Which of the following is a key step in the preparation of a transdermal patch?

Cleaning the skin where the patch will be applied is essential in the preparation of a transdermal patch. This step ensures that the skin is free from dirt, oils, and other contaminants that could interfere with the adhesion of the patch and the absorption of the medication. A clean application site helps to maintain the integrity of the patch and promotes effective drug delivery, ensuring that the medication can penetrate the skin barrier effectively and enter the systemic circulation as intended. This practice enhances the effectiveness of the treatment and minimizes the risk of irritation at the site of application.

Other steps, while they may appear relevant, do not address the same fundamental need for proper application hygiene and medication absorption. For instance, shaking the patch could disrupt the active ingredients, measuring the application area is typically unnecessary if the patch is appropriately sized, and peeling the patch back might lead to exposure to contaminants or reduced adhesion. Therefore, proper cleaning of the skin is a crucial step not only for effective treatment but also for patient safety.