source:
http://www.pharmacytimes.com/contributor/jeffrey-fudin/2015/09/how-gabapentin-differs-from-pregabalinHow Gabapentin Differs From PregabalinPregabalin is 6x stronger than Gabapentin.
an excerpt:
The bioavailability of generic gabapentin in tablet and capsule formulations equivalent to brand-name Neurontin is about 80% at lower doses such as 100 mg every 8 hours, but only 27% bioavailable at doses of 1600 mg every 8 hours.3,4 This differs greatly from pregabalin, which boasts a greater than 90% bioavailability across a dosage range from 75 mg to 900 mg daily in divided doses.