Atrial fibrillation (AF) is the most common arrhythmic disorder. Because of the irregular heartbeat, blood is allowed to pool in the atria, which can cause blood clots to form. Administering an anticoagulant such as rivaroxaban is a primary treatment. During client instruction, the nurse tells the client about the side effect of possible bleeding; the client should notify the health care provider if it occurs. Other medications are used to control the heart rate or strength of the heartbeat. Because the medication is carefully calculated, clients should never take a double dose. If a dose is missed, the client resumes the medication per prescribed schedule.