14 year old - OCD/Apergers - "forgetting" medication

Not impressed I must admit but thats my son to a tee. Goes with the flow, expects things to bend the way he wants etc and will make zero effort to help himself.

We've spent over £500 on private consultant appointments to get him seen and presribed medication. Found out for the last 10 days hes "forgotten" to take it.

Hes almost 15 - I'm absolately bomping mad with him. Surely, at 14/15 he should be able to know the importance of it?