A nurse is assessing a client receiving codeine for a persistent cough caused by upper respiratory infection. Which finding would require the nurse to intervene?

A. Client experiences respiratory depression: Codeine is an opioid agonist that suppresses the medullary cough center and can concurrently depress the respiratory drive. A significant reduction in respiratory rate or tidal volume indicates systemic toxicity and compromised gas exchange. This life-threatening adverse effect necessitates immediate clinical intervention. B. Dry mouth persists throughout the day: Xerostomia is a common anticholinergic-like side effect associated with various opioid medications used for antitussive purposes. While uncomfortable for the patient, it does not represent an acute physiological threat or a failure of the therapeutic regimen. It is managed with oral hygiene. C. Client reports mild drowsiness after each dose: Opioids cross the blood-brain barrier and exert sedative effects on the central nervous system. Mild somnolence is an expected pharmacological response and generally does not require intervention unless it progresses to an altered level of consciousness. It is a predictable side effect. D. Coughing partially improves but persists at night: The therapeutic goal of codeine in an upper respiratory infection is the symptomatic relief of a non-productive cough. Partial improvement suggests the medication is reaching therapeutic levels but may not completely abolish the reflex. Persistent coughing is a clinical observation.