In managing a client with atrial fibrillation, which medication should be administered first?

In managing a client with atrial fibrillation, the administration of diltiazem as the first-line medication is appropriate due to its role as a calcium channel blocker that helps in rate control. Atrial fibrillation often leads to an uncoordinated atrial contraction and can result in a rapid ventricular rate. Diltiazem effectively decreases heart rate by slowing down conduction through the AV node, which is crucial for stabilizing the client and preventing complications related to rapid ventricular response.

While rivaroxaban is an anticoagulant used for stroke prevention in atrial fibrillation, it is not the immediate treatment for rate control. It takes time for anticoagulants to reach therapeutic levels and does not address the immediate management of tachycardia associated with atrial fibrillation.

Drawing blood for a thyroid function test is a diagnostic step that may be warranted in cases of atrial fibrillation, especially in younger patients or those without traditional risk factors; however, it does not provide immediate treatment for the arrhythmia.

An echocardiogram, while useful for evaluating structural heart issues or assessing left atrial size, is also not an immediate intervention for rate control in the context of acute management of atrial fibrillation.

Therefore, administering