Nitrous oxide "whippit" abuse presenting with cobalamin responsive psychosis.

INTRODUCTION: Nitrous oxide is a commonly abused inhalant drug. It is known to precipitate vitamin B12 deficiency when used chronically and acutely, especially in people having marginal vitamin B12 reserve. CASE REPORT: We are presenting a case of nitrous oxide "whippit" abuse in a thirty-three-year-old male with bizarre behavior and delusions. The patient had low normal levels of vitamin B12 (202 pg/ml), but he had markedly high methylmalonyl CoA (1078 nmol/L) and homocysteine (48.4 mcmol/L). Treatment with intramuscular cobalamin led to a resolution of his psychosis. DISCUSSION: This case report highlights the need to consider vitamin B12 deficiency in patients who arrive at a hospital with psychiatric manifestations and who report having a history of nitrous oxide exposure or abuse in the recent or remote past. A review of the literature on the neuropsychological manifestations of vitamin B12 deficiency is provided.