Final answer:
The nurse should contact the PHCP if the client prescribed isotretinoin for severe acne is also taking Vitamin A. This combination can lead to hypervitaminosis A, which can cause serious side effects.
Step-by-step explanation:
If a client with severe acne is prescribed isotretinoin by the primary health care provider (PHCP), and the nurse reviews the client's medication record, it would be important for the nurse to contact the PHCP if the client is also taking Vitamin A. Isotretinoin is a powerful retinoid, similar in structure to Vitamin A, and taking both together can lead to a risk of hypervitaminosis A, which can cause symptoms such as nausea, vomiting, and headache, among other more severe side effects. Vitamins C, D, and E do not have the same reported interactions with isotretinoin and are less likely to raise concerns when used concurrently with this medication.