first off, define opened...do you mean a needle was put through the rubber, or was the seal/rubber/everything taken off?
if you mean that some of the stuff has been pinned, but not all, and you wanna know if you can use the rest now...then most likely there are no large particles in the vial that can be filtered out...if anything, there could be some bacteria growth...so stick a pin in to vent and throw the vial in the oven...250 or so...then in the frig/freezer...do this hot/cold cycle several times and you should be good