Celecoxib - IRreversible, not reversible

[Phloston]

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P. 430 of FA2012 says COX-2 inhibitors (celecoxib) "reversibly inhibit specifically the cyclooxygenase (COX) isoform 2..."

The Lange pharmacology cards say (on card #170) "Celecoxib irreversibly inhibits COX2..."

So I went to PubMed.

Biochem J. 2001 Aug 1;357(Pt 3):709-18.
A three-step kinetic mechanism for selective inhibition of cyclo-oxygenase-2 by diarylheterocyclic inhibitors.
Walker MC, Kurumbail RG, Kiefer JR, Moreland KT, Koboldt CM, Isakson PC, Seibert K, Gierse JK.

That article discusses the three-step inhibition mechanism of selective COX2 inhibitors, that, despite demonstrating a reversible COX1-inhibitory component, demonstrates selective COX2 inhibition that is irreversible (keeping in mind that celecoxib is mostly COX2 inhibition).

In terms of the USMLE, they're probably just interested that we know that aspirin is irreversible, but FA should say "irreversible," not "reversible," for celexocib.

 

[JRjcu08]

Several other papers (see below-dated later than the one you referenced) state otherwise... (that celecoxib is reversible). Lippincott Pharm also says time dependent and reversible. But as you said, the take home is that aspirin is irreversible, and that celecoxib is COX-2 specific.

Molecular Pharmacology April 1, 2003 vol. 63 no. 4 870-877
Characterization of Celecoxib and Valdecoxib Binding to Cyclooxygenase
William F. Hood, James K. Gierse, Peter C. Isakson, James R. Kiefer, Ravi G. Kurumbail, Karen Seibert and Joseph B. Monahan


Pharmacol Res. 2006 Aug;54(2):77-84.
Reversible binding of celecoxib and valdecoxib with human serum albumin using fluorescence spectroscopic technique.
Seedher N, Bhatia S.
   



 

[DroptheBop]

The first aid entry also indicates that it "spares COX-1" which is apparently untrue.

Interesting following study on celecoxib and its use with aspirin.

"Consistent with previous studies (24), we found that celecoxib is more effective in causing instantaneous inhibition of COX-1 than COX-2 (IC50 values of 8.3 μM vs. 15 μM for COX-1 and COX-2, respectively) (Fig. S1). We also confirmed that, unlike the situation with COX-2, celecoxib is a freely reversible, competitive inhibitor of COX-1 (24). The fact that celecoxib is a freely reversible inhibitor of COX-1 suggests that celecoxib must bind to both monomers of COX-1 to cause enzyme inhibition (10). "

Coxibs interfere with the action of aspirin by binding tightly to one monomer of cyclooxygenase-1.
Rimon G, Sidhu RS, Lauver DA, Lee JY, Sharma NP, Yuan C, Frieler RA, Trievel RC, Lucchesi BR, Smith WL. Proc Natl Acad Sci U S A. 2010 Jan 5;107(1):28-33. Epub 2009 Dec 1.

Source Department of Biological Chemistry, University of Michigan, Ann Arbor, MI 4810, USA.

http://www.pnas.org/content/107/1/28.full.pdf+html