Entacapone-d₁₀is intended for use as an internal standard for the quantification of entacapone by GC- or LC-MS. Entacapone is a reversible catechol O-methyltransferase (COMT) inhibitor (IC₅₀s = 10, 10, 20, and 160 nM for rat duodenum, brain, erythrocyte, and liver COMT, respectively).¹It is selective for COMT over monoamine oxidase A (MAO-A) and MAO-B and phenolsulphotransferase M (PST-M) and PST-P (IC₅₀s = >50 µM). Entacapone (10 mg/kg), in combination with L-DOPA and carbidopa , reduces 3-O-methyldopa (3-OMD) levels in the rat striatum and hypothalamus to 52 and 27%, respectively, of the levels in control animals receiving only L-DOPA and carbidopa.²In a 6-OHDA rat model of Parkinson's disease, entacapone (10 mg/kg), in combination with L-DOPA and benserazide , increases contralateral turning behavior and striatal extracellular dopamine levels.³Entacapone also inhibits contraction of colon longitudinal muscle explants from a 6-OHDA rat model of Parkinson's disease (EC₅₀= 200 µM).⁴Formulations containing entacapone have been used in the treatment of Parkinson's disease.

1.Nissinen, E., LindÉn, I.B., Schultz, E., et al.Biochemical and pharmacological properties of a peripherally acting catechol-O-methyltransferase inhibitor entacaponeNaunyn Schmiedebergs Arch. Pharmacol.346(3)262-266(1992) 2.MÄnnistÖ, P.T., Tuomainen, P., and Tuominen, R.K.Different in vivo properties of three new inhibitors of catechol O-methyltransferase in the ratBr. J. Pharmacol.105(3)569-574(1992) 3.Gerlach, M., van den Buuse, M., Blaha, C., et al.Entacapone increases and prolongs the central effects of L-DOPA in the 6-hydroxydopamine-lesioned ratNaunyn Schmiedebergs Arch. Pharmacol.370(5)388-394(2004) 4.Li, L.-S., Liu, C.-Z., Xu, J.-D., et al.Effect of entacapone on colon motility and ion transport in a rat model of Parkinson's diseaseWorld J. Gastroenterol.21(12)3509-3518(2015)