Warden Wolfe poisons Barry to make him pass out. It's previously been established that because of Barry's super fast metabolism any drug, including alcohol and pain killers, have very little effect on him and do not last long. It's unlikely that Warden Wolfe would have accounted for Barry's metabolism when he drugged him so if it had any effect at all it most likely would have only lasted for a few seconds.
Barry notes his dad was falsely imprisoned for 17 years however in The Man Who Saved Central City (2015) he got exonerated sometime in late November 2015 meaning Henry spent 15 years and 8 months in Iron Heights.