St. John's Wort is a popular herbal product many people use to treat minor to moderate depression. Yet if they are additionally taking other drug medications they may be causing greater problems and/or symptoms for themselves.

A recent study conducted by the Medical University of South Carolina in Charleston, found that St. John's Wort can change the way certain medications are used by the body and that this may have dangerous drug interactions.

This study supports that herbal medicines are powerful substances that have direct biochemical effects on the body and should not be used in conjunction with other medications due to possible interactions or side-effects.

It is always best to consult a qualified practitioner before using any new remedies if you are currently taking over the counter or prescription medicine.

The study, found that over a 14-day course of using St John's Wort, the effectiveness of certain medications would be decreased, requiring increased dosage requirements to remain effective. St Johns Wort has this effect because it changes the chemical pathway that is used by 50% of marketed medications. The study has been published in theJournal of American Medical Association.

The study
From March 2002 to February 2003, 12 healthy subjects (six men and six women) aged 22 to 38 years received probe drugs (30 mg of dextromethorphan and 2 mg of alprazolam) to establish baseline CYP 2D6 and CYP 3A4 activity. After a minimum washout period of seven days, subjects received one 300-mg tablet of St. John's wort three times daily for 14 days. They then received the probe drugs along with one St. John's wort tablet to determine postadministration CYP activity, and they continued on the St. John's wort dosing regimen for 48 hours.

Following St. John's wort administration, alprazolam elimination half-life decreased from 12.4 hours to 6.0 hours. Seven of 12 subjects had measurable alprazolam concentrations 36 hours after dosing while receiving St. John's wort compared with all 12 subjects at baseline. No subjects had measurable alprazolam concentrations 48 hours after dosing while receiving St. John's wort, compared with 11 of 12 subjects during the baseline phase.

The results
The results indicate that long-term, chronic use of St. John's wort may cause diminished clinical effectiveness or increased dosage requirements for all CYP 3A4 substrates.
About half of marketed medications use this cytochrome pathway.
The findings underscore the potential inherent problems associated with the widespread practice of using herbal products at the same time with conventional medications.

Reference:Effect of St John's Wort on Drug Metabolism by Induction of Cytochrome P450 3A4 Enzyme John S. Markowitz; Jennifer L. Donovan; C. Lindsay DeVane; Robin M. Taylor; Ying Ruan; Jun-Sheng Wang; Kenneth D. Chavin JAMA. 2003;290:1500-1504.

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