A patient with respiratory depression and pinpoint pupils is likely intoxicated by which substance?

The symptoms of respiratory depression and pinpoint pupils are strongly indicative of opioid intoxication, with heroin being a prime example of such a substance. Opioids, including heroin, depress the central nervous system, leading to a decrease in respiratory drive—resulting in respiratory depression. Additionally, one of the hallmark signs of opioid intoxication is miosis, or pinpoint pupils, which occurs due to the effects on the autonomic nervous system.

In contrast, cocaine is a stimulant that typically causes symptoms such as increased heart rate, heightened alertness, and dilated pupils. Alcohol can cause respiratory depression as well, but it does not usually cause pinpoint pupils; rather, it can lead to a broader range of symptoms including ataxia and slurred speech. Marijuana's effects are also different, primarily leading to alterations in perception and motor function rather than the specific signs seen with opioid use.

Thus, the combination of respiratory depression and pinpoint pupils strongly aligns with heroin overdose, confirming its identification as the correct answer.