All the following drugs are reversible inhibitors of COX EXCEPT:
ANSWER: (C) AspirinREF: http://en.wikipedia.org/lviki/Cyclooxygenase, KDT 6th edition, Katzung 9th edition, Goodman Gillman manual of pharmacology and therapeutics 2008 editionRepeat from June 2010 pharmacologyMECHANISM OF ACTION OF ASPIRIN:Non-steroidal anti-inflammatory drugs (NSAIDs), such as aspirin and derivatives of ibuprofen, inhibit cyclooxygenase activity of PGH2 Synthase. There are two isoforms of PGH2 Synthase: COX-1 8c COX-2 (Cyclooxygenase 1 & 2)Aspirin's ability to suppress the production of prostaglandins and thromboxanes is due to its non-competitive irreversible inactivation of the cyclooxygenase (COX1 & COX2) enzyme. Cyclooxygenase is required for prostaglandin and thromboxane synthesis. Aspirin acts as an acetylating agent where an acetyl group is covalently attached to a serine residue in the active site of the COX enzyme. This makes aspirin different from other NSAIDs (such as diclofenac and ibuprofen), which are competitive reversible inhibitorsCYCLOXYGENASE: COX1COX 2ALSO KNOWN AS EXPRESSIONPGFF synthase 1Always present, in all normaltissuesPGH-, synthase 2Inducible at the site of inflammation (normally very low? levels) plus normally in brain & kidneySTIMULUSINCREASE ON STIMULUS FUNCTIONHumoral stimulation2-4 foldsHousekeeping; e.g. Gastric cytoprotection, Ductus arteriosus patencyCytokines, growth factors, tumor promoters10-20 foldsInflammatory
Diclofenac
Ibuprofen
Aspirin
Indomethacin
Prostaglandins