Final answer:
Drugs that are injected have a rapid onset because they are absorbed directly into the bloodstream.
Step-by-step explanation:
Drugs that are injected have a rapid onset because they are absorbed directly into the bloodstream. When a drug is injected, it bypasses the digestive system and enters the bloodstream directly, resulting in a quicker and more immediate effect. Examples of drugs that are commonly injected include insulin for diabetes treatment, vaccines, and certain medications administered in a healthcare setting.