This 65-year-old woman with a 4-year history of PD and early dementia developed severe nausea and vomiting after a dose increase in levodopa to minimize episodes of off-related freezing of gait. At the emergency room, she was given promethazine (Phenergan), which had sufficient antiemetic effect to allow her discharge to home. While at home, she developed episodes of full-body flailing, which were captured by her husband on her cell phone and transmitted to us (the clip shown). The patient had to return to the emergency room, where administration of diphenhydramine (Benadryl) abated the complication.

This PD patient developed promethazine-induced acute dystonic reaction expressed as dramatic worsening of preexistent levodopa-induced dyskinesias. This patient was already functionally brittle given the presence of diphasic dyskinesias and freezing of gait in the “off” state alternating with tolerable peak-dose levodopa-induced dyskinesias in the “on” state, developing in the background of early dementia. Dyskinetic manifestations are exacerbated by promethazine and other phenothiazines. Prompt administration of drugs with anticholinergic properties is necessary to abort this iatrogenic complication.