Saccharide-based contrast agents. Characteristics and diagnostic potential.

Since about 1980 tiny bubbles of gas ("microbubbles") have been known to be highly effective in ultrasonography because of enhancing backscatter ultrasound. After about 25 years of experimental work, the first industrial US contrast agent was approved by health authorities, the galactose microparticle SH U 454-Echovist, Schering AG, launched on the German market in 1991. Its major limitation is represented by the fact that it does not pass the pulmonary barrier and is confined to right heart abnormalities. Therefore another agent has been developed, the transpulmonary derivative of Echovist the galactose-based agent with the code number SH U 508 A (Levovist) which is in the late phase of clinical development for cardiac B-mode and Doppler blood pool US enhancement. A wide number of application areas can be foreseen for this contrast agent, which has been used for a multicenter trial. More than 1,200 patients were included in a European phase-III multicenter trial aimed at assessing the diagnostic efficacy and safety of SH U 508 A (Levovist). The patients included in the study had diagnostically insufficient Doppler signal intensity at routine Doppler or color Doppler vascular imaging. In more than 95% of the patients Doppler signal enhancement was achieved with at least one dose at the scheduled regimen, even in peripheral vessels. Enhanced Doppler US allowed a diagnosis to be made in many patients who would have otherwise undergone more invasive procedures. The diagnostic confidence, evaluated on a numerical rating scale (0-100) increased from 25.2 +/- 22.8% (prevalue) to 77.7 +/- 22.2% after Levovist (mean value +/- standard deviation, as calculated for a subgroup of 513 patients). Repeated i.v. injections were well tolerated. No specific risk was found for patients in any disease group.