St John’s wort: Dosage. Adverse Reactions

Dosage Range

• Dried herb: 2-5 g/day.

• Liquid extract (1:2): 3-6 mL/day.

• Tincture (1:5): 7.5-1 5 mL/day.

• Standardised extract containing 1.0-2.7 mg total hypericin daily.

• It is advised that patients using St John’s wort long term should have their doses reduced slowly when discontinuing use.

EXTERNAL USE

• Oily macerate: macerate flowering tops in olive oil for several weeks and stir often, then drain through a gauze. Store in a dark bottle out of direct light. Apply oil directly to the affected area. To promote extraction of flavonoids, store in a sunny area for 6 weeks (oil will turn red).

ACCORDING TO CLINICAL STUDIES

(Doses are for dried herb or equivalent).

• Mild to moderate depression: adult — doses ranging from 350-1800 mg/day have been used; children (aged 6-12 years) — 200-400 mg/day in divided doses.

The extract most often studied is LI 160, although others have also been tested, such as WS 5573 (standardised to hyperforin), ZE 117 (a low concentration hyperforin preparation), WS 550 and STW3-V1.

• Major depression: 1800 mg/day in divided doses.

• OCD: 450 mg twice daily of an extract containing 0.3% hypericin.

• Menopausal symptoms: 900 mg/day in divided doses.

• PMS: 300 mg/day (standardised to 900 µg hypericin).

• SAD: 900 mg/day in divided doses.

Adverse Reactions

It has been estimated that approximately 1 in 30,000 people using St John’s wort will experience an adverse reaction, including those attributed to drug interactions. The incidence of side-effects to St John’s wort is approximately 10-fold lower than for conventional antidepressants (SSRIs). According to an overview of 16 post-marketing surveillance studies, gastrointestinal symptoms, sensitivity to light and other skin conditions and agitation were the most commonly reported side-effects and were generally described as mild.

PHOTOSENSITIVITY (UNLIKELYAT THERAPEUTIC DOSES)

The most common adverse event among spontaneous reports is photosensitivity, which is estimated to occur in 1 in 300,000 treated cases. This can occur with a dose of 5-10 mg/day hypericin, which is 2-4-fold higher than the recommended dose. Commission E has noted the possibility of photosensitivity reactions, particularly in fair-skinned people.