Objective—To determine the oral bioavailability, single and multidose pharmacokinetics, and safety of silibinin, a milk thistle derivative, in healthy horses.
Animals—9 healthy horses.
Procedures—Horses were initially administered silibinin IV and silibinin phospholipid orally in feed and via nasogastric tube. Five horses then consumed increasing orally administered doses of silibinin phospholipid during 4 nonconsecutive weeks (0 mg/kg, 6.5 mg/kg, 13 mg/kg, and 26 mg/kg of body weight, twice daily for 7 days each week).
Results—Bioavailability of orally administered silibinin phospholipid was 0.6% PO in feed and 2.9% via nasogastric tube. During the multidose phase, silibinin had nonlinear pharmacokinetics. Despite this, silibinin did not accumulate when given twice daily for 7 days at the evaluated doses. Dose-limiting toxicosis was not observed.
Conclusions and Clinical Relevance—Silibinin phospholipid was safe, although poorly bio-available, in horses. Further study is indicated in horses with hepatic disease.
Objective—To evaluate antioxidant capacity and inflammatory cytokine gene expression in horses fed silibinin complexed with phospholipid.
Animals—5 healthy horses.
Procedures—Horses consumed increasing orally administered doses of silibinin phospholipid during 4 nonconsecutive weeks (0 mg/kg, 6.5 mg/kg, 13 mg/kg, and 26 mg/kg of body weight, twice daily for 7 days each week). Dose-related changes in plasma antioxidant capacity, peripheral blood cell glutathione concentration and antioxidant enzyme activities, and blood cytokine gene expression were evaluated.
Results—Plasma antioxidant capacity increased throughout the study period with increasing dose. Red blood cell nicotinamide adenine dinucleotide phosphate:quinone oxidoreductase I activity decreased significantly with increasing doses of silibinin phospholipid. No significant differences were identified in glutathione peroxidase activity, reduced glutathione or oxidized glutathione concentrations, or expression of tumor necrosis factor α, interleukin-1, or interleukin-2.
Conclusions and Clinical Relevance—Minor alterations in antioxidant capacity of healthy horses that consumed silibinin phospholipid occurred and suggest that further study in horses with liver disease is indicated.