I've been on morphine for back pain for over six years,and I can tell you that you do not want to fuck with 100mg first time. If you take 100mg of time release orally, it takes 12 hours to dissolve in your gut, so that's like taking about thirty mg every four hours. There's some info on peak absorption rates at www.rxlist.com,
but that's roughly it. If you crush it or something to beat the time release factor, you are taking it all at once. Think of it this way: if you are in a car accident and cut your leg off with a piece of twisted jagged steel, they will hit you with 10mg. After six years, I take 100mg at a time, but if I make an error and double up, I get very, very sleepy. I can't get a buzz anymore; after a while that stops working and the best you can hope for is a totally screwed up night's sleep. Morphine in large doses causes a weird type of insomnia, where you can't stay awake, but you can't stay asleep, either. You get some extremely strange dreams, though.
Anyways, DO NOT
take 100mg the first time, or even if you haven't taken any for several weeks. Your tolerance goes back down, too. My advice: 30mg is all the marbles, and try that with great caution, like have somebody straight with you.