Objective: The purpose of this study was to use three analytic methods to measure serum calcium concentration to assess the magnitude and time course of the effects of four gadolinium-based contrast agents.
Subjects and methods: After providing informed consent, 12 healthy adult volunteers (mean age, 38.6 +/- 13.6 [SD] years) received i.v. injections of gadoversetamide, gadodiamide, gadopentetate dimeglumine, and gadoteridol at a dose of 0.1 mmol/kg. Blood samples were obtained before contrast administration and 5, 10, 15, 30, 60, 90, 120, 180, and 240 minutes after contrast injection. Serum calcium levels were measured with an orthocresolphthalein complexone method, an arsenazo III method, and inductively coupled plasma mass spectrometry (ICP-MS). Analyses of variance coupled with a Dunnett test were used to compare baseline serum calcium measurements with values at the different time points after injection.
Results: Administration of gadoversetamide or gadodiamide caused no significant change in serum calcium concentration measured with the arsenazo III and ICP-MS analytic methods. However, the orthocresolphthalein assay showed a transient decrease in serum calcium concentration after injection of gadoversetamide or gadodiamide. Injection of gadopentetate or gadoteridol produced no significant change in serum calcium values measured with the orthocresolphthalein, arsenazo III, and ICP-MS methods.
Conclusion: Administration of gadoversetamide or gadodiamide caused no significant effect on serum calcium concentration. Neither gadoversetamide nor gadodiamide interfered with measurement of serum calcium with the arsenazo III or ICP-MS method. However, the orthocresolphthalein method of measuring serum calcium produced a transient hypocalcemia artifact in the presence of gadoversetamide or gadodiamide.