Meloxicam
Meloxicam. Enolic-acid NSAID — preferential COX-2 inhibitor at low doses (lower GI bleed signal than non-selective NSAIDs). Long half-life… Oral half-life 20 h.
Enolic-acid NSAID — preferential COX-2 inhibitor at low doses (lower GI bleed signal than non-selective NSAIDs). Long half-life supports once-daily dosing. CYP2C9 substrate.
PK: the cited study is a two-tablet bioequivalence with no intravenous arm, so it could not yield an absolute bioavailability and states no volume at all. Its half-life of 13.7 h is verbatim but is an ORAL TERMINAL value, and it conflicts with the 78-volunteer study that did include intravenous and rectal arms and reports "an elimination half-life (t1/2) of around 20 h". V 13.9 L is DERIVED from that same paper clearance of 7 to 8 ml/min and its half-life, and is flagged as such; because that dataset includes intravenous dosing it is a true volume. NOTE IN THE RECORD DEFENCE: a small volume is CORRECT in principle here — meloxicam is more than 99.5% protein bound, so a value near 12 to 14 L is the expected consequence of confinement to plasma and interstitial water, not a contradiction. So the stored 11 L was unsourced rather than absurd. F is set to 1 on the qualitative "almost complete absorption over a prolonged phase". THE EFFECT SITE IS SYNOVIAL FLUID, not plasma, at a fairly constant ratio near 0.47, and free synovial concentration exceeds the enzyme inhibitory concentration from 6 to 36 hours. The intramuscular route is removed as unparameterised.
Pharmacokinetics
- Oral — t½ 20 h · F 100% · Vd 13.9 L
- IV — t½ 20 h · F 100% · Vd 13.9 L
Sources: PMID:11874389, PMID:9105543, PMID:11108435