What is the primary function of the lockout mechanism on a PCA pump?

Rationale: A. The lockout mechanism ensures a safe interval between doses, preventing overdose while allowing the client control of pain management. B. PCA pumps provide patient-controlled doses, not a continuous constant infusion (unless a basal rate is ordered separately). C. Only the patient should press the PCA button; family-administered doses increase the risk of oversedation and respiratory depression. D. Nurses adjust PCA settings at the bedside under provider orders, not remotely. The lockout mechanism is not designed for nurse control but for patient safety.