Final answer:
The correct term to document in the medical record for an itchy rash with raised, pinkish lesions after an antibiotic injection is urticaria, which is commonly known as hives.
Step-by-step explanation:
When a medical assistant observes a patient developing an itchy rash with pinkish, raised lesions after administering an antibiotic injection, the correct term to use when documenting this finding in the patient's medical record is urticaria. Urticaria, commonly referred to as hives, is characterized by the sudden appearance of raised, itchy areas on the skin.
Erythema is simply the medical term for redness of the skin, purpura refers to purple-colored spots that are caused by internal bleeding, and petechiae are tiny, pinpoint, red dots that are a result of bleeding under the skin. In this case, the described skin lesions and rash are consistent with urticaria, which often occurs as an allergic reaction to a substance, like an antibiotic.