Corticosteroid and Cortisol Serum Levels Following Intra‐articular Triamcinolone Acetonide Lumbar Facet Joint Injections

Abstract

Facet joint steroid injections are used to treat chronic low back pain. However, little is known about the systemic absorption and serum levels of steroids following intra-articular facet joint injections. The primary objective of this preliminary study was to investigate the pharmacokinetics of triamcinolone acetonide following fluoroscopically guided intra-articular lumbar facet joint injections in a cohort of patients with chronic low back pain. A secondary aim was to investigate the effects of triamcinolone on serum cortisol levels following lumbar facet joint injections. The study cohort included 5 patients undergoing fluoroscopically guided intra-articular lumbar facet joint injections at a pain medicine specialty clinic. Blood was collected prior to the injections and on days 1, 2, 4, 6, 8, 14, 21, 28, 35, and 42 following the injections. The terminal elimination half-life of triamcinolone in a noncompartmental analysis was 213 hours. The peak median triamcinolone concentration of 3.6 ng/mL was detected within 24 hours after the injections. Serum cortisol levels were < 30 ng/mL for an average of 4.4 days. The maximum effect of triamcinolone on cortisol suppression was observed with triamcinolone serum levels of > 1.9 ng/mL. The peak serum concentration of triamcinolone following intra-articular facet joint injections occurred within 24 hours. The median terminal elimination half-life was 213 hours, but baseline cortisol levels were suppressed for an average of 4.4 days. Clinically, the prolonged half-life and endocrine effects of triamcinolone could increase the risk for serious drug-drug interactions in patients taking medications that inhibit corticosteroid metabolism.