THEORETICAL CAUTIONS AND CONTRAINDICATIONS — St John's wort is contraindicated in pregnancy (based on animal studies, Grush 1998). Use with caution in individuals taking digoxin (may alter levels of this medication, Johne 1999). It is not for use in severe depression. Use with caution in individuals taking other antidepressants (Gordon, 1998). Based on its pharmacological activity, St John's wort may alter the actions of monoamine oxidase (MAO) inhibitors, tricyclic antidepressants, and selective serotonin reuptake inhibitors (SSRIs) (Chatterjee, 1998; Bennett, 1998). May elevate hepatic transaminases (noted animal studies at high doses) (Brockmoller, 1990). May cause photosensitivity (based on animal studies and a human clinical trial) (Brockmoller, 1997). Use with caution in individuals on reserpine (effects may be antagonized by St John's wort) (Okpanyi, 1987). Use with caution in individuals on narcotic medications (based on animal studies, may enhance sedation from these drugs) (Okpanyi, 1987).
May cause drowsiness (mild). Based on pharmacological activity, use with caution while driving or operating machinery. Caution in individuals taking sedative medications (eg, anxiolytics, benzodiazepines). Effects may be additive with other CNS depressants or natural products with sedative properties.
Antidepressant therapy may precipitate a shift to mania or hypomania in individuals with bipolar affective disorder (Schneck, 1998).
Three patients experienced mania after short-term St John's wort use. All returned to normal after discontinuing the product.
St John's wort may induce the cytochrome P450 enzyme system, although there is conflicting information about this claim. Specifically, data indicates probable interactions between St John's wort and the HIV-1 protease inhibitor indinavir (Piscitelli, 2000) and between St John's wort and the antirejection medication cyclosporine (Ruschitzka, 2000). Additionally, enzyme induction may result in decreased estrogen levels in individuals taking oral contraceptives (Yue, 2000). While the FDA has issued a public health advisory regarding this issue, the authors recommend considerable caution be exercised before adding St John's wort to any medication regimen containing a cytochrome P-450 3A substrate.
St John's wort may cause an increase in thyroid-stimulating hormone (Ferko, 2001; Hauben, 2002