Chemistry - A phenylguanidine anthelmintic, febantel occurs as a colorless powder. It is insoluble in water and alcohol. Structurally, febantel is related to the benzimidazoles. As febantel is at least partially metabolized to fenbendazole and oxibendazole in vivo, it is sometimes categorized as a probenzimidazole agent.
Storage/Stability/Compatibility - Febantel (alone) should be stored at room temperature.
Partially used febantel (Rintal®) syringes may be stored for up to one year if capped tightly and expiration date is not exceeded. When mixed extemporaneously with trichlorfon (Combot®), it should be stored tightly sealed and used within 6 days if kept at room temperature and within 2 months if refrigerated. Mix well before administering.
Pharmacology - The mode of action of this agent is thought to be via inhibition of fumarate reductase in the worm, thereby blocking glucose uptake. The majority of the activity is believed to be derived from the active metabolites, fenbendazole and oxfendazole.
Uses/Indications - Febantel paste and oral (tube) suspension is indicated (labeled) for the treatment of large and small strongyles (Strongulus vulgaris, S. edentatus, S. equinus), ascarids (P. equorum—adult and sexually immature forms), and pinworms (Oxyuris equi—adult and 4th stage larva) in horses. In combination with trichlorfon (Combotel®), it is indicated (labeled) for the removal of the mouth and stomach stages of bots (Gastrophilus intestinalis, G. nasalis).
Febantel (in combination with praziquantel—Vercom®) is indicated (labeled) for the following intestinal parasites in dogs and puppies: hookworms (Ancylostoma caninum), roundworms (Toxocara canis), whipworms (Trichuris vulpus) and tapeworms (Dipylidium caninum & Taenia pisiformis).
Febantel (in combination with praziquantel—Vercom®) is indicated (labeled) for the following intestinal parasites in cats and kittens: hookworms (Ancylostoma tubaeforme), roundworms (Toxocara canti) and tapeworms (Dipylidium caninum & Taenia taeniaeformis).
Although not approved for use in cattle or sheep, febantel has greater than 85% efficacy against the following helminths in those species: Abomasal nematodes, small intestinal nematodes, large intestinal nematodes (Oesophogostomum spp.), lungworms and trematodes (F. hepatica— 4 week to 15 week stages; not in sheep).
Pharmacokinetics - In the horse, febantel is apparently readily absorbed from the GI tract and is rapidly metabolized to fenbendazole-sulphone, fenbendazole and oxibendazole. Febantel is also absorbed from the intestine in cattle and sheep. Sheep apparently absorb and metabolize the drug faster than do cattle. Maximum plasma concentrations occur 6-12 hours after dosing in sheep and 12-24 hours in cattle.
Contraindications/Precautions - When used alone in horses, the manufacturer lists no contraindications to the use of the drug. It is considered to be safe in breeding stallions and pregnant mares. The combination product (Combotel®) is labeled as being contraindicated in horses “...suffering from colic, diarrhea, constipation, or infectious disease until such conditions have been corrected.” The combination product (Vercom®) is contraindicated in pregnant small animals.
Adverse Effects/Warnings - When used at recommended dosages in horses, adverse reactions are unlikely to occur. Anaphylaxis is listed as a possible reaction, but case reports documenting this were not found in the literature. At very high doses (8 times labeled), a self-limiting diarrhea has been described.
Adverse effects in horses with the combination product Combotel®, include mouth irritation with resultant salivation, occasional diarrhea and colic. Adverse effects are more likely to occur if given on an empty stomach or if feed is withheld prior to dosing.
In dogs and cats, Vercom® (febantel & praziquantel) is unlikely to cause serious adverse effects at usual doses. Dogs may exhibit salivation, anorexia, emesis or gagging, and diarrhea or soft stools. Incidence of these effects was less than 3% of dogs treated in clinical trials. Cats may show signs (less than 10% incidence) of salivation, vomiting, depression and rejection of the paste. These effects are described as mild and self-limiting.
Overdosage/Toxicity - In horses, febantel has a reported 40X margin of safety after a single oral dose. Slightly decreased red blood cell counts, hemoglobin and hematocrit may be noted for 3 weeks after this dosage. Repeated doses of 8X recommended resulted only in a self-limiting diarrhea.
While, in horses there is a considerable safety factor for febantel, there is much less so for trichlorfon (in Combotel®). For more information on the toxicity for this compound (trichlorfon) refer to its monograph found later in this section.
The LD50 in dogs is greater than 10 g/kg of febantel. When administered at 15X recommended dose to mature dogs and cats, or 10X recommended dose to puppies or kittens for 6 days, transient salivation, diarrhea, vomiting and anorexia were noted. In dogs receiving 5 or 10 mg/kg PO for 90 days, testicular and prostatic hypoplasia were noted.
Drug Interactions, Drug/Laboratory Interactions - None reported.
For labeled indications:
a) 6 mg/kg PO or tube; retreat in 6-8 weeks if reinfection is likely to occur. (Robinson 1987), (Package Inserts; Rintal® Paste & Suspension—Miles)
Monitoring Parameters -1) Efficacy; 2) Adverse effects, if severe
Client Information - Clients should be informed on general measures to reduce exposure to helminth eggs and larva. Dogs with concomitant flea and Dipylidium caninum infestations should have measures taken to remove the fleas from the animal and the environment.
Dosage Forms/Preparations/FDA Approval Status -
Febantel Oral Paste 45.5%; 6 gram, and 36 gram (multi-dose) syringe
Rintal® Paste (Bayer), (OTC) Approved for use in horses.
Febantel Suspension 93 mg/ml (9.3%) in 26 fl. oz. bottles
Rintal ® Suspension (Bayer); (Rx) Approved for use in horses.
Febantel 3.4% (34 mg/gram) and Praziquantel 0.34% (3.4 mg/gram) Oral paste syringe; 4.8 g, 12 g, and 36 g syringes
Vercom® Paste (Bayer); (Rx) Approved for use in dogs, cats, puppies, and kittens.
Praziquantel/pyrantel pamoate plus febantel; Drontal Plus Tablets® (Bayer) (Rx) small, medium and large dog sizes
May also be known as Amatron® or Bayverm® in the U.K..
Human-Approved Products: None
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