Merck Manual

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Drug Interactions With St. John's Wort

Drug Interactions With St. John's Wort

Affected Drugs

Interaction

Benzodiazepines

St. John’s wort may reduce the effectiveness of these drugs in reducing anxiety and may increase the risk of side effects such as drowsiness.

Cyclosporine

St. John’s wort may reduce blood levels of cyclosporine, making it less effective, with potentially dangerous results (such as rejection of an organ transplant).

Digoxin

St. John’s wort may reduce blood levels of digoxin, making it less effective, with potentially dangerous results.

Iron

St. John’s wort may reduce iron absorption.

Monoamine oxidase inhibitors (MAOIs)

St. John’s wort may intensify the effects of MAOIs, possibly causing very high blood pressure that requires emergency treatment.

Nonnucleoside reverse transcriptase inhibitors

St. John’s wort increases the metabolism of these drugs, reducing their effectiveness.

Oral contraceptives

St. John’s wort increases the metabolism of these drugs, reducing their effectiveness.

Omeprazole

St. John’s wort decreases serum concentrations of omeprazole, reducing its effectiveness.

Photosensitizing drugs (such as  amiodarone, naproxen, sulfonylureas [such as glipizide], and sulfonamide antibiotics)

When taken with these drugs, St. John’s wort may increase the risk of sun sensitivity.

Protease inhibitors (such as indinavir or saquinavir), which are used to treat human immunodeficiency virus [HIV] infection

St. John’s wort may reduce blood levels of protease inhibitors, making them less effective.

Selective serotonin reuptake inhibitors (SSRIs, such as fluoxetine, paroxetine, and sertraline)

St. John’s wort may intensify the effects of these drugs.

Tricyclic antidepressants

St. John’s wort may decrease the effects of these drugs.

Warfarin

St. John’s wort may reduce blood levels of warfarin, making it less effective and clot formation more likely.