Gabapentin and gabapentin monohydrate.

Gabapentin [1-(amino­methyl)­cyclo­hexane­acetic acid, C9H17NO2] is a zwitterion in the solid state. Its crystal structure involves extensive hydrogen bonding between the NH3+ and COO− groups of neighboring mol­ecules. The structure of gabapentin monohydrate [1-(amino­methyl)­cyclo­hexane­acetic acid monohydrate, C9H17NO2·H2O] also involves such hydrogen bonding and, in addition, has a hydrogen-bonding network comprising the water mol­ecules and both the NH3+ and COO− groups.