Purpose: The purpose of this study was to compare the bioavailability between 2 milk thistle-containing dietary supplements, Product B and IsaGenesis, in healthy volunteers.
Methods: Bioavailability between Product B, originally formulated as a powdered capsule, and IsaGenesis, reformulated as a soft gel, were compared by measuring silybin A and silybin B as surrogate pharmacokinetic markers for differences in absorption and bioavailability. For this randomized, open-label, crossover pharmacokinetic study, 12 healthy volunteers consumed a single-dose serving of each supplement separated by at least a 7-day washout period. Serial blood samples were obtained at 0, 0.5, 1, 1.5, 2, 3, 4, 6, and 8 hours and analyzed via LC-MS/MS.
Findings: Rapid absorption and elimination of silybin A and silybin B have been observed after oral administration of both Product B and IsaGenesis. However, the absorption rate and extent, as indicated by mean the Cmax and mean plasma AUC, were significantly higher for the IsaGenesis soft gel formulation. The dose-corrected mean Cmax was 365% and 450% greater for silybin A and B, respectively, relative to powdered Product B. The time to Tmax was reached, on average, at least 1 hour earlier with IsaGenesis relative to Product B for both silybin A and silybin B.
Implications: The IsaGenesis soft gel formulation provided substantially greater absorption and bioavailability of silybin A and silybin B relative to the powdered Product B supplement. ClinicalTrials.gov Identifier: NCT02529605.
Keywords: absorption; formulation; milk thistle; pharmacokinetic properties; silybin.
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