"As needed"

My wife finally got a prescription for Methylphenid 5mg.  It is a 5mg dose, which I assume is low to start of with and see how it works before building up.

The psychiatrist said she should take it "as needed."  She doesn't know what "as needed" means and has not taken it because she does not feel that she has needed it.  She is also worried about possible side effects.

My understanding of all psychiatric drugs is that you need to take them consistently for several weeks before you notice any results.  Also, you need to take a drug before you can decided if it works and if it causes side effects.

It seems like yet another dead end.

By the way, she lost her car key over a week ago and has been using my key to her car.  I can't use my car if hers is behind mine in the driveway.  If she takes my car, I am stranded because I can't use her car.  I have asked her to get a replacecement key, but she has not.  I keep asking me to send me information to handle an IRS problems since she has not gotten around to it, yet she never sends it to me!  How much more "as needed" does she need???