Can Gabapentin, 100 mg twice a day, cause a pink rash across one s back? Painfull Rash patch @ one inch high & two in. Long, made up of very pink bumps @ 1/16 inch diameter with a space of @ 1/8 between bumps. Random spacing. There are 3 of these patches on a 5 degree diagonal across just above the pelvic plate, high on right, even with plate on left.