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St. John's Wort
Bits & Pieces
by Erowid

The "Bits & Pieces" section is intended for random snippets of information which don't fit
easily elsewhere and/or which have been newly added, but not yet carefully categorized.

  • St. John's Wort Extract Increases CYP3A Enzyme Activity
    Although there are some contradictory descriptions, some saying that it inhibits this enzyme, St. John's Wort appears to increase metabolic activity of CYP3A enzymes. See Whitten DL, Myers SP, et al 2006. A number of papers describing in vitro and in vivo research have been published and there are several review papers looking at these. One paper concludes "This suggests that long-term administration of St John's wort may result in diminished clinical effectiveness or increased dosage requirements for all CYP 3A4 substrates, which represent at least 50% of all marketed medications." (Markowitz, Donovan, et al. 2003)

  • St. John's Wort Extract Decreases Duration of Alprazolam's Effects
    One well documented effect of St. John's Wort extracts is to decrease the duration of alprazolam (and probably other benzodiazepines). In one study, the elimination half life was cut in half, from an average of 12 hours to an average of 6 hours, after giving St. John's Wort for 14 days prior to the test. See Markowitz, Donovan, et al. 2003.

  • Different Product Formulations Have Very Different Active Levels
    Research into St. John's Wort find that different products and brands have very different levels of effectiveness at treating depression. It is unclear exactly what difference between products leads to this difference in effectiveness since most of this research has not tested levels of active chemicals contained in the products. Induction (increased activity) of CYP3A enzymes has also been found to differ between products.