Cough syrup Rx and drug test; how old is too "old"?

[Raven Sierra, BSN, RN]

This is kind of a bizarre question, but how long is a prescription "active" for drug-testing purposes?

Here's the situation: in December, I had bronchitis. The doctor prescribed cough syrup with codeine. I didn't use it all. Now I have another cold (maybe bronchitis again?) with a nasty, persistent cough, and I thought about taking some of the cough syrup to sleep last night. It's prescribed to me, and the prescription was filled on Dec. 2, 2015. But I didn't take it because I wasn't sure if it's still considered as a good prescription if I get drug-tested.

[TheCommuter, BSN, RN]

In most states, a prescription that is less than 12 months old is still considered valid. Therefore, a prescription medication that you obtained in December 2015 would not be 'too old' for most intents and purposes.