We describe a 38-year-old woman who developed symptoms of hallucinogen persisting perception disorder (HPPD) after using lysergic acid diethylamide (LSD) once and continued to have symptoms of HPPD for nearly 17 years, although she did not use LSD after her first use. The symptoms of HPPD were temporally related to her first LSD use and she responded well to risperidone within a few weeks of commencing on the same. Although different medications have been tried in the management of HPPD including risperidone, olanzapine, clonidine, fluoxetine, sertraline, benzodiazepines and anti-epileptic medications, none have been proven to be the definitive medication of choice in the treatment of HPPD. Furthermore, there have been case reports suggesting worsening of symptoms with risperidone; however, the response to risperidone in our patient suggests the possibility of its effectiveness in the management of HPPD symptoms in some patients.
