Gadolinium zeolite as an oral contrast agent for magnetic resonance imaging

The purpose of this study was to evaluate efficacy and safety of a gadolinium (Gd) zeolite suspension as an oral MRI contrast agent. Serial dilutions of GADO-LITE Oral Suspension 1,2-300 micrograms of Gd(III)/mL) were prepared. MRI (T1 and T2 weighted) of standards and dogs (precontrast and postcontrast) were performed. Toxicity and Gd absorption were also assessed. Subsequently, 30 normal male adult volunteers were divided into six groups of five subjects each. Gd zeolite po suspension was administered before and after MRI in volumes and concentrations ranging from 250 to 1500 mL; 6 to 60 micrograms of Gd+3/mL. The images were rated (efficacy score) by a blinded reader. Vital signs, blood chemistries and urinalysis were recorded. Gadolite Oral Suspension produced excellent enhancement of the dog gastrointestinal (GI) tract. No toxicity or absorption of Gd was observed in dogs receiving doses up to 4 times the anticipated human dose daily for 14 consecutive days. In clinical trials, Gd zeolite significantly improved the efficacy scores for all groups and all pulsing sequences (all P values < .05). Efficacy scores and signal intensities generally increased with concentration and volume. No Gd was detected in blood or urine specimens. No significant adverse events were reported. Gd zeolite is a promising contrast medium for enhancement of the GI tract in MRI.