Preferential COX2 Inhibitors

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Chapter: Essential pharmacology : Nonsteroidal Anti-inflammatory Drugs And Antipyreticanalgesics

Nimesulide : This newer NSAID is a relatively weak inhibitor of PG synthesis and there is some evidence to indicate relative COX2 selectivity. Anti-inflammatory action may be exerted by other mechanisms as well, e.g. reduced generation of superoxide by neutrophils, inhibition of PAF synthesis and TNFα release, free radical scavanging, inhibition of metalloproteinase activity in cartilage.


PREFERENTIAL COX2 INHIBITORS

 

Nimesulide

 

This newer NSAID is a relatively weak inhibitor of PG synthesis and there is some evidence to indicate relative COX2 selectivity. Anti-inflammatory action may be exerted by other mechanisms as well, e.g. reduced generation of superoxide by neutrophils, inhibition of PAF synthesis and TNFα release, free radical scavanging, inhibition of metalloproteinase activity in cartilage. The analgesic, antipyretic and anti-inflammatory activity of nimesulide has been rated comparable to other NSAIDs. It has been used primarily for shortlasting painful inflammatory conditions like sports injuries, sinusitis and other earnosethroat disorders, dental surgery, bursitis, low backache, dysmenorrhoea, postoperative pain, osteoarthritis and for fever.

 

Nimesulide is almost completely absorbed orally, 99% plasma protein bound, extensively metabolized and excreted mainly in urine with a t½ of 2–5 hours.

 

Adverse effects of nimesulide are gastrointestinal (epigastralgia, heart burn, nausea, loose motions), dermatological (rash, pruritus) and central (somnolence, dizziness). Gastric tolerability of nimesulide is better, though an Italian study has shown that ulcer complications are as prevalent as with other NSAIDs. There is also no proof that renal complications are missing: hematuria is reported in few children. Instances of fulminant hepatic failure have been associated with nimesulide and it has been withdrawn in Spain and Turkey; use in children is banned in Portugal and Israel. However, a Finish committee for proprietary medicinal products has concluded that hepatic reactions to nimesulide are similar to other NSAIDs. Considering that it has not been marketed in many countries like the UK, USA, Australia, Canada, the overall safety of this drug, especially in children, has been questioned. However, most asthmatics and those who develop bronchospasm or intolerance to aspirin and other NSAIDs do not cross react with nimesulide. Its specific usefulness appears to be only in such patients.

 

Dose: 100 mg BD; NIMULID, NIMEGESIC, NIMODOL 100 mg tab, 50 mg/5 ml susp.

 

Meloxicam

 

This newer congener of piroxicam has a COX2/COX1 selectivity ratio of about 10. Since measurable inhibition of platelet TXA2 production (a COX1 function) occurs at therapeutic doses of meloxicam, it has been labelled ‘preferential COX2 inhibitor’. Efficacy of meloxicam in osteo and rheumatoid arthritis is comparable to piroxicam. In shortterm studies, gastric changes with the lower dose (7.5 mg/day) were found to be similar to placebo, but at the higher dose (15 mg/day) they were intermediate between placebo and piroxicam. Gastric side effects of meloxicam are milder, but ulcer complications (bleeding, perforation) have been reported on longterm use. Thus, there is no convincing evidence that meloxicam is safer than other NSAIDs.

 

Dose: 7.5–15 mg OD; MELFLAM, MELOD, MUVIK, MCAM 7.5 mg, 15 mg tabs.

 

Nabumetone

 

It is a prodrug—generates an active metabolite (6MNA), and is a relatively more potent COX2 than COX1 inhibitor. It possesses analgesic, antipyretic and anti-inflammatory activities; effective in the treatment of rheumatoid and osteoarthritis as well as soft tissue injury. Nabumetone has caused a lower incidence of gastric erosions, ulcers and bleeding, probably because the active COX inhibitor is produced in tissues after absorption. However, abdominal cramps and diarrhoea can occur and there is no firm evidence of its relative safety compared to traditional NSAIDs.

 

NABUFLAM 500 mg tab; 1 tab OD.

 

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