Piroxicam is one of the nonsteroidal anti-inflammatory drugs of the oxicam class commonly used in both veterinary and human medicine.  Anti-inflammatory and pharmacokinetics of piroxicam (20 mg/kg b. wt.) via intramuscular (i.m) injection were studied in normal and joint inflamed male rats. Injection of complete Freund's adjuvant in the right hind rat's paw resulted in biphasic edematous inflammatory thickness, immediate acute phase started at the 4th day followed by a chronic phase with marked edema at day 14 of injection. Treatment with piroxicam (20mg/kg b.wt.) for 28 day resulted in significant decrease in thickness of edema by 46.15, 57.40, 47.16, 53.57, 45.65 and 51.13% in days 4, 10,17,21,24 and 28 days, respectively.
Treatment of arthritic rat with 20 mg/kg b. wt i.m piroxicam for 28 days showed a significant decrease in the arthritic index (2.00 ± 0.09 and 0.80±0.01) from day 10 to day 28 as compared with arthritic index in non-treated (2.80 ± 0.18 and 6.20 ± 0.15 ), respectively.
Plasma samples were collected after 2,4,6,8,10,12,24 and 48 hours for analysis of plasma piroxicam concentration. The obtained data showed a non-significant increase in plasma piroxicam concentration in joint inflamed rats than that of normal rats. The calculated pharmacokinetic parameters revealed a short t0.5 absorption (t0.5ab) 2.10 ± 0.345 hrs and 1.75 ± 0.100 hrs, and prolonged elimination half-life time (t0,5el) 14.01 ± 0.730 and 20.61 ± 0.921 hrs in normal and joint inflamed rats, respectively.   Slow elimination rate (Cl/F) (0.12 ± 0.003 and 0.08 ± 0.003 (mg/kg)/ (μg/ml)/h), t0.5el as well as prolonged MRT (23.24 ± 0.666 and 32.26 ± 1.261 hrs) in normal and joint inflamed rats, respectively.
In conclusion: Piroxicam in dose of 20mg/kg/ b.wt via i.m has an anti-inflammatory effect in rat with joint inflammation and has non-significant higher and prolonged plasma concentration in inflamed joint rats than in normal.