Page 28 - phytotherapy_ EBOOK_2025

Actions and Uses
St. John’s wort has a long history of use in traditional medicine, particularly for treating
wounds. Its antibacterial activity was first validated by scientific studies published in 1959
and later in 1971.
The herb’s popularity increased dramatically when it became widely available as an over-
the-counter remedy for mild to moderate depression. However, subsequent reports raised
significant safety concerns. One study demonstrated that St. John’s wort reduced plasma
levels of the protease inhibitor indinavir, while another linked its use to heart transplant
rejection due to decreased plasma concentrations of ciclosporin below therapeutic
thresholds.
Further research revealed that St. John’s wort can compromise the effectiveness of several
medications by accelerating their elimination from the body—either through induction of
metabolic enzymes or activation of the P-glycoprotein drug transporter. Drugs known
to be affected include warfarin, digoxin, tricyclic antidepressants, simvastatin, and
various others.
Medicinal Uses
Symptomatic treatment of mild and moderate depressive episodes.
Externally for the treatment of minor cuts, burns and skin ulcers. Topically for viral
infections.
Warning / Pregnancy:
St. John’s wort is considered potentially unsafe for oral use during pregnancy. Animal
studies have indicated that it may cause birth defects in developing rat fetuses; however,
its effects on human pregnancy remain unconfirmed.
Because the herb can increase sensitivity to light, individuals taking St. John’s wort should
avoid direct exposure to sunlight and tanning beds. When outdoors, it is recommended
to wear protective clothing and apply broad-spectrum sunscreen with an SPF of 30 or
higher.
Concurrent use with other medications known to heighten photosensitivity—such as
certain antibiotics or sulfonamide drugs—should be avoided, as this may increase the
risk of phototoxic reactions.
Drug Interactions
MAO inhibitor: St. John's Wort contains some weak monoamine oxidase inhibitor
(MAOI) properties that may add to the effects of other MAOI drugs, therefore theoretically
increasing the risk for hypertensive crisis.
Beta-sympathomimetic amines: It is prudent to avoid concomitant use with beta-
sympathomimetic amines, e.g., ma huang or pseudoephedrine.
SSRIs (Fluoxetine): together with St. John's wort (has SSRI activity) can increase the risk

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