Here's the caffeine paradox:
When a cell in your body "eats" a piece of glucose something comes out the back end and that's adenosine. As adenosine works its way through your blood stream, it goes into one particular spot in your brain with particular receptor sites. As these receptor sites receive or fill up with more and more adenosine, you usually get more and more sleepy. This is your Sleep Drive. When adenosine binds to its receptors, neural activity slows down, and you feel sleepy (this would most likely not apply during Benzo-induced insomnia)?
The molecular structure of adenosine and caffeine are only off by one molecule! So caffeine fits perfectly into that same receptor site in your brain and blocks adenosine from attaching and making you sleepy. That's why caffeine keeps you awake. And that's why many get a "caffeine crash" or feel tired and sleepy after the caffeine they consumed leaves the receptor sites and adenosine comes rushing back in. Again this probably wouldn't apply during Benzo-induced insomnia?
The average half-life of caffeine in plasma of healthy individuals is about 5 hours. However, caffeine's elimination half-life may range between 1.5 and 9.5 hours depending on the person (Brachtel and Richter, 1992; Busto et al., 1989). With that said, How long does it take for say 100mg (roughly the amount in a cup of coffee) of caffeine to wear off? Using the 5 hour half life, that means if you consume 100 mg of caffeine, after 5 hours, you'll still have 50 mg left in your body and 25mg left another 5 hours after that. Depending on when you consume caffeine, it could easily keep you up at night especially with a sensitive central nervous system coming off of Benzos?
But not sleeping well (or at all) usually leads to you looking for something to keep you alert, so people reach for more caffeine which can create a vicious cycle?
