Influence of age on the enantiomeric disposition of ibuprofen in healthy volunteers.
OBJECTIVE
To determine the influence of age on the enantioselective disposition of ibuprofen in humans.


METHODS
Healthy young (n = 16; aged 20-36 years) and elderly (n = 16; aged 66-84 years) volunteers were given a 400-mg oral dose of racemic ibuprofen, and blood and urine samples were collected for 24 h post drug administration. Serum concentrations, total and free, and urinary excretion of both enantiomers of ibuprofen together with the urinary excretion of the stereoisomers of the two major metabolites of the drug, both free and conjugated, were determined by high-performance liquid chromatography.


RESULTS
Ageing had little effect on the distribution and metabolism of R-ibuprofen, unbound clearance of the R-enantiomer via inversion being approximately two-fold that via noninversion mechanisms in both age groups. In contrast, the free fraction of S-ibuprofen was significantly greater [33%; young 0.48 +/- 0.10%; elderly 0.64 +/- 0.20%] mean difference -0.16; 95% confidence interval (CI) -0.05, -0.27; P < 0.01; and the unbound clearance of the drug enantiomer was significantly lower (28%; young 15.9 +/- 2.2 l min-1; elderly 11.5 +/- 4.1 l min-1; mean difference 4.4; 95% CI 2.12, 6.68; P < 0.001) in the elderly. The metabolite formation clearances of S-ibuprofen via glucuronidation, and oxidation at the 2- and 3- positions of the isobutyl side chain decreased by 24, 28 and 30%, respectively, in the elderly compared with the young, the differences between the two age groups being significant in each case (P < 0.05).


CONCLUSIONS
Following administration of racemic ibuprofen age-associated stereoselective alterations in drug disposition have been observed, with the elderly having increased free concentrations and lower unbound clearance of the S-enantiomer in comparison with the young. In contrast, the handling of the R-enantiomer is essentially unaltered with age. The results of this study indicate that the elderly have an increased exposure to the active ibuprofen enantiomer and thus some caution may be required when using this drug in this age group.
Tan
Soo Choon
SC
Department of Pharmacy, King's College, London, UK.
Patel
Bhavesh K
BK
Jackson
Stephen H D
SH
Swift
Cameron G
CG
Hutt
Andrew J
AJ
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000378:metabolism*; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000737:chemistry / Q000378:metabolism* / Q000493:pharmacokinetics; D006801:Humans; D007052:Ibuprofen / Q000737:chemistry / Q000378:metabolism* / Q000493:pharmacokinetics; D013237:Stereoisomerism
D000894:Anti-Inflammatory Agents, Non-Steroidal; D007052:Ibuprofen