One who is seemingly addicted to the sensation of exhilaration associated with risky behaviors or exciting situations, and who actively seeks such opportunities.
madcap
noun
An impulsive, hasty, capricious person.
adj
Hasty, impulsive, or reckless; capricious.
How often have the words adrenaline junkie and madcap occurred in a corpus of books? (source: Google Ngram Viewer )