No, it is primarily the opiates which cause constipation. I have had a problem all of my life, possibly related to CMT (hereditary neuropathy), which caused severe fissures, and compounded now by MSContin and Percocet, but miralax or generic polyethylene glycol works fine for me. One problem solved! (two actually, since the pain meds are working as well). I have not heard of gabapentin causing constipation, I am on it as well and it has not affected my bowels. If you don't currently have a problem I am pretty sure that you won't.