The authors report the case of a severely retarded, 19-year-old female (treated with primidone 250 mg tid since age 12) who was admitted with visual and auditory hallucinations. After four days of continuing hallucinations, she went into classic catatonic schizophrenia. Upon examination, her primidone serum level was found to be well above the normal therapeutic range. The primidone dosage was decreased, and symptoms subsided as serum levels returned to normal.
