Adult taking Ritalin | ADHD Information

My husband has ADHD and, after seeing our son's positive reaction to Ritalin, would like to start taking it himself.  We are wondering whether there are adults who take it on an "as needed" basis, like to make it through meetings, etc.  DH is very high-functioning and extremely creative but has some of the negatives that go with ADHD, too, like having to be on-the-go constantly, not finishing things, being in his own little world, getting edgy and having a short fuse at times.  The other day the receptionists at his workplace told me that he is the hardest person to find because he is "always running around " and "hyper".  They told me that they don't let him drink Red Bull , which he likes to do (probably self medicating, actually).  Lucky for him, he has a very high IQ and is so creative that he never has been in danger of losing his job, but he can hardly make it through meetings.

Our son is on Daytrana and really needs it to get through his day at all, but my husband would like to take it just when he needs to focus and deal with meetings and paperwork.  Does anyone else do this?  Is it safe for an adult heart to go on and off like this?  Any other ideas?