Gabapentin-induced Bilateral Lower Extremity Edema in a Patient with Pervasive Developmental Disorder and Schizoaffective Disorder

Gabapentin binds to the alpha-2-delta subunit of presynaptic voltage-gated calcium channels and is used for a wide variety of on- and off-label indications. Gabapentin is dosed at total daily doses ranging from 300 to 3600 mg/d, which is generally divided into 3 doses. Although gabapentin is generally well tolerated, 1 potential reported adverse effect is peripheral edema. However, due to the extensive number of etiologies of peripheral edema, medication causes may be overlooked on an inpatient psychiatric unit. This is a case of delayed identification of a probable adverse drug reaction to gabapentin (Naranjo score of 5) consisting of painful, 4+ pitting bilateral edema and a clear dose relationship in a patient with pervasive developmental disorder and schizoaffective disorder.