Figure 5.

Metabolites of (A) Acetaminophen and (B) Ibuprofen and their proportions measured from urine of GCKD participants. Left column: Illustration of initial steps of metabolism.⁴³ Metabolites highlighted in bold have been reported by Loo et al.⁴² as main drug metabolites in urine, and were used to assess analgesic use based on metabolomics. Right column: Bar plot representing proportions of reported medication use (white) and of urine measurements of unmodified drug metabolites (4-acetamidophenol) and main metabolites (black and gray, respectively). The bottom bar of each bar plot panel represents a summary measure of the measured metabolites, and is used to evaluate the use of the respective medication based on metabolomics. Acetaminophen comb, combination of unmodified drug (4-acetamidophenol) together with at least two of the three main drug metabolites (light gray), or with all three main metabolites (dark gray); Ibuprofen comb, combination of at least two of the three main drug metabolites (light gray), or combination of all three main metabolites (dark gray); MCU, mercapturate (synonym, 3-[N-acetyl-L-cystein-S-yl] acetaminophen); NAPQI, N-acetyl-p-benzoquinone.