THE PHARMACOKINETICS OF PIROXICAM IN ELDERLY PERSONS WITH AND WITHOUTRENAL IMPAIRMENT

1 Piroxicam pharmacokinetics were assessed in three groups of subjects : (1) young healthy volunteers, (2) healthy elderly subjects (mean +/- s.d. creatinine clearance 88 +/- 13 ml min-1), and (3) elderly patien ts with renal insufficiency (creatinine clearance 60 +/- 10 ml min-1) following the administration of piroxicam 20 mg as a single dose and a fter chronic dosing of 20 mg once daily for 4 weeks. 2 Piroxicam and 5 '-hydroxypiroxicam concentrations were measured by h.p.l.c. in serum a nd urine samples collected for 96 h after the single dose and for 144 h after chronic dosing. Unbound concentrations of piroxicam were deter mined by ultrafiltration. 3 Elimination half-lives, steady state conce ntrations of piroxicam and 5'-hydroxypiroxicam, clearances of total an d unbound piroxicam, volumes of distribution normalized for body weigh t, and urinary recovery of 5'-hydroxypiroxicam were not influenced by age or renal function. Volumes of distribution after the single dose w ere significantly lower in women compared with men (mean +/- s.d. 10.0 +/- 2.9 l vs 12.9 +/- 5.0 l; 95% confidence interval of the differenc e 0.1 to 5.6). 4 Percent unbound piroxicam values were 1.46 +/- 0.3% a fter the single dose and 1.45 +/- 0.2% at steady state. There were sig nificant reductions in clearance and clearance of unbound piroxicam be tween single and chronic doses. The half-lives of 5'-hydroxypiroxicam (80.9 +/- 44 h) were significantly longer than those of piroxicam (54. 9 +/- 26 h) after chronic dosing.