Measurement of serum calcium concentration after administration of gadoversetamide in dogs.

To measure serum calcium concentration with three different analytic methods after administration of gadoversetamide and three other gadolinium chelates in dogs. Six dogs were injected with 0.1-, 0.3-, 1.0-, and 3.0-mmol/kg doses of gadoversetamide; 1.0-mmol/kg doses of gadodiamide, gadopentetate, and gadoteridol; and a 6-mL/kg dose of saline. Baseline blood samples were collected before injection; 5, 15, 30, and 60 minutes after each treatment; and 2, 4, 6, 12, and 24 hours after each treatment. Serum calcium levels were measured with inductively coupled plasma mass spectrometry, an arzenazo III dye assay, and an orthocresolphalthalin (OCP) complexone system. Analysis of variance coupled with the Dunnett procedure was used to compare serum calcium concentrations at different time points after injection with baseline values. Administration of gadoversetamide caused no decrease in serum calcium levels, as measured with inductively coupled plasma mass spectrometry or arzenazo III analytic techniques. In contrast, OCP assays showed a significant (P <.05) decrease in serum calcium values after administration of gadoversetamide. The decrease in serum calcium values peaked immediately after injection, and serum calcium values quickly returned to baseline. Injection of gadodiamide caused a significant (P <.05) decrease in the value of serum calcium when analyzed with the OCP technique but not when analyzed with inductively coupled plasma mass spectrometry or arzenazo III assays. In contrast, administration of gadopentetate or gadoteridol produced no significant change in serum calcium values, regardless of analytic method. Gadoversetamide and gadodiamide caused a transient artifact in measurement of serum calcium levels with an OCP assay but not with an arzenazo III technique or inductively coupled plasma mass spectrometry. The presence of gadopentetate or gadoteridol in the blood did not affect measurement of serum calcium levels.