Plasma disposition and faecal excretion of oxfendazole, fenbendazole and albendazole following oral administration to donkeys.

The research article investigates the metabolic cycle and excretory patterns of three de-worming agents—Fenbendazole, oxfendazole, and albendazole—in donkeys. After administering the drugs, faecal and plasma samples were analyzed to determine how these medicines metabolize and exit the body. The study reveals that oxfendazole had a higher plasma presence compared to the other two, and that donkeys have lower bioavailability and efficiency with these medications when compared to ruminants.

Study Methodology

• The three de-worming agents Fenbendazole (FBZ), Oxfendazole (FBZSO), and Albendazole (ABZ) were administered to donkeys at a dosage of 10mg/kg body weight.
• Post administration, both blood and faecal samples were taken at periodic intervals from 1 to 120 hours.
• These samples underwent analysis with high-performance liquid chromatography (HPLC) to scrutinize the presence and changes in these de-worming agents and their metabolites.

Plasma Disposition

• Fenbendazole (FBZ) and its metabolites were absent in all blood samples after its administration, which suggests it was not absorbable into the bloodstream.
• Although Albendazole (ABZ) was not detected in the plasma, its metabolites were, indicating that ABZ moves through, and is fully metabolized by, first-pass mechanisms in donkeys.
• After administering FBZSO, top concentrations of FBZSO and FBZSO(2) were found around 5.67 and 8.00 hours respectively.
• Following administration of ABZ, peak levels of the sulphoxide metabolite and sulphone metabolite were noted at approximately 5.71 and 8.00 hours respectively.
• The research points out that there were significantly higher concentrations of these drug’s metabolites than the initial administered drugs.

Faecal Excretion

• The highest dry-faecal concentrations of the administered molecules occurred near the 30-hour mark for all three drugs.
• Following delivery of FBZSO, the sulphide metabolite was significantly higher compared to the parent molecule.
• As per the faecal samples, the parent molecule remained dominant after administering FBZ.
• After administering ABZ, the parent molecule considerably metabolized through the GI microflora to its sulphoxide metabolite.
• The area under the curve, a measure of total drug exposure, for the parent FBZ was higher compared to that for FBZSO and ABZ in faeces.

Conclusions

• The research concluded that the plasma concentration of FBZSO was substantially higher than that of FBZ and ABZ.
• Although ABZ is not licensed for use in equine animals, its metabolites showed a better plasma kinetic profile compared to FBZ, which is permissible for use in horses.
• The study also revealed that due to high metabolic activity, first-pass effects, and lower absorption of these drugs, donkeys experience decreased bioavailability and efficiency when compared to ruminants.