The Client Is Being Ordered Robitussin DM

The client is being ordered Robitussin DM. He complains of experiencing dizziness. What is the highest priority nursing intervention?

A) Call the physician; this is indicative of an anaphylactic reaction to the medication.
B) Call the physician; this is an expected side effect of the medication.
C) Call the pharmacist; this is evidence that the drug was prepared incorrectly.
D) Call the pharmacist; this is evidence that this is not the correct drug.