A St. John’s wort experiment found that extract composition affected a measured diazepam interaction.
Researchers compared ethanolic and aqueous Hypericum extracts, an infusion, tablets, and capsules in mice. Outcomes included diazepam-related motor coordination impairment, pentobarbital sleeping time, and paracetamol pharmacokinetics. The ethanolic extract had the highest measured hypericin and pseudohypericin concentrations and most strongly potentiated the diazepam motor effect.
The paper therefore concerns specific preparations and acute pretreatment. It does not justify treating every St. John’s wort product as pharmacologically identical.
A mouse rotarod result is not a human driving study. Nor can an acute experiment settle the effects of chronic use, where metabolic adaptation may differ. The diazepam outcome was pharmacodynamic; the paracetamol measurements should not be substituted for diazepam blood concentrations.
In an exposure review, record the supplement formulation, timing, and duration alongside the prescribed medicine. “Herbal product use” alone is too imprecise to reproduce this experiment or quantify an individual interaction. The study supports asking about co-exposures while retaining uncertainty about their human magnitude.
Original analysis of the supplied journal article, identified as PMC6272045.