Though the bottle may not have any warnings, many brands do,even some OTC cold medicines do,much of these type supplements/weight loss agents can most definately trigger hypomania to a full blown manic episode.
It is always important to ask the doc first before using any other meds,even OTC stuff.
Stimulants,rather prescription,OTC, even natural herbs, are always asked to be avoided or check with your pdoc.
Some people with Bipolar may be able to take things in this class,while other can be negatively affected.
There are different variations of Bipolar,it's not a one size fits all, nor are the meds prescribed.
Example, those with Bipolar-I,can go from depressed to manic,even violent.
Bipolar-II,tend to have more severe depression but milder manic episodes,termed hypomanic.
Though stimulants can trigger either form of mania,BP-I would most likely be at risk of having explosive,manic episodes, while BP-II, not as severe.
That isn't set in stone either,cause again,everyone is not alike.
I wish you lots of luck, and hope you'll find a way to convince your son, to not use the stimulant and contact his pdoc.
Take care,
DE