Paediatric MS medication like Sativex or the forthcoming epilepsy medication Epidiolex contain mainly cannabidiol and a small amount of THC. The thing is THC isn't the big high from smoking weed, that actually comes from a Liver metabolite called 11-Hydroxy-THC.
The amounts of THC in the medication are small - in the case of Sativex it would take about 10 squirts to deliver the same amount of THC as your average edible - 12 squirts is the daily maximum spaced at intervals.
Since it's going right into your bloodstream via the nasal mucosa, the THC can't metabolise into 11-Hydroxy-THC in your Liver.
TL;DR CBD medication doesn't get you high. Marijuana sold as 'medicinal does', but that isn't the same thing.