3929821 (1974, 1975, both to Syntex); E. A. Averkin et al., J. Med. Chem. 18, 1164 (1975). Metabolism: J. P. Bell, R. V. Tomlinson, Fed. Proc. 35, 487 (1976). Radioimmunoassay: C. Nerenberg et al., J. Pharm. Sci. 67, 1553 (1978). Efficacy evaluations: J. L. Duncan, J. G. Reid, Vet. Rec. 103, 332 (1978); N. F. Baker et al., Am. J. Vet. Res. 39, 1258 (1978).
Properties: Crystals from chloroform-methanol, mp 253° (dec). LD50 in dogs, rats, mice: >1600, >6400, >6400 mg/kg (Averkin).
Melting point: mp 253° (dec)
Toxicity data: LD50 in dogs, rats, mice: >1600, >6400, >6400 mg/kg (Averkin)
Therap-Cat-Vet: Anthelmintic.
Oxibendazole Oxiconazole Nitrate Oxidimethiin Oxidized Cellulose Oxidronic Acid

Systematic (IUPAC) name
Methyl N-[6-(benzenesulfinyl)-1H-1,3-benzodiazol-2-yl]carbamate
Clinical data
AHFS/Drugs.com International Drug Names
Legal status  ?
CAS number 53716-50-0
ATCvet code QP52AC02
PubChem CID 40854
ChemSpider 37316
Chemical data
Formula C15H13N3O3S 
Mol. mass 315.3 g/mol

Oxfendazole is the sulfoxide form of fenbendazole, a broad spectrum benzimidazole anthelmintic. Its main use is for protecting livestock against roundworm, strongyles and pinworms.[1]

Oxfendazole is an anthelmintic (wormer) compound used in veterinary practice. It comes under the chemical class of the benzimidazoles. This drug is barely used in horses, goats, sheep, and cattle. It is very scarcely applied on dogs and cats. The drug for livestock is majorly available in the form of pills, tablets, drenches, bolus, etc. They are meant for oral consumption. Several drenches are allowed for intraruminal injection in some of the countries. Few countries also prefer injectables and pour-ons. For pet dogs, the drug is available in the form of drenches.


Oxfendazole is fenbendazole sulfoxide’s main metabolite. They are highly effective. They are efficient against gastrointestinal lungworms and roundworms of livestock, adults, and L4-larvae of the significant species for example, of the genus of Bunostomum, Haemonchus, Ostertagia - Oesophagostomum, Nematodirus, Teladorsagia, Cooperia, Trichostrongylus, Dictyocaulus, Trichuris, etc, including against arrested larvae of some of the species. They are even highly efficient against majority of the livestock tapeworms. This drug works effectively against the main parasitic roundworms and tapeworms of dogs and cats.

The drug offers a small residual effect in ruminants unless and otherwise it is delivered by using a slow-release device. This essentially means that on a single administration it will help in killing the parasites which are present in the host during the time of treatment and also prevent against re-infestations for some more days but not weeks or months. The residual effect is comparatively shorter in non-ruminants. The drug is non-effective against flukes and external parasites at therapeutic dose.