Valproic acid as an adjuvant analgesic: adult Fanconi syndrome.

We report an 80-year-old woman who developed severe hypophosphataemia and elevated urinary phosphate levels while started on valproic acid. This occurred within 1-2 days of starting valproic acid. There are rare single-patient reports of the association of valproic acid with adult Fanconi syndrome. This generally occurs after long-term exposure to valproate. This is the first reported experience of Fanconi's syndrome in an adult with acute exposure to valproic acid. Clinicians should be aware of the possible association.