Diurex Side Effects on the Heart

Updated July 19, 2017

Alva-Amco manufactures Diurex as a non-prescription medication intended for use as a diuretic and pain reliever. People with non-emergent symptoms such as those associated with premenstrual syndrome or trouble urinating may elect to try Diurex before seeking more potent therapies. Although the two main components have only mild effects on the body, both may pose consequences for the cardiovascular system and caution should therefore be used when taking Diurex.


Caffeine serves as the primary active diuretic ingredient in Diurex. One pill contains 50 mg, which does not harm the heart. Taking multiple pills that provide caffeine in excess of 100 to 200 mg may cause tachycardia (a heart rate in excess of 100 beats per minute) or irregular heartbeat. The risk increases with the number of times that you take this amount. Consult your doctor before using Diurex if you already have a high resting heart rate or an arrhythmia.

Blood Thinning

Diurex contains the pain reliever magnesium salicylate, which as a side effect reduces the formation of clots. This benefits people at risk of stroke or thrombosis; however, those patients likely already take other medications to treat for those conditions. If you currently take pills to reduce blood clotting--such as Plavix or a daily aspirin--ask a doctor whether the addition of Diurex will thin your blood too much.


All diuretics can lower blood pressure to varying degrees. Depleting some of the liquid content from the blood slows blood flow and eases the passage of red cells and plasma through the vessels. This effect is typically desired. However, Diurex is not indicated for hypertension because the caffeine in it raises blood pressure by its action on the heart. Consult your doctor concerning any other medications you take and your risks for hypertension. Be sure to monitor your blood pressure if you take Diurex for an extended period.

Reye's Syndrome

Diurex should not be given to children. In addition to the negative effects caffeine can cause on young hearts, salicylates such as those found in Diurex have been associated with Reye's Syndrome. This disease attacks every organ in the body, including the heart, by depositing fat in places where it doesn't belong. Even if the syndrome is diagnosed early and treated successfully, there can be lasting damage to the heart muscle and arteries.


The most significant cardiac danger associated with prolonged diuretic use or overdose stems from lowered potassium levels. Potassium plays a central role in muscle action, and the heart works harder than any muscle in the body. Hypokalemia (low potassium) interferes with regulation of the heartbeat and results in fatal arrhythmias if left untreated. Never take more pills than the Diurex instructions recommend.

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About the Author

Daniel Annear has been a writer, editor, and teacher since 1998. He held the editorship of the "Descant Literary Magazine" for three years, and taught literature at Trident Technical College in Charleston, S.C. He holds a Bachelor of Arts degree in English from King College.