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

TCA frozen for up to 1.8 years retains biological activity comparable to fresh product for ACTH stimulation testing.

This prospective case-crossover study investigated whether tetracosactide acetate (TCA), a synthetic ACTH analogue used in adrenal function testing, retains its biological activity after long-term storage in plastic syringes at -20°C. Eight healthy adult Beagles (4 males, 4 females) were divided into two groups and received 5 μg/kg IV of either frozen or fresh TCA on two occasions, four weeks apart, in a crossover design. Frozen TCA had been stored for a median of 1.8 years (IQR 1.5–1.9 years). Adrenal steroid responses were assessed using liquid chromatography-tandem mass spectrometry, measuring cortisol and other steroid metabolites including 17-hydroxyprogesterone (17-OHP). Statistical analysis employed a general linear mixed model accounting for treatment, period, sequence, timing, and individual dog variation. Results demonstrated that frozen TCA produced steroid responses comparable to fresh TCA. Post-stimulation cortisol concentrations were 248 nmol/L (frozen) versus 254 nmol/L (fresh), with a statistically significant but clinically negligible difference (P = .037). The 17-OHP responses were not significantly different between groups (P = .09). The authors conclude that long-term frozen TCA in plastic syringes is a viable, cost-effective alternative to fresh product, particularly relevant during drug supply shortages. Limitations include the small sample size (n=8), restriction to healthy dogs only, and the use of IV rather than IM administration, which may limit direct extrapolation to standard clinical practice.

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