Enzyme inhibited in cyanide poisoning?
Correct Answer: Cytochrome oxidase
Description: Ans. a (Cytochrome oxidase). (Ref. Harrison, Principles of Medicine, 18th/Ch. 35, 222)CYANIDE TOXICITY# Cyanide binds irreversibly to Cytochrome a/a3 (Complex IV) & this inhibits ETC.# Cyanide poisoning inhibits mitochondrial cytochrome oxidase -blocks electron transpot - prevents O2 utilization and oxidative metabolism# Cyanide poisoning during nitroprusside therapy can be prevented by prophylactic mechanism of thiosulphate.# Treatment: High dose O2, amyl nitrate inhalation, sodium nitrate, sodium thiosulphate, hydroxycobalalmine. PoisoningEnzyme involved1COCytochrome oxidase2Cardiac glycosidesSodium potassium ATPase3Hydrogen sulphideCytochrome oxidase4INHGlutamic acid decarboxylase5LithiumAdenylate cyclase6NSAIDSCOX1 and COX2 (COX2 inducible)7OPPAcetyl choline esterase8Theophyline, caffeine (methyl xanthins)PhosphodiaesteraseEducational point:Uncouplers of oxidative phosphorylation:# 2, 4, Dinitrophenol;# Highdose Aspirin# ThermogeninAsphyxiants CYTOCHROME OXIDASE NHIBITORS Inhibition of mitochondrial cytochrome oxidase, thereby blocking electron transport and oxidative metabolism. Carbon monoxide also binds to hemoglobin and myoglobin and prevents oxygen binding, transport, and tissue uptake (binding to hemoglobin shifts the oxygen dissociation curve to the left).Signs and symptoms of hypoxia with initial physiologic stimulation and subsequent depression; lactic acidosis; normal PO2 and calculated oxygen saturation but decreased oxygen saturation by co-oximetry.Headache and nausea are common with carbon monoxide.Sudden collapse may occur with cyanide and hydrogen sulfide exposure.A bitter almond breath odor may be noted with cyanide ingestion, and hydrogen sulfide smells like rotten eggs.High-dose oxygen.Inhaled amyl nitrite and IV sodium nitrite and sodium thiosulfate (Lilly cyanide antidote kit) for coma, metabolic acidosis, and cardiovascular dysfunction in cyanide poisoning.Amyl and sodium nitrite (without thiosulfate) for similar toxicity in hydrogen sulfide poisoning.Hyperbaric oxygen for moderate to severe carbon monoxide poisoning and for cyanide or hydrogen sulfide poisoning nresponsive to other measures.- Carbon monoxide,- Cyanide,- Hydrogen sulfide
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