I don't think they'll HURT you, but I also think that they're not really going to help you all that much with your weight loss, at least no more than taking a regular multivitamin would.
I myself have bought the One A Day Weight Smart vitamins - I usually buy the One A Day Women's Multi, but once Safeway had all the One A Days on sale so I figured I might as well try the Weight Smart ones, which are usually priced a tad higher than the One a Day Women's.
I didn't feel anything different - didn't expect to though, even though there is caffiene powder in Weight Smart, per the One A Day website.
So I don't think they'll HURT you to take them - of course you'll have to ask your doc to verify that statement. It's just a multi with some caffiene added.