There are a number of prescribed medications available to treat ADD/ADHD. These include the following.

Methylphenidate

These include Ritalin® and Equasym®. These medications contain Methylphenidate Hydrochloride. This can work to enhance the activity of certain underactive areas of the brain and can aid concentration, as well as calming a restless or overactive child.
It must be given under medical supervision and the dose monitored by a medical professional.

Dextroamphetamine and Pemoline

These two medications can be found under the names of Dexedrine® and Cylert®.
They are both stimulants but given to hyperactive children have the effect of calming them down.

Docosahexaenoic Acid (DHA)

There has been research undertaken looking at the effect of fish oils, in particular DHA, and
childrens concentration levels. This led to a number of schools in the United Kingdom performing a trial.
The results showed that upto 60% of pupils had a noticeable improvement in their concentration and behavior also improved in those children involved in the trial.
Having read about the trial we tried Andrew on Salmon Oil capsules as these contained a high level of DHA and thought that there was some improvement in his behavior. However, we tried 'Haliborange High DHA Concentration + Vitamins A+C+D+E' and this made a huge difference after about 3 weeks and is still working along with the Methylphenidate.