Many of the warnings on prescription inserts - are in compliance with possible future litigation and are not necessarily going to be the outcome of a medication....
Ariadne - if your ten year old was prescribed such a drug for migraines....did the doctor do a thorough physical check up prior to recommending anything?
A history of the onset of the migraines - certain allergies to certain foods can set them off - eyesight impairment - lack of ability to focus - especially when they are deeply involved in schoolwork, computer, and classroom chalkboard reading.... terrible light sensitivity is often never picked up and some children have a terrible time with changing light patterns such as a sudden burst of sunlight from behind clouds...this can tick off a headache so badly.... just plain anxiety over a party or a school test.... or blood sugar irregularities..... even a spider bite...or worse a child your son is having to deal with at school such as a bully or a highly competitive one your child does not get along with.
Allergy tests would be the first with a regular eye chart exam and hearing and also teeth eruption- with the molars especially.... tonsils, and all the regular childhood stuff.
I am not writing this in the assumption it hasn't been done, but what does your doctor base the son's migraine onset upon? Has he given you the reasons for prescribing the medication? What is it supposed to do for your child? Is it a temorary fix, a cautionary trial, or a permanent part of your son's future life?
It must be a nightmare for families choosing among all of the offerings placed before them, whether to work, whether to stay home, whether to go to a doctor or try some home remedy, and it could take quite a while to pin down what the problem is..... but rather than the quick fix, I'd take parental
investigation along with a bit of an "old fashioned doc"....for a while....before introduction of anything medicinal prescribed on a regular basis.... which may (or not) set up another set of symptoms.