Gabapentin-Induced Ejaculatory Failure and Anorgasmia

Mr. A was a 41-year-old man with a long history of bipolar II disorder and alcohol dependence with intermittent cocaine abuse. After completing a 4-week alcohol treatment program, he developed mild hypomania. He had no medical problems and no history of sexual dysfunction. Gabapentin treatment was initiated for hypomania at 300 mg per day and gradually titrated to 600 mg 3 times per day over 1 month. While taking 300 mg of gabapentin 3 times per day, he noticed orgasm was more difficult to attain. Neither libido nor erection was affected. Gabapentin reduced his hypomania, but as the dose increased, he found ejaculation and orgasm increasingly difficult to achieve. He could have intercourse with a normal erection for 20 minutes but could not ejaculate. At times he attained a sense of incomplete orgasm sensation but did not ejaculate. There was no retrograde ejaculation. Mr. A took gabapentin for 4 months and eventually stopped the medication because of his inability to ejaculate. During this time, he remained abstinent from alcohol, and the results of three urine drug screens for cocaine and marijuana were negative. He denied using other illicit or over-the-counter drugs. One week after stopping the gabapentin dose, he reported the return of his usual orgasm and ejaculation abilities.