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Pharmacological particulars
Pharmacotherapeutic group: Anthelmintic. ATC vet code: QP52AA51
Pharmacodynamic properties
This product contains anthelmintics active against gastrointestinal roundworms and tapeworms. The product contains three active substances, as follows: Febantel, a probenzimidazole, Pyrantel embonate (pamoate), a tetrahydropyrimidine derivative, Praziquantel, a partially hydrogenated pyrazinoisoquinoline derivative. In this fixed combination, pyrantel and febantel act against all relevant nematodes (ascarids, hookworms, and whipworms) in dogs. In particular, the activity spectrum covers Toxocara canis, Toxascaris leonina, Uncinaria stenocephala, Ancylostoma caninum and Trichuris vulpis. This combination shows synergistic activity in the case of hookworms and febantel is effective against T. vulpis. The spectrum of activity of praziquantel covers all important cestode species in dogs, in particular Taenia spp., Dipylidium caninum, Echinococcus granulosus and Echinococcus multilocularis. Praziquantel acts against all adult and immature forms of these parasites. Praziquantel is very rapidly absorbed through the parasite’s surface and distributed throughout the parasite. Both in vitro and in vivo studies have shown that praziquantel causes severe damage to the parasite integument, resulting in the contraction and paralysis of the parasites. There is an almost instantaneous tetanic contraction of the parasite musculature and a rapid vacuolization of the syncytial tegument. This rapid contraction has been explained by changes in divalent cation fluxes, especially calcium. Pyrantel acts as a cholinergic agonist. Its mode of action is to stimulate nicotinic cholinergic receptors of the parasite, induce spastic paralysis of the nematodes and thereby allow removal from the gastrointestinal system by peristalsis. Within the mammalian system, febantel undergoes ring closure, forming fenbendazole and oxfendazole. It is these chemical entities which exert the anthelmintic effect by inhibition of tubulin polymerisation. Formation of microtubules is thereby prevented, resulting in disruption of structures vital to the normal functioning of the helminth. Glucose uptake in particular is affected, leading to a depletion in cell ATP. The parasite dies upon exhaustion of its energy reserves, which occurs 2–3 days later.
Pharmacokinetic particulars
Orally administered praziquantel is absorbed almost completely from the intestinal tract. After absorption, the drug is distributed to all organs. Praziquantel is metabolized into inactive forms in the liver and secreted in bile. It is excreted within 24 hours to more than 95% of the administered dosage. Only traces of non-metabolised praziquantel are excreted. Following administration of the product to dogs, peak plasma concentrations of praziquantel were achieved by approximately 2.5 hours. The pamoate salt of pyrantel has low aqueous solubility, an attribute that reduces absorption from the gut and allows the drug to reach and be effective against parasites in the large intestine. Following absorption, pyrantel pamoate is quickly and almost completely metabolized into inactive metabolites that are excreted rapidly in the urine. Febantel is absorbed relatively rapidly and metabolized to a number of metabolites including fenbendazole and oxfendazole, which have anthelmintic activity. Following administration of the product to dogs, peak plasma concentrations of fenbendazole and oxfendazole were achieved by approximately 7–9 hours.