Honestly I would stay as far away from sedatives and drugs as you can.
One, because if you make it through the first flight without medication then all subsequent flights will be that much easier. You'll say to yourself, "Hey! I did it once without sedatives I can do it again!"
And two, it's a cheap way to get over a fear. You can't overcome anything unless you face it head on. A lot of people use drugs for things like this and they are fine with that, but think how much more confidence you will have if you overcome this without medication.
Lastly why do you think airports have bars?

My sister is petrified of flying as well, or rather she
was. The first time she flew I had to pry the Xanax from her hands, but after a shot at the bar she was significantly relaxed. It was a better and safer option than drugs and it made the flight just as easy for her had she taken something. There is less chance of an allergic reaction that way if you have never taken something like Xanax before.
Try to distract yourself with little facts as well. One good thing is to learn facts about the mechanics of airplanes. On our liftoft I distracted her with a running comentary of slat deployment and their function on airplanes. The rest of the way until she fell asleep I talked about the jet engines and wing designs. She was utterly fascinated and too busy trying to figure out how things worked to let her fear conquer her. (And mind you she is very prone to anxiety attacks normally!)
There are two steps that are key in conquering a fear. One facing it head on like you are planning to. And two, understanding what it is that you are afraid of. I had the same problem with sharks. When I was younger I was in the water during a shark attack, less than 8 feet away from the person attacked. I was terrified of all water but after studying sharks have learned enough about them to feel comfortable with the precautions I do take when in water. Then I faced them head on and I now make it a point to swim with them at least once every other year. Now thats a bit different than flying, but I went through the same anxiety. I got into the water and wow was my heart pounding. My breathing was very erratic when the first shark swam under me and it took me awhile to get it under control. But once I had I started distracting myself with facts. Like how they use their lateral line system to sense their surroundings and their dorsal fins to manuever. Now I understand planes are very different from sharks but the same concept applies. If you understand how the object of your fear works you'll calm down. The take off wont be pleasant, but I assure you that you can handle it.
Bring reading material as well. That helps a lot, or a portable DVD player as someone else already suggested. I'd say try to sleep, but when you are trying to fall asleep your mind wanders and thats not good when your afraid of something at that present moment. Stick with distractions.
Plus a little shot of Jose can go a long way in calming those nerves to.

Best of luck with it! Feel free to PM me if you need any plane facts to distract yourself with.