title: Interaction of St John's wort with conventional drugs: systematic review of clinical trials.
abstract: OBJECTIVE
  To determine the methodological quality of clinical trials that examined possible interactions of St John's wort with conventional drugs, and to examine the results of these trials.
  
  
  METHODS
  Systematic review.
  
  
  METHODS
  Electronic databases from inception to April 2004, reference lists from published reports, and experts in the field.
  
  
  METHODS
  Eligible studies were prospective clinical trials evaluating the pharmacokinetic effect of St John's wort on the metabolism of conventional drugs.
  
  
  METHODS
  Two reviewers selected studies for inclusion and independently extracted data.
  
  
  RESULTS
  22 pharmacokinetic trials studied an average of 12 (SD 5) participants; 17 trials studied healthy volunteers and five studied patients. Most (17) studies used a "before and after" design; four studies used control groups other than the active group. Three studies randomised the sequence of administration or the participants to study arms or periods; three studies blinded participants or investigators. In 15 trials, investigators independently assayed the herb. Of 19 trials with available plasma data, three found no important interaction (change in area under the curve < 20%) and 17 found a decrease in systemic bioavailability of the conventional drug; in seven studies the 95% confidence interval excluded a decrease of < 20%.
  
  
  CONCLUSIONS
  Clinicians and patients should beware of possible decreases in the systemic bioavailability of conventional drugs when taken concomitantly with St John's wort.
authors.affiliation: Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, ON, Canada L8N 3Z5. millsej@mcmaster.ca
authors.forename: Edward
authors.initials: E
authors.lastname: Mills
authors.forename: Victor M
authors.initials: VM
authors.lastname: Montori
authors.forename: Ping
authors.initials: P
authors.lastname: Wu
authors.forename: Keith
authors.initials: K
authors.lastname: Gallicano
authors.forename: Mike
authors.initials: M
authors.lastname: Clarke
authors.forename: Gordon
authors.initials: G
authors.lastname: Guyatt
mesh_terms: D019540:Area Under Curve; D002986:Clinical Trials as Topic / Q000592:standards; D041743:Herb-Drug Interactions; D006801:Humans; D020902:Hypericum / Q000378:metabolism*; D015588:Observer Variation; D010599:Pharmacokinetics