Because gabapentin has a Tmax of 3 to 31/2 hours and T1/2 of 5 to 9 hours it is less likely to improve sleep onset when taken at bedtime (thus, not helpful for sleep-initiating insomnia). It may help to deal with sleep maintenance insomnia in patients with pain, because of its efficacy in the treatment of pain disorders. As it is eliminated by kidney, renal function expected to affect clearance (potential side effects next day can be significant).