An adult patient suddenly cries out. A nurse sees the patient's head twisted to the side and arched back and the eyes rolled up. The patient has been newly diagnosed with schizophrenia, and therapy with a traditional antipsychotic medication was started yesterday. Based on the nurse's assessment, what would be the next nursing action?
A. Obtain the patient's vital signs and pulse oximetry
B. Administer a prn dose of diphenhydramine (Benadryl)
C. Administer a prn dose of haloperidol
D. Obtain a serum drug level and reassure the patient