What potential harmful effect should be discussed with a patient starting garlic therapy while on dual antiplatelet therapy?

When a patient starts garlic therapy while on dual antiplatelet therapy, discussing the increased risk of bleeding is crucial. Garlic has been shown to have antiplatelet effects, which can potentiate the effects of medications like aspirin and clopidogrel that are commonly used in dual antiplatelet therapy. This combination can lead to an enhanced risk of bleeding complications, as the additive effects on platelet aggregation may impair the body's ability to form clots effectively.

The possible interactions between garlic and antiplatelet medications highlight the importance of monitoring for signs of bleeding, such as unusual bruising, prolonged bleeding from cuts, or gastrointestinal bleeding. Patients should be advised to report any such symptoms immediately.

While other adverse effects like QT prolongation or tachycardia could be considerations with some herbal therapies and medications, they are not directly linked to garlic in the same manner as the increased bleeding risk. Similarly, garlic is typically not associated with increased blood pressure; in fact, some studies suggest it may have a blood pressure-lowering effect. Therefore, the primary concern with garlic supplementation in the context of dual antiplatelet therapy is indeed the increased risk of bleeding.