Final answer:
The instruction that should not be given to a patient prior to nitrous oxide sedation is to consume a large meal right before the appointment.
Step-by-step explanation:
The instruction that should not be given to a patient prior to nitrous oxide sedation is to consume a large meal right before the appointment. Eating a large meal before the procedure can make the patient feel sleepy and may affect their ability to think clearly. It is important for the patient to avoid eating for two hours before the procedure, inform the dentist of any respiratory conditions, and avoid alcohol for at least 24 hours before the procedure.