The BBC has an article about it too.
Canada limits caffeine content in beverages to 180 mg per serving. Prime and Celsius have 200 mg, this seems to be a relatively common amount for new drinks that are popping up in states. Prime, at least, is also not released in Canada yet, so any version out there is the stronger version.
I was surprised when I discovered the Canadian limits, in the states many drinks are 240 mg and some even 300 (always marketed as super extreme hardcore).