Vitamin B6 Deficiency in Patients With Parkinson Disease Treated With Levodopa/Carbidopa

Clin Neuropharmacol. 2020 Sep/Oct;43(5):151-157. doi: 10.1097/WNF.0000000000000408.


Objective: The aim of the study was to investigate the role of L-DOPA/carbidopa (CD) therapy on vitamin B6 levels in patients with Parkinson disease (PD).

Methods: This is a cross-sectional retrospective study of vitamin B6 plasma levels in 24 patients with PD treated with L-DOPA/CD for 3 or more years, orally or intraduodenally. Vitamin B6 levels in plasma were measured by ELISA.

Results: All patients treated with intraduodenal L-DOPA/CD (6 of 6) and 13 of 18 patients receiving L-DOPA/CD orally had low plasma levels of vitamin B6. Eight of the 19 patients with low vitamin B6 levels had symptoms of hypovitaminosis B6. Patients with low vitamin B6 had been treated with larger doses of L-DOPA/CD, although the differences did not have statistical significance. Patients treated with intraduodenal L-DOPA/CD have vitamin B6 levels significantly lower than those treated with oral L-DOPA/CD. The variables that most correlated with vitamin B6 levels were the cumulative annual doses of CD (r = -0.36) and L-DOPA (r = -0.33) during the year preceding the study and the time to develop dyskinesias or fluctuations (r = +0.43).

Conclusions: Vitamin B6 could play an important role in PD and its levels seem to be influenced by L-DOPA/CD. Plasma vitamin B6 levels should be monitored in patients receiving high L-DOPA/CD doses, especially those treated with intraduodenal infusion.

MeSH terms

  • Aged
  • Aged, 80 and over
  • Antiparkinson Agents / adverse effects*
  • Antiparkinson Agents / therapeutic use
  • Carbidopa / administration & dosage
  • Carbidopa / adverse effects*
  • Carbidopa / therapeutic use
  • Cross-Sectional Studies
  • Drug Combinations
  • Duodenum
  • Dyskinesias / complications
  • Female
  • Folic Acid Deficiency / chemically induced
  • Humans
  • Infusions, Parenteral
  • Levodopa / administration & dosage
  • Levodopa / adverse effects*
  • Levodopa / therapeutic use
  • Male
  • Middle Aged
  • Parkinson Disease / complications*
  • Parkinson Disease / drug therapy*
  • Retrospective Studies
  • Vitamin B 12 Deficiency / chemically induced
  • Vitamin B 6 / blood
  • Vitamin B 6 Deficiency / chemically induced*
  • Vitamin B 6 Deficiency / complications*


  • Antiparkinson Agents
  • Drug Combinations
  • carbidopa, levodopa drug combination
  • Levodopa
  • Vitamin B 6
  • Carbidopa