That said, Neurontin has an elimination half-life of 5-7 hours, if you have healthy kidneys. That means that half of the drug will be gone from your system in 7 hours, 75% gone in 14 hours, 87.5% gone in 21 hours, etc. As far as I know, commercial drug tests do not routinely screen for Neurontin and I don't believe there is any cross-reactivity with controlled substances.