I Have An Rx For Bentyl That Was Filled 12/17/14.

I have an Rx for Bentyl that was filled 12/17/14. The pharmacy puts a standard expiration date of one year past the date it was filled. I have no idea when this drug will/did actually expire. My question is, is Bentyl one of the drugs that becomes toxic past expiration date or can I take it with the only danger being it may be ineffective?