Final answer:
The nurse's priority action after administering medication via the incorrect route is to assess for adverse reactions, then notify the healthcare provider, closely monitor the client's vital signs, and document the error in the medical record.
Step-by-step explanation:
When a nurse accidentally administers medication via the wrong route, as happened with the orally dissolving mirtazapine given through a percutaneous endoscopic gastrostomy tube instead of sublingually, the nurse's priority action should be to assess the patient for any adverse reactions. Following this immediate assessment, the nurse should then notify the healthcare provider about the error. This is critical for two reasons: it ensures that the healthcare provider is aware of the deviation from the prescribed treatment and can give appropriate orders for any necessary interventions, and it promotes transparency and adherence to hospital protocols regarding medication errors. After notifying the healthcare provider, the nurse should closely monitor the client's vital signs to detect any changes that may indicate an adverse reaction or complication from the incorrect administration route. Finally, the nurse should document the error in the medical record, including the specifics of the incident, actions taken, and any orders received from the healthcare provider. Administering the correct medication via the correct route may be indicated afterward, based on the healthcare provider's guidance.