Methods of treatment using a gastric retained gabapentin dosage form

A method for treating a subject diagnosed with epilepsy, psychiatric disorders, neuropathic pain or movement disorder, comprising

• administering to the subject an extended release oral dosage form comprising an osmotic device comprising a core comprising gabapentin and a semipermeable membrane surrounding the core, wherein the semipermeable membrane comprises a plasticizer, is permeable to a fluid in an environment of use and is substantially impermeable to unsolubilized gabapentin,
• wherein the oral dosage form as formulated is of sufficient size to promote retention in the stomach of the subject in the fed mode for a period of at least 5 hours, and
• wherein the gabapentin is released into the upper gastrointestinal tract over a period of about 5-12 hours at a rate sufficient to achieve a lower maximum plasma concentration (Cmax) compared to an equal dose of gabapentin provided by an immediate release dosage form.