<prompt> Anti-parkinsonism drug that is selective COMT inhibitor?EntacaponeRopinirolePergolidePramipexole  <response>: Ans. a Entacapone Ref. KDT 6thpg. 415ADRENERGIC DRUGSSr NoStepsiteActionDrugResponse1.Synthesis of NAInhibition Utilization of same synthetic pathwaya-methyl-p-tyrosine a-methyl dopaDepletion of NAReplacement of NA by a-methyl NAfalse transmitter2.Axonal uptakeBlockadeCocaine, desipra- mine, guanethidine, antihistaminics, ephedrinePotentiation of NA endo- and exogenous, inhibition of tyramine3.Granular uptakeBlockadeReserpineDepletion of NA degraded by MAO4.Nerve impulse coupled release of NAInhibitionGuanethidine, bretyliumLoss of transmission5.Granular NADisplacementGuanethidineInitially sympathomimetic, depletion later.6.Membrane NA poolExchange diffusionTyramine, ephedrineIndirect sympathomimetic7.MetabolismMAO inhibition COMT inhibitionNialamid tranylcy- promine Tolcapone, entacaponePotentiation of NA slight, Of tyramine marked Potentiation of NA slight8.ReceptorsMimickingPhenylephrine Clonidinea1 sympathomimetica2-inhibition of NA release, sympathetic outflow IsoprenaiineSalbutamolb1 b2 - sympathomimeticb2-sympathomimetic BlockadePhenoxybenzaminePrazosinYohimbinePropranololMetoprolola1 a2 - blockadea1- blockadea2 - blockadeb1 b2 - blockadeb1 - blockadePergolidePergolide, another ergot derivative, directly stimulates both D1 and D2 receptors.It too has been widely used for parkinsonism, and comparative studies suggest that it is more effective than bromocriptine in relieving the symptoms and signs of parkinsonism, increasing on-time among response fluctuators, and permitting the levodopa dose to be reduced.PramipexolePramipexole, which is not an ergot derivative, has preferential affinity for the D3 family of receptors. It is effective when used as monotherapy for mild parkinsonism.RopiniroleRopinirole, another nonergoline derivative, is a relatively pure D2 receptor agonist that is effective as monotherapy in patients with mild disease and as a means of smoothing the response to levodopa in patients with more advanced disease and response fluctuations.RasagilineRasagiline, another monoamine oxidase B inhibitor, is more potent than selegiline in preventing MPTP- induced parkinsonism and is currently under study as a neuroprotective agent.TolcaponeSelective COMT inhibitors such as tolcapone and entacapone also prolong the action of levodopa by diminishing its peripheral metabolism. 