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St John's Wort Heart Side Effects

author image Shelley Moore
Shelley Moore is a journalist and award-winning short-story writer. She specializes in writing about personal development, health, careers and personal finance. Moore has been published in "Family Circle" magazine and the "Milwaukee Sentinel" newspaper, along with numerous other national and regional magazines, daily and weekly newspapers and corporate publications. She has a Bachelor of Science in psychology.
St John's Wort Heart Side Effects
St. John's Wort side effects on the heart are uncommon. Photo Credit: Popartic/iStock/Getty Images

Hypericum perforatum, commonly known as St. John's Wort, is an herbal remedy people primarily use for treating anxiety, depression and insomnia. Many side effects are possible, such as dizziness, dry mouth, fatigue, headache, increased sensitivity to sunlight, upset stomach and sexual dysfunction. Using St. John's Wort also can affect the heart, although this is not common.

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Normal Use

Side effects involving the cardiovascular system during normal use of St. John's Wort are uncommon. Anyone experiencing these side effects should seek immediate medical attention. They include rapid heartbeat (tachycardia), a forcefully-beating heart or heart pounding (palpitations) and high blood pressure (hypertension), as listed by eMedTV.

Decreasing Drug Efficacy

St. John's Wort can elevate liver enzyme activity, which can reduce blood levels of other medications as the liver filters the blood. This can make medications less effective. Additionally, St. John's Wort may reduce absorption of some medications from the digestive tract, further lowering their effectiveness. This can be dangerous when it involves drugs such as heart medication. The National Center for Complementary and Alternative Medicine (NCCAM) specifically lists digoxin as a medication that can be affected by St. John's Wort. Digoxin strengthens heart muscle contractions, and doctors prescribe it for congestive heart failure and abnormal heart rhythm (arrhythmia).

Serotonin Syndrome

Taking St. John's Wort with certain other medications, such as antidepressants or drugs to treat migraine headaches, can increase the risk of a dangerous condition called serotonin syndrome. This might also happen with an overdose of St. John's Wort. Serotonin syndrome can cause tachycardia along with many other symptoms, including elevated blood pressure, muscle rigidity, fever and confusion. It can lead to coma and death.

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