A patient diagnosed with bipolar disorder is prescribed lamotrigine. The nurse should instruct the patient to immediately report which adverse effect?

A. Nausea is a common side effect but is not as critical as a skin rash. B. Tremors may occur with certain medications used in bipolar disorder but are not a specific concern with lamotrigine. C. A skin rash is a serious adverse effect of lamotrigine, as it can indicate a life-threatening condition called Stevens-Johnson syndrome (SJS) or toxic epidermal necrolysis (TEN), which require immediate medical intervention. D. Drowsiness may occur with many medications but is not as urgent as a skin rash in this case.