TY - JOUR T1 - Benefit of folic acid supplementation in parkinsonian patients treated with levodopa JF - Journal of Neurology, Neurosurgery & Psychiatry JO - J Neurol Neurosurg Psychiatry SP - 549 LP - 549 DO - 10.1136/jnnp.74.4.549 VL - 74 IS - 4 AU - T Müller AU - D Woitalla AU - W Kuhn Y1 - 2003/04/01 UR - http://jnnp.bmj.com/content/74/4/549.1.abstract N2 - We read with interest the recent excellent review by Reynolds on the role of folic acid and the risks and benefits of its supplementation in the nervous system.1 It emphasises the beneficial importance of folate on the numerous methylation processes in combination with S-adenosylmethionine (SAM), which donates its methyl group to prevent hyperhomocysteinaemia.1 However SAM deficiency, which is associated with, for example, cognitive decline and/or mood disturbances, and increased total homocysteine levels, which support onset of vascular disease, may also caused by drugs, for example, levodopa.2,3 Levodopa is administered with dopa decarboxylase inhibitors (DDI) to prevent its peripheral degradation. This increases conversion of levodopa to 3-O-methyldopa (3-OMD) by the ubiquitious enzyme catechol-O-methyltransferase (COMT) in blood, peripheral tissues and in nigrostriatal neurons.2,3 COMT requires Mg2+ as cofactor and … ER -