To the OP - people in this thread (and a lot of others on FT) recommend Ambien. You may decide that Ambien is a good thing for you for this trip. If you do and have never taken Ambien before, it would be a good idea to try it at home first. Ambien has had some reasonably rare but severe side effects, and 35,000 feet in the air halfway between MIA and MAD is no place to encounter those.

Also, MIA-MAD is a relatively short flight. It would be a good idea to set your alarm on your test night for the amount of time you will have for sleep on this flight (I would suggest 7 hours) and see what you function like upon awakening. Some people feel groggy.

All that said, many people here are quite happy with Ambien and you would likely be among them.