Comparison of serum cortisol concentrations in clinically normal dogs after administration of freshly reconstituted versus reconstituted and stored frozen cosyntropin.

OBJECTIVE: To evaluate the biological stability of reconstituted cosyntropin after storage at -20 C for 2, 4, and 6 months. DESIGN: Prospective study. ANIMALS: 10 clinically normal dogs. PROCEDURE: Serum cortisol concentrations in dogs were determined before and 1 hour after administration of freshly reconstituted cosyntropin (synthetic ACTH) or cosyntropin that had been reconstituted and stored frozen at -20 C in plastic syringes for 2, 4, and 6 months. Cosyntropin was administered at 5 micrograms/kg (2.3 micrograms/lb) of body weight, i.v. RESULTS: Baseline serum cortisol concentrations were similar at each sampling time. Compared with the effects of freshly reconstituted cosyntropin, administration of cosyntropin that had been frozen did not have a significantly different effect on serum cortisol concentrations. CLINICAL IMPLICATIONS: Cosyntropin can be reconstituted and stored frozen at -20 C in plastic syringes for 6 months with no adverse effects on bioactivity of the polypeptide.