Indigo Carmine Visualization Duration in Urine: A Randomized Kinetics Study

Importance Despite its frequent use for visualization of ureteral efflux during pelvic/abdominal surgery, there are limited data on indigo carmine pharmacokinetics and duration of blue color in postdose urine. Understanding how long the blue color persists allows the clinician to make accurate assessments of the urinary system during complex surgical procedures. Objectives This study observed the plasma and urinary pharmacokinetics of indigo carmine in healthy volunteers and the voided urine color. Study Design This study was an open-label, randomized clinical trial in 16 healthy participants who received either a 2.5-mL or a 5.0-mL intravenous injection of indigo carmine. Blood (pre, 2, 5, 7, 10, 15, 20, 30, 40 minutes and 1, 2, 3, 4, 6, 12 hours post) and urine (predose, 0–2, 2–6, 6–12 hours post) were collected. The first postdose stool was collected. Results Plasma concentration peaked within 5 minutes, and all plasma concentrations were below the limit of quantification by 2 hours postdose. The estimated plasma half-life of indigo carmine was 12 minutes. Voided urine through 2 hours postdose was visibly discolored compared with the matched predose urine. In some cases, urine discoloration persisted through 6 hours (10/16) and 12 hours (1/16). Unchanged indigo carmine eliminated in stool was observed in 4 of 16 participants (25%). Conclusions The short half-life and rapid urinary excretion of indigo carmine favor its clinical use for intraoperative cystoscopy and are consistent with the reported median time of 6 minutes postinjection to ureteral efflux in patients undergoing surgical procedures.