What severe effect can occur with overdosing on sedative hypnotics?

The severe effect that can occur with overdosing on sedative hypnotics is respiratory and cardiac depression. Sedative hypnotics, such as benzodiazepines and barbiturates, are designed to depress the central nervous system. When these substances are taken in excessive amounts, they can significantly slow down vital functions, particularly respiration and heart rate, which can lead to life-threatening situations.

This profound depression of the respiratory system can result in inadequate oxygenation of the body, potentially leading to hypoxia, coma, or even death. Likewise, cardiac depression can lead to arrhythmias or a complete failure of cardiac function. Because these effects compromise critical bodily functions, they represent serious and immediate medical emergencies that require prompt attention.

In contrast, the other options do not accurately characterize the outcomes of sedative hypnotic overdose. Increased energy is contrary to what happens with these medications; they induce relaxation and sedation rather than stimulation. Psychological instability may be a concern with misuse or withdrawal but is not the primary severe risk associated with overdose. Enhanced memory recall is generally not a characteristic of sedative use; these substances can often impair cognitive functions and memory rather than enhance them.