药理学讲义07-Cholinergic-Antagonists

Chapter7CholinergicAntagonists胆碱受体阻断药2Ganglion-BlockingAgentsNicotinicreceptorsintheautonomicgangliadifferfromnicotinicreceptorsattheneuromuscularjunction,allowingfortheuseofspecificdrugsNeuromuscularblockershavebeendiscussedpreviouslyGanglionicblockersprobablyactbybindingontheionchannels.Resultsarecomplexandunpredictable,asboththeortho-andparasympatheticsystemsareinhibitedNicotinefirststimulates,theninhibitsganglionictransmissions.Bloodpressureandheartrateareincreased.ItisalsoaCNSstimulantTrimetaphanisusedforemergencyloweringofbloodpressure,inIVinfusion3Trimetaphan樟磺咪芬Trimetaphanisashort-actingganglionicblockeradministeredbyIVinfusion,foremergencyloweringofbloodpressureItisusedincaseofpulmonaryedemaassociatedwithhighbloodpressure(Whynotuseab-blockerlikelabetalolinthiscase?)4MuscarinicAntagonistsThiotropiumandipratropiumarediscussedinthechapteronrespiratorydrugsOtherwise,antagonistsofmuscarinicreceptorshavelimiteduses,totheexceptionofatropineandscopolamine5Atropine阿托品AtropineisanalkaloidextractedfromAtropabelladona.ItinhibitsmuscarinicfunctionsItsuseislimitedtothedilationofthepupil,forexaminationoftheretinaAdministrationisineyedrops.Glaucomaisacontraindication6Scopolamine东莨菪碱Scopolamineisanotherbelladonaalkaloid,thathasalongerdurationofaction.ItisusedtocontrolnauseainmotionsicknessOraldosageis125to500micrograms4to6timesadayforteenagersandadults,butitmayaswellbeadministeredinatransdermalpatchAdverseeffectsareasummaryofanticholinergiceffects:constipation,drymouth,blurredvision,confusion,urinaryretentionContra-indicationsareprostateenlargement,closed-angleglaucoma,gastricreflux,atonicintestine7ScopolamineButylbromide丁溴东莨菪碱Scopolaminebutylbromideisusedtorelieveintestinalspasm,suchasinchronicinflammatoryboweldiseaseOraldosageis10mguptothreetimesadayAdverseeffectsaresimilartothoseofscopolamineConfusionwithscopolamineisafrequentcauseofaccidents8AdditionalQuestionsWhyisnicotinedangerousforpatientssufferingfromanginapectoris?Atropine,scopolamineandbenztropinehaveactionsintheCNS,butnotsomuchipratropiumbromide.Anyideawhy?