Mechanism of action<unk>  is a selective and reversible inhibitor of catechol-O-methyltransferase (COMT). COMT eliminates biologically active catechols present in catecholamines (dopamine, norepinephrine, and epinephrine) and their hydroxylated metabolites. When administered with a decarboxylase inhibitor, COMT acts as the major metabolizing enzyme for levodopa and metabolizes it to 3-methoxy-4-hydroxy-L-phenylalanine (3-OMD) in the brain and in the periphery. For the treatment of Parkinson's disease,<unk>  is given as an adjunct to levodopa and an aromatic amino acid decarboxylase inhibitor, carbidopa.<unk>  inhibits COMT in the periphery (but not, or at most marginally, in the brain) and the metabolism of levodopa, thus increasing plasma levels of levodopa and causing more constant dopaminergic stimulation in order to reduce the signs and symptoms presented in the disease. Pharmacokinetics Absorption The time to highest blood plasma concentrations is approximately one hour. The substance undergoes extensive first-pass metabolism. Absolute oral bioavailability (F) is 35%. Distribution The volume of distribution (Vd) after intravenous injection is approximately 20 liters. 98% of the circulating<unk>  is bound to serum albumin, which limits its distribution into tissues. Metabolism and elimination<unk>  is primarily metabolized to its glucuronide in the liver, and 5% are converted into the Z-isomer. It has a half-life of approximately 0.3–0.7 hours, with only 0.2% being excreted unchanged in the urine.
Entacapone
Rivastigmine
Influenzanet
Nabilone
Tasimelteon
Droxidopa
Ixabepilone
Zaleplon