COX II Inhibitors

CLASS

  • Selective COX-2 inhibitors

Types

  • celecoxib
  • parecoxib
  • rofecoxib
  • valdecoxib
  • also known as coxibs

MECHANISM OF ACTION

  • developed to try and inhibit prostacyclin synthesis by the COX-2 isoenzyme induced at sites of inflammation without affecting the action of the constitutively active COX-1 isoenzyme found in gastic mucosa, platelets & kidney.
  • have fewer GI side effects
  • no impact on platelet function
  • COX-2 is constitutively active in kidneys -> still produce the renal toxicities

INDICATIONS

  1. anti-inflammatory – OA, RA, familial adenomatous polyposis, gout, ankylosing spondylitis
  2. anti-pyretic
  3. analgesic – dysmenorrhoea, acute musculoskeletal pain, post op pain

ADVERSE EFFECTS

  • no effect on platelet aggregation, bleeding time & post-op blood loss.
  • bone healing attenuated
  • interactions: aspirin -> increases GI haemorrhage, warfarin -> increases INR, K+ sparring diuretics -> increase K+
  • ? increase in CVA & IHD events
  • increase in incidence of CHF
  • hypertension
  • liver dysfunction can take place
  • same renal risks as non-selective NSAIDs

PHARMACOKINETICS

  • Absorption – highly lipophilic
  • Distribution
  • Metabolism – hepatic
  • Elimination –

EVIDENCE

  • -> COX 2 inhibitors and NSAIDS have similar effects on renal function
  • -> COX 2 inhibitors don’t produce bronchospasm in aspirin induced respiratory disease
  • -> COX 2 inhibitors -> no effect of platelet function
  • -> COX 2 inhibitors -> same peptic ulcer rate as placebo (decreased compared to NSAIDS)
  • -> COX 2 inhibitors -> don’t give in patients with lots of vascular risk factors
  • -> parocoxib & valdecoxib DO NOT increase risk of cardiovascular disease after non-cardiac surgery
  • -> COX 2 inhibitors and NSAIDS are associated with the same rates of adverse CVS effects (MI)
  • -> short-term use of COX 2 inhibitors do not affect bone healing after spinal fusion
  • -> VIGOR study looked @ rofecoxib vs naproxen and found significant increase in MI in rofecoxib group (patients on low-dose aspirin were excluded)

PROS AND CONS

Advantages

  • less GI side-effects (dyspepsia, ulcers and GI bleeding) – although this point has been challenged
  • NICE recommendation of COX 2 use in individuals with high risk of GIH (2000)
  • opioid sparing actions

Disadvantages

  • increase in vascular morbidity (CVA, MI, IHD) – rofecoxib (VIGOR study)
  • more expensive
  • same adverse effect on platelets
  • contra-indicated in peri-operative patient with the following: previous MI or CVA, cardiac or vascular surgery, patient at high risk of vascular disease undergoing major surgery (MEDSAFE statement, 2005)
  • Na+ and K+ retention (effect on renal PG synthesis)
  • nephrotoxic
  • increased risk of thrombosis (reduced platelet prostacyclin without change in thromboxane)
  • hypertension
  • pregnancy -> premature closure of ductus arteriosus -> intrauterine foetal death
  • interacts with warfarin (increased risk of bleeding and increased INR)

CCC Pharmacology Series

Critical Care

Compendium

Chris is an Intensivist and ECMO specialist at The Alfred ICU, where he is Deputy Director (Education). He is a Clinical Adjunct Associate Professor at Monash University, the Lead for the  Clinician Educator Incubator programme, and a CICM First Part Examiner.

He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives. He was one of the founders of the FOAM movement (Free Open-Access Medical education) has been recognised for his contributions to education with awards from ANZICS, ANZAHPE, and ACEM.

His one great achievement is being the father of three amazing children.

On Bluesky, he is @precordialthump.bsky.social and on the site that Elon has screwed up, he is @precordialthump.

| INTENSIVE | RAGE | Resuscitology | SMACC

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