I am a special needs teacher and have two children in my class with adhd. I have also been a nanny for a family of 5 kid, 2 of which had adhd.
It does take a long time to diagnose the condition and medication doesn't always work. Luckily they are finding more and more about what works every day. There are several different drugs on the market, ritalin/concertia types drugs can work for 4 or 8 hours depending if they are slow release. These drugs work whilst they are in the system only. There is a new drug on the market but I forget the name. This builds up in the body over 4-6 weeks but works for 24 hours at a time. There are less side effects with the second type of medication. The side effects with ritalin can be increased/suppressed apetite, weight loss, insomnia and agressive behaviour as the medication wears off.
Hope some of this info helps, can answer questions aswell.