Several studies show that St John's wort can treat depression as effectively as the more expensive prescription drugs. It is felt to be so safe that you can buy it without a prescription. However, an editorial in the British medical journal, Lancet, cautions that St. John's wort can combine with other drugs to harm you.

The active ingredients in St. John's wort are broken down by the same cytochrome P450 enzyme in the liver that breaks down many other drugs. For example, St John's wort can lower blood level of theophylline and bring on an asthma attack, it may block birth control pills and cause pregnancy, it may block estrogen replacement in postmenopausal women and cause uterine bleeding, it can lower blood levels of digitalis to worsen heart failure and it may block coumadin to cause clotting. The editorial in the Lancet recommends that if you use any other drugs, check with your doctor to see if there is any interaction between St. John's wort and your medication.

Lancet December 11, 1999; 354:214-5.

Checked 8/9/05

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