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St. John's Wort (Hypericum)

Forms of St. John's Wort

St. John's Wort extract is a natural supplement that is sold by a variety of manufacturers. It is available in tablet and capsule form, which are usually standardized to contain 0.3% Hypericin, one of the active compounds. It is also available as a liquid extract (tincture).

The actual plant (Hypericum perforatum) can also be consumed as a tea made from the dried tops and flowers.

Other names for this plant include Johnswort, Amber, Touch-and-heal, Goat weed, Hardhay, Klamath Weed, Rosin Rose, Hypericum, and Tipton weed.

Uses of St. John's Wort

In psychiatry, St. John's Wort can be used for Depressive Disorders and Anxiety Disorders.

In general medicine, St. John's Wort may also be help in wound healing by decreasing inflammation and preventing infection.

How St. John's Wort Works

St. John's wort (Hypericum perforatum) is a plant with yellow flowers. It contains many chemical compounds. The ones that are thought to be important for its medicinal properties are Hypericin and Hyperforin. The way that these compounds work is not yet fully understood, but preliminary studies suggest that may increase serotonin activity by preventing serotonin reuptake in the central nervous system.

Cautions when Using St. John's Wort

St. John's Wort could in theory induce Manic or Mixed Episodes and Rapid Cycling in people with Bipolar Disorder.

St. John's Wort should not be used during or within 14 days following the administration of an MAOI, because a hypertensive crisis may result.

People with HIV/AIDS who are taking protease inhibitors or non-nucleoside reverse transcriptase inhibitors should avoid taking St. John's Wort.

St. John's Wort may interfere with the effectiveness of oral contraceptives.

Dosing of St. John's Wort

The recommended dose of the capsule or tablet is 300mg taken three times per day, usually with meals. It is suggested to wait about 4 weeks at this dose for therapeutic effects to appear before deciding to increasing the dose further to 600mg three times per day.

When wanting to stop this medication, the dose should probably be decreased gradually over a period of a few weeks.

Onset of action

Therapeutic effects are not expected before 2-4 weeks at a dose of 900mg/day. If no significant effects are seen after 6-8 weeks of use, including at least 2 weeks at a dose above 900mg/day, then the medication may not work at all.

Side-effects of St. John's Wort

The most common side-effects of St. John's Wort include dry mouth, dizziness, diarrhea, nausea, increased sensitivity to sunlight, fatigue, restlessness, anxiety, and sexual dysfunction (including impotence). Overall, the rates of side-effects caused by St John's Wart are low, not much greater than a placebo pill, and less than most standard antidepressants.

St. John's Wort and pregnancy

Some animal studies show adverse effects at high doses, but no controlled human studies have been done; should only be used in pregnancy if clearly needed and if benefits outweigh potential risks. For further information, see the section on treating Depression in pregnancy.

Medical Monitoring for St. John's Wort

None for healthy individuals.

Drug Interactions with St. John's Wort

  • Caution should be used when combining St. John's Wort with other medications that can increase bleeding time and reduce blood clotting, including Aspirin, NSAIDs, anti-platelet agents, Heparin and Coumadin.
  • Use caution when combining St. John's Wort with other serotonergic medications, including antidepressants and triptans, as this could potentially precipitate a serotonin syndrome.
  • St. John's Wort should not be used during or within 14 days following the administration of an MAOI, because a hypertensive crisis may result.
  • St. John's Wort can interfere with the metabolism of Carbamazepine, Cimetidine, Cyclosporin, Dextromethorphan, Fexofenadine, Imatinib, Irinotecan, Midazolam, Nifedipine, Omeprazole, Simvastatin, Theophylline, Tolbutamide, Warfarin, HIV drugs such as non-nucleoside reverse transcriptase inhibitors or protease inhibitors, and chemeotherapy drugs such as anathracyclines.
  • St. John's Wort may interfere with the effectiveness of oral contraceptives.