Which of the following is NOT a characteristic of barbiturates?

Barbiturates are a class of medications that primarily act as central nervous system depressants, which means they are used to produce sedation, induce sleep, and manage anxiety. Option A states that they increase blood pressure, which is not a characteristic of barbiturates. In fact, barbiturates tend to have a sedative effect, often leading to decreased blood pressure rather than an increase. The other options accurately reflect characteristics of barbiturates: they do decrease respiration rate as part of their depressant action, affect heart rate, and are indeed classified as central nervous system depressants. Understanding the effects of barbiturates is crucial for recognizing their potential risks and therapeutic applications in medical practice.