Objective: To study the influence of meloxicam, a cyclooxygenase-2 (COX-2)
preferential nonsteroidal antiinflammatory drug, on serum thromboxane and p
latelet function in healthy volunteers with use of the maximum recommended
daily dosage of 15 mg/day.
Methods: This study used an open, randomized crossover design. Indomethacin
(INN, indometacin) was given as a positive control for nonsteroidal anti-i
nflammatory drug-induced inhibition of platelet function. The following var
iables were recorded: thromboxane B-2 serum concentrations by radioimmunoas
say, platelet aggregation by whole blood aggregometry in response to collag
en 1.1 mu g/L and to arachidonic acid 0.35 mmol/L, and closure time with us
e of the PFA-100.
Results: Serum thromboxane B-2 at baseline was 535 +/- 233 nmol/L (mean +/-
SD) and was reduced for 95% by indomethacin to 26 +/- 19 nmol/L (P < .001)
and for 66% by meloxicam to 183 +/- 62 nmol/L (P < .001), Maximal platelet
aggregation in response to collagen at baseline was 18.7 +/- 1.6 ohms (Ome
ga). It was reduced by indomethacin to 7.3 +/- 4.5 Omega (P < .001), but no
t by meloxicam (19 +/- 2.5 Omega). Platelet aggregation in response to arac
hidonic acid at baseline was 12.2 +/- 2.0 Omega. It was reduced by indometh
acin in all subjects to 0 Omega, but not by meloxicam (11 +/- 2.4 Omega). C
losure time at baseline was 128 +/- 24 seconds and was prolonged by indomet
hacin to 286 +/- 38 seconds (P < .001), Meloxicam caused a minor prolongati
on of the closure time (141 +/- 32 seconds; P < .05),
Conclusion: Meloxicam, 15 mg/day caused a major reduction of maximum thromb
oxane production but no reduction in collagen- or arachidonic acid-induced
platelet aggregation and only minor increase of the closure time.