Which two routes have the quickest route to the brain?

• A. Inhalation
• B. Injection
• C. Inhalation and Injection
• D. Oral

Answer: (C)

The quickest path to the brain comes from routes that deliver the drug into the bloodstream immediately, bypassing the digestive system. Inhalation does this by absorbing through the lungs’ alveoli, where a large surface area and rich blood supply allow rapid entry into the bloodstream and quick brain effects. Injection, especially intravenous, dumps the substance directly into the bloodstream, so it reaches the brain via arterial circulation in moments. Oral intake, in contrast, has to travel through the stomach and intestines and then undergo liver metabolism before reaching the brain, which slows onset. So inhalation and injection provide the fastest routes to the brain.