Background: Lumbar interlaminar epidural steroid injections (ESIs) are one of the most commonly performed procedures in pain medicine, but little is known about the serum levels of steroids following injection into the epidural space. The primary objective of this study was to investigate the pharmacokinetics of fluoroscopy-guided epidural-administered triamcinolone acetonide in a cohort of patients with chronic low-back pain seeking treatment in a pain medicine clinic.
Methods: The study cohort included 10 patients undergoing a fluoroscopically guided L4-L5 or L5-S1 lumbar interlaminar ESI at a pain medicine specialty clinic. Blood was collected prior to the ESI and on days 1, 2, 4, 6, 8, 14, 21, 28, 35, and 42 following the injection. The sample extract was analyzed by tandem mass spectrometry.
Results: The terminal elimination half-life of epidural-administered triamcinolone in a noncompartmental analysis was 523 hours. In the noncompartmental analysis, peak triamcinolone concentrations of 4.1 ng/mL were detected within 24 hours after administration.
Conclusions: The pharmacokinetics of epidural-administered triamcinolone is consistent with previously observed adverse effects of the drug on endocrine function. The pharmacokinetics of other epidural-administered steroids should be determined and incorporated in clinical trials to investigate the potential associations between serum levels, clinical outcomes, and potential adverse endocrine effects.