Journal of Geriatric Psychiatry and Neurology. Drug Interaction Advisory NIH Clinical Center research shows that St. John s wort may reduce the effectiveness of several drugs by speeding up activity in a key pathway responsible for their breakdown. The end result is that blood levels of these drugs decrease because the body breaks them down faster. Doctors and patients should be aware of these negative drug interactions that could interfere with the proper functioning of these drugs. This publication is not copyrighted and is in the public domain.
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