Table 3.

Examples of ADME biomarkers that can be used to detect drug–drug interactions.

Enzymes or transporters	Potential endogenous biomarkers
CYP3A4/5	•4β-Hydroxycholesterol •Urinary 6β-hydroxycortisol to cortisol ratio •Urinary 1β-hydroxy-deoxycholic acid/total deoxycholic acid ratio
OATP1B1/1B3	•Coproporphyrin I (CPI) and CPIII •Glycochenodeoxycholate-3-sulfate (GCDCA-S) •Glycochenodeoxycholate 3-O-glucuro-nide (GCDCA-3G) •Glycodeoxycholate 3-O-glucu-ronide (GDCA-3G) •Hexadecanedioate (HDA) and tetrade-canedioate (TDA) •Unconjugated and conjugated bilirubin (UCB and CB)
OAT1/OAT3	•Kynurenic acid •Taurine (renal clearance) •6β-Hydroxyl cortisol (6βHC) •Glycochenodeoxycholate-3-O-sulfate (GCDCA-S) •Homovanillic acid (HVA) •Pyridoxic acid (PDA)
OCT2/MATE1/2κ	•Creatinine •N1-Methylnicotinamide (NMN)