Depends on how long he has been doing the drugs
I have listened to Rush on my car radio at least every week or two for over 10 years and the only change I ever noted was when he went deaf. That was quite obvious even before he admitted the problem.
I am sure that a ten year old broadcast would be different in the way that a cartoon character changes over time in unnoticeable ways but the message and the basic delivery have been the same over the long haul.