Final answer:
A medical assistant should apply a transdermal patch to a hairless area of the patient's skin to ensure proper adhesion and medication absorption, avoiding placing the patch on the forearm.
Step-by-step explanation:
When applying a transdermal patch for a patient, the medical assistant should take the following action: Apply the patch to a hairless area of the patient's skin. This is important because hair can impede the adhesion of the patch and potentially interfere with medication absorption. Additionally, each patch comes with manufacturer instructions indicating the best sites for application, which often include areas like the upper arm, chest, back, or flank, avoiding bony areas and skin folds. The forearm is not typically a recommended site since it's more likely to rub against clothing or be in motion, which could cause the patch to loosen or fall off. Furthermore, the assistant must ensure the skin is clean, dry, and free from creams or oils before application.