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).1 It 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 (Item No. 13248) and carbidopa (Item No. 23783), 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.2 In a 6-OHDA rat model of Parkinson’s disease, entacapone (10 mg/kg), in combination with L-DOPA and benserazide (Item No. 20298), increases contralateral turning behavior and striatal extracellular dopamine levels.3 Entacapone also inhibits contraction of colon longitudinal muscle explants from a 6-OHDA rat model of Parkinson’s disease (EC50 = 200 µM).4 Formulations containing entacapone have been used in the treatment of Parkinson’s disease.WARNING This product is not for human or veterinary use.