I'm not sure if this will be of any interest to anyone else or is common knowledge but I received the following note from the DVLA.
"If you are currently being treated with or start with Selegiline please be aware that if you are tested by police for drugs or accused of drug driving and are asked by police if you are taking any medication, you should declare your use of prescribed Selegiline. You may also need to provide the police with anything you have that would confirm this, such as medication if you have it with you or a prescription, counterfoil or any medical letter, report or advice."
I'm not taking any drugs at the moment so I'm not sure if Selegline is a common drug or not. I was a little surprised at receiving the note though.