Intravenous Contrast Agent Safety

The most commonly reported reactions associated with the injection of Gd-DTPA are: headache (6.5%), injection site coldness (3.6%), injection site pain or burning (2.5%), and nausea (1.9%). Recent adverse rates for Gd-DTPA are lower than this and comparable to those of Gadodiamide and Gadoteridol (1.4%-3% for headache, nausea, and dizziness; <1% for the others). The safety factor or ratio (ratio of the LD50 to the imaging dose) may be used to assess the relative acute toxicity of contrast agents. The elimination half-life for the Gd containg contrast agents range from 1.25-1.6 hours.
Gadolinium containing contrast agents usually has no effect on blood chemistries and hematologic studies except transient elevation of serum iron and bilirubin levels. These elevations peaked at 4 to 6 hours post injection and returned to baseline values in 24 to 48 hours. The mechanism of these elevations is uncertain but may be related to mild hemolysis. A 10%-11% increase in the activated partial thromboplastin time and thrombin time occurs in vitro with inhibition of platelet aggregation. The platelet aggregation inhibition is less than that seen with iodinated ionic contrast material and no bleeding problems are reported clinically.
Deoxygenated sickle erythrocytes align perpendicular to a magnetic field in in vitro studies raising the possibility of occlusive complications in patients with sickle cell anemia. No clinical reports of this potential problem are available.
Transient and mild drop blood pressure is reported in both animals and humans. A study of 1,068 patients reports hypotension in 0.3% of the subjects and other symptoms such as syncope probably associated with hypotension in 0.8%.33 Most of these symptoms occur 25-85 minutes after the injection.
Reports of several episodes of severe anaphylactoid reactions after IV injection of Gd- DTPA are published. The frequency of these reactions is about 1 in 100,000 doses. Potential risk factors may include a history of asthma and significant reaction to previously administered iodinated contrast material. It is suggested that the threshold for injecting Gd be raised, in those patients, based on an individual risk/benefit ratio. Prophylactic pharmacotherapy with antihistamines and corticosteriods, such as Greenbergers protocol, is suggested for high risk patients prior to contrast injections.