St. John's Wort Fact Sheet

Medication Name (brand):

St. John's Wort

Medication Name (clinical):

St. John's Wort

Indications:

Not regulated by the FDA, considered a dietary supplement.

Mechanism:

Mechanism of psychiatric effect is unclear. Active antidepressant ingredients likely
are hypericin and/or hyperforin. Both may inhibit the reuptake of serotonin, norepinephrine, and
dopamine, but other neurochemical effects have been suggested as well.

Dosing:

Usual dose is 300 mg TID.
• The standard preparation used to be 0.3% hypericin, but now manufacturers are offering
products standardized to 2% to 6% hyperforin, since many believe hyperforin is the most
important antidepressant component.

Cost:

Assuming 900 mg QD, the cost is usually in the range of 50 cents to $1 per day.

Evidence of Efficacy:

Major Depression: About 30 randomized, double blind controlled trials have shown
antidepressant efficacy, but most of these were published in European journals. U.S. trials
have been mixed.

What Is It?:

St. John’s Wort is a flowering herb (Hypericum perforatum) that blooms around
June 24 (St. John’s Day).

Side Effects:

Rate of side effects similar to placebo and lower than standard antidepressants in
controlled trials. Mild GI side effects and sedation are possible. Photosensitivity in fairskinned
people. Switch to mania has been reported. No sexual side effects.

Drug-drug Interactions:

Probably induces the 3A4 isoenzyme of the P450 family of hepatic enzymes.
• May decrease levels of the following drugs: cyclosporin (an immunosuppressive),
indinavir (a protease inhibitor), warfarin, theophylline, digoxin, and oral contraceptives.
• May cause serotonin syndrome in combination with SSRIs, but this is rare.
• Little information is available on interaction with MAOIs, but most authorities
recommend avoiding this combination.

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