Surviving surgery; succumbing to pharmacotherapy: A case report underscoring the importance of PRN order clarification for patient safety.

"Pro re nata" (PRN) or "as needed" medicine administration and usage is a relatively neglected area in medication management (pharmacotherapy/pharmaceutical care) which contributes to error-prone use of medications and is unsafe for patients. In this case, we report the incident of diclofenac toxicity in a 51-year-old woman due to a prescription of 100 mg diclofenac suppositories PRN, or as needed, for postoperative pain control without explanation of the maximum daily dose (150 mg daily), which led to arbitrary consumption of 3 g of diclofenac over 5 days (600 mg daily) by the patient, and subsequent development of metabolic acidosis, acute kidney injury, and sudden cardiac arrest. The implementation of practical guidelines and training programs for health care workers to appropriately prescribe, dispense, and administer PRN medicines are necessary, and should at least include providing clarification for their indication, dose and frequency, as well as any cautionary instructions to ensure safe and effective use of such medicines.