Carbidopa-d3 is intended for use as an internal standard for the quantification of carbidopa by GC- or LC-MS. Carbidopa is a peripherally restricted inhibitor of dopamine decarboxylase, the enzyme that converts L-DOPA to dopamine.1 Administration of carbidopa (100 mg/kg) prior to administration of L-DOPA in dogs increases the plasma concentration of L-DOPA by 186% and prolongs the half-life in plasma by 48% and skeletal muscle extracellular fluid by 66%.2 Carbidopa also binds to and potentiates the activity of the aryl hydrocarbon receptor (AhR).3 It inhibits the proliferation of pancreatic cancer cells in vitro and tumor growth in vivo. Formulations containing carbidopa are used in combination with L-DOPA in the treatment of Parkinson’s disease to increase the amount of dopamine in the brain and reduce peripheral side effects associated with L-DOPA administration.
1.Clark, W.G., Oldendorf, W.H., and Dewhurst, W.G.Blood-brain barrier to carbidopa (MK-486) and Ro 4-4602, peripheral dopa decarboxylase inhibitorsJ. Pharm. Pharmacol.25(5)416-418(1973) 2.Deleu, D., Sarre, S., Ebinger, G., et al.The effect of carbidopa on the pharmacokinetics and metabolism of intravenously administered levodopa in blood plasma and skeletal muscleNaunyn Schmiedebergs Arch. Pharmacol.348(6)576-581(1993) 3.Ogura, J., Miyauchi, S., Shimono, K., et al.Carbidopa is an activator of aryl hydrocarbon receptor with potential for cancer therapyBiochem J.474(20)3391-3402(2017)