Prospective evaluation of parkinsonism and tremor in patients treated with valproate.

We observed a high incidence of postural and intentional tremor in patients exposed to VPA, although not strong enough to interfere with normal life. l-dopa unresponsive parkinsonism was recorded in 10% of patients who received VPA treatment. No correlation with gender, dosage, duration of treatment or concomitant administration of other antiepileptic drugs was observed. The mechanisms for such side effects are unclear. As new GABA mimetic drugs have been postulated to be useful in tremor control [8], it remains paradoxical that VPA should exacerbate such symptomatology by means of a similar mechanism of action.