Carbidopa dosage modifies L-dopa induced side effects and blood levels of L-dopa and other amino acids in advanced parkinsonism

Acta Neurol Scand. 1985 Nov;72(5):506-11. doi: 10.1111/j.1600-0404.1985.tb00908.x.


Thirty-four patients with advanced Parkinson's disease showing intolerance to therapeutic doses of L-DOPA were treated with L-DOPA plus carbidopa at two different proportions. Ten patients preferred medication containing 10% carbidopa while 24 preferred 25% carbidopa. The increase of carbidopa reduced gastrointestinal disturbances and psychiatric side effects related to L-DOPA, but improvement of disability when measured according to objective tests was modest. Higher doses of carbidopa reduced peripheral DOPA metabolism and increased blood levels of tryptophan, 3-OM-DOPA and DOPA in relation to the administered dose.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Carbidopa / administration & dosage*
  • Drug Therapy, Combination
  • Female
  • Homovanillic Acid / blood
  • Humans
  • Kinetics
  • Levodopa / administration & dosage*
  • Levodopa / adverse effects
  • Levodopa / blood
  • Male
  • Middle Aged
  • Parkinson Disease / blood
  • Parkinson Disease / drug therapy*
  • Tryptophan / blood
  • Tyrosine / blood


  • Tyrosine
  • Levodopa
  • Tryptophan
  • Carbidopa
  • Homovanillic Acid