I recently acquired some and had quite an embarassing time with it, which was all my fault of course.
First I measured out 6 mg on a 2mg accurate scale, and since it doesn't get any result below 6 mg usually I decided just to take what looked like half the powder. I just did this orally, not sublingually, which was an oversight since I normally take benzos under the tongue.
Anyway, I didn't notice much at first, so I started to make a batch for liquid measurement. I put a gram (minus what I had already taken) and mixed it with 100 ml vodka. This didn't dissolve very well so I put it on a hot water bath (lid on vodka to prevent evaporation). This did the trick. All the remaining phenazepam dissolved within at max a half hour.
At this point the original oral dose began kicking in good, and it being 3 mg (which is 6 times the therapeutic dose) it did a grand job of eliminating my inhibitions. I decided I'd inject some of the vodka solution. I used a micropore filter wheel just to be totally safe.
I IV'd approximately 2-5 mg of vodka, phen, and saline. I think I got two IV shots in. One had a lot more vodka in it because it stung a bit and my vein was sore the next day.
Now there I was, on anywhere between 7 and 13 mg of phenazepam, and I'm feeling very good. And that's when I decided to IM. I don't remember this part, or much of the next week. My IM syringes hold 10cc's, so it's entirely possible I injected 100mgs of phenazepam. I really don't know.
The next thing I know it is the next day and my girlfriend is somehow in my apartment, very angry and curious as to my strange behavior and needle marks. Apparently it took her a long time to get any meaningful information out of me, since I was slipping in and out of consciousness and could form only fragmented sentences. There was a strange sawdust material all over my kitchen floor that no one could explain.
She spent the next three days caring for me, during which she claimed my body temperature was very low, my breathing shallow, and my heart rate low. But my bouts of consciousness gave her hope, and she didn't call the ER. I came out of it and was close to normal enough by the end of the week to go on a road trip, but my memory of this is like swiss cheese. I barely remember anything from that week.
tl;dr: Be careful with dosing this stuff. Even with good scales and proper liquid measurement techniques, the benzo assault on inhibitions may mean you take far more than you wanted. I could have taken anywhere between 8 and 113 mg of phenazepam, and while this isn't what I sought out to do it's what I ended up doing.
I guess this could have happened to anyone who overdoes there benzo intake, but since this page seems lacking in actual experiences I'd add mine.
BTW, the drug high was fairly nice, euphorically opiate-like when you come to the next day. I'm not sure what it's like at lower doses. I caution anyone to try what I did, since the recommended dose is half a milligram.