Gabapentin gabantin 300mg is a prescription medicine. It comes as an oral capsule, an immediate-release oral tablet, an extended-release oral tablet, and an oral solution. Gabapentin gabantin 100mg tablet is available as the brand-name drug Neurontin. It’s also available as a generic drug. Generic drugs usually cost less than the brand-name version. In some cases, the brand-name drug and the generic version may be available in different forms and strengths.