Steroidal response following intravenous administration of long-term frozen tetracosactide acetate in healthy Beagles.

[en] BACKGROUND: The adrenocorticotropic hormone (ACTH) stimulation test is used to assess adrenal function. The effects of extended freezing of tetracosactide acetate (TCA), an ACTH analogue, on test performance, remain unexplored.
HYPOTHESIS/OBJECTIVES: To determine whether TCA retains its biological activity to induce adrenal steroid production when stored in plastic syringes and frozen at -20 °C for prolonged period.
ANIMALS: Eight adult experimental Beagles divided into 2 groups of 2 males and 2 females each.
METHODS: Prospective case-crossover study. Each dog received 5 μg/kg IV of TCA on 2 occasions, 4 weeks apart (period P1-washout-period P2). Group 1 received frozen then fresh TCA; group 2 received fresh then frozen TCA. Pre- and post-administration blood samples were analyzed at both study periods for cortisol and other steroid metabolites using liquid chromatography-tandem mass spectrometry. A general linear mixed model was used with TCA (fresh vs frozen), period, sequence and timing as fixed factors, and dog as random factor.
RESULTS: Frozen TCA stored for a median time of 1.8 years (IQ range 1.5-1.9) induced similar steroid metabolite responses compared with fresh TCA. Median T1 cortisol concentrations were 248 nmol/L (IQ range 231-272) with frozen TCA and 254 nmol/L (IQ range 249-262) with fresh TCA (P = .037). Median T1 17-OHP concentrations were 0.73 μg/L (IQ range 0.67-0.85) with frozen TCA 0.79 μg/L (IQ range 0.71-1.17) with fresh TCA (P = .09).
CONCLUSIONS AND CLINICAL IMPORTANCE: Long-term freezing of TCA in plastic syringes offers a cost-effective strategy and practical alternative during supply shortages.