Cold and clammy skin, dilated pupils, shallow breathing, and weak and rapid pulse are overdose symptoms resulting from which of the following substances?

The symptoms described—cold and clammy skin, dilated pupils, shallow breathing, and a weak and rapid pulse—are indicative of an overdose specifically associated with barbiturates. Barbiturates are central nervous system depressants that can lead to respiratory depression and cardiovascular instability, which correspond with the physical signs mentioned.

In an overdose scenario, the body struggles to maintain adequate physiological functions due to the depressant effects of the substance. Cold and clammy skin results from the cardiovascular compromise, while shallow breathing and a weak, rapid pulse highlight the severity of respiratory and circulatory effects. Dilated pupils can also be observed in severe depressant overdoses due to the body's response to decreased oxygen levels.

The other substances listed interact with the nervous system differently and do not typically manifest these specific symptoms in overdose situations. For instance, cocaine is a stimulant and is more commonly associated with increased heart rate and other hyperactive symptoms, while heroin—which is an opioid—might cause pinpoint pupils and slower pulse, not the cold, clammy skin or rapid pulse described in the question. Methylphenidate, another stimulant, similarly leads to increased alertness and heart rate rather than the depressive signs noted.

This correlation helps to clearly establish that bar