First, let’s define what “drug” means – from Google’s search results, a drug is “a medicine or other substance which has a physiological effect when ingested or otherwise introduced into the body.”
The FDA considers caffeine a drug, and many people consume caffeine everyday by drinking coffee, tea, or soda.
What does caffeine do to your body?
Caffeine works by stimulating the central nervous system (CNS), heart, muscles, and the centers that control blood pressure. Caffeine can raise blood pressure, but might not have this effect in people who use it all the time.
https://www.webmd.com/vitamins/ai/ingredientmono-979/caffeine
What is a safe amount of caffeine to consume?
Caffeine affects each person differently. Research is starting to show how and why certain people metabolize caffeine easier than others.
How long does caffeine stay on your system?
Caffeine begins to affect your body very quickly. It reaches a peak level in your blood within 30 to 60 minutes. It has a half-life of 3 to 5 hours. The half-life is the time it takes for your body to eliminate half of the drug. The remaining caffeine can stay in your body for a long time.
American Academy of Sleep Medicinehttps://sleepeducation.org/sleep-caffeine/