Comedown - Cocaine: Why short half-life but long insomnia?

[gn2osis]

Cocaine's half-life is about an hour. So why is it so hard to
fall asleep for several hours after using it? Much lower
threshold for residual stimulation than for the desired euphoria?
Lots of dopamine or NE still washing around? What is it exactly
that the body needs to repair, once the cocaine's been metabolized, in
order to go beddy-bye?<!--
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