The doctor said: It is not widely known how natural products can affect the risk of prolonged QT. However, we know that some natural products can increase the concentration of medications in your blood, which could increase the risk of QT prolongation. For example, valerian could increase the concentration of Paxil. The risk of cardiac problems due to QT prolongation is low, but the consequences can be serious if it occurs, so I would advise against taking this natural product. Regarding echinacea, it appears to be safe based on the available data in your case. Other interactions to watch out for include natural products used for weight loss, which can cause dehydration and low potassium levels in the blood, which can further prolong your QT. To sum up, I recommend consulting with your pharmacist before taking any natural product.