Which side effect of glinide repaglinide requires immediate action from the nurse?

Lethargy is a side effect of the glinide repaglinide that warrants immediate action from the nurse because it may indicate a significant drop in blood glucose levels, leading to hypoglycemia. Repaglinide is an insulin secretagogue that stimulates the pancreas to release insulin. If a patient experiences lethargy, this could signal the onset of hypoglycemia, which is a medical emergency requiring prompt assessment and intervention to prevent severe complications such as loss of consciousness or seizures.

In contrast, while headache, nausea, and fatigue can also be uncomfortable and may impact the patient's well-being, they are typically not considered acute medical emergencies that require immediate nursing intervention. These symptoms can often be managed with supportive care and may not pose an immediate threat to the patient’s safety. Thus, the presence of lethargy as a more severe indicator reflects a potential crisis situation that needs urgent attention.