Drug interactions with St. John's Wort (Hypericum perforatum): a review of the clinical evidence.
Level 5 - mechanism / opinion, no new human data
Narrative review without systematic methodology
PubMed 15049433 · doi:10.5414/cpp42139
What was done
A narrative review of clinical evidence and reports assessing pharmacokinetic and pharmacodynamic interactions between St. John's Wort (Hypericum perforatum) and prescribed medications. The abstract does not report search databases, date ranges, or study selection criteria.
What was found
The abstract reports no numerical values or effect sizes. It reports that St. John's Wort lowers plasma concentrations or pharmacological effects of alprazolam, amitriptyline, cyclosporine, digoxin, fexofenadine, indinavir, irinotecan, methadone, nevirapine, simvastatin, tacrolimus, theophylline, warfarin, phenprocoumon, and oral contraceptives. These pharmacokinetic interactions are attributed to the induction of P-glycoprotein and cytochrome P450 enzymes, particularly CYP 3A4. Concomitant use with buspirone or serotonin reuptake inhibitor antidepressants (such as sertraline, paroxetine, and nefazodone) can cause serotonin syndrome.
Why it matters
St. John's Wort has a high potential for clinically significant interactions with widely used pharmaceuticals, including narrow therapeutic index drugs and psychiatric medications.
Limits
The abstract describes a narrative review rather than a systematic review and does not provide sample sizes, study counts, quantitative pharmacokinetics, or data on extract standardization and dosing.
Cited by
- supports Combining St. John's wort with an SSRI medication can adversely interfere with serotonin levels.