Which agent is known for its fast onset and short duration of action?

Succinylcholine is known for its fast onset and short duration of action, making it a commonly used agent in clinical settings for rapid sequence intubation and in anesthesia. As a depolarizing neuromuscular blocker, it works by mimicking acetylcholine at the neuromuscular junction, leading to rapid muscle paralysis. Its effects typically begin within one to two minutes after administration, and it is quickly broken down by plasma cholinesterase, resulting in a short duration of action, generally lasting around 5 to 10 minutes.

In contrast, the other agents listed have different pharmacological profiles. Atropine, while it has a relatively fast onset, its duration of action is longer, often lasting several hours, which is not consistent with the short duration characteristic required in this question. Scopolamine has a longer onset and duration as well, primarily used for motion sickness and other indications, where prolonged effects are beneficial. Glycopyrrolate also has a longer duration of action, typically used to reduce secretions and prevent bradycardia in surgical settings. Thus, only succinylcholine aligns with the criteria of fast onset and short duration of action.