Bioavailability of Goldenseal

Goldenseal has poor oral bioavailability with approximately 40% absorption, which is further reduced by approximately 50% when taken with food. 1

Pharmacokinetics of Goldenseal

Goldenseal (Hydrastis canadensis L.) contains several bioactive alkaloids, with berberine and hydrastine being the primary constituents, along with palmatine, canadine, and hydrastinine in smaller amounts 2, 3
When taken orally, goldenseal has limited bioavailability, similar to other herbal supplements with complex alkaloid compositions 1
Absorption occurs in the gastrointestinal tract with a double-peaked curve for intestinal absorption, suggesting a complex uptake mechanism 1
Taking goldenseal with meals significantly decreases its bioavailability by approximately 50% compared to taking it on an empty stomach 1
Total bioavailability is estimated to be between 40-70%, with considerable interindividual variation 1
Once absorbed, approximately 80% of goldenseal alkaloids circulate bound to plasma proteins 1

Goldenseal is primarily metabolized through the liver via the cytochrome P450 enzyme system, particularly CYP3A4 and CYP2D6 1
This extensive hepatic metabolism contributes to its variable bioavailability and potential for numerous drug interactions 1
The majority of goldenseal and its metabolites (>80%) are excreted via the kidneys 1
The excretion half-life ranges from 1.7-7 hours, though metabolites can be detected in urine for months after discontinuation 1

The limited and variable bioavailability of goldenseal contributes to unpredictable clinical effects 1
Goldenseal has high potential for drug interactions due to its metabolism through the CYP3A4 and CYP2D6 systems 1
Guidelines recommend holding goldenseal supplements for at least 2 weeks before surgical procedures due to these potential interactions 1
Berberine, the major alkaloid in goldenseal, has been shown to have antimicrobial, anti-inflammatory, and other therapeutic effects, but its clinical efficacy is limited by poor absorption 2

Despite limited bioavailability, goldenseal and its alkaloids can accumulate in tissues due to their lipophilic nature 1
Berberine and palmatine, two major alkaloids in goldenseal, have demonstrated phototoxic effects in human cells 4
Long-term exposure to goldenseal has been associated with potential hepatotoxicity in animal studies 5
The National Toxicology Program found evidence of carcinogenic activity in rats and mice exposed to goldenseal root powder over 2 years, possibly related to DNA damage from berberine inhibiting topoisomerase II 5, 6

Parenteral administration may improve bioavailability compared to oral dosing, as seen with similar compounds 1
Taking goldenseal on an empty stomach rather than with meals can significantly improve absorption 1
Formulation improvements, similar to those developed for cyclosporine (changing from simple solution to microemulsion), might enhance goldenseal bioavailability but have not been well-studied 1