Gentisic acid: a new stabilizer for low tin skeletal imaging agents: concise communication.

In vitro stabilization of low-tin bone-imaging agents has previously been achieved with ascorbic acid. In this study gentisic acid is shown to be an equally effective antioxidant for the (1-hydroxyethylidene) diphosphonate (HEDP) and hydroxymethylenediphosphonate (HMDP) skeletal agents. In vitro studies show less than 2% free sodium [99mTc] pertechnetate at 24 hr with the gentisic acid stabilizer. Studies in guinea pigs at 3 and 24 hr--whether with C-14 or H-3-labeled gentisic acid as stabilizer--show no alteration in the biodistribution of either skeletal imaging agent by the addition of the gentisic acid. Gentisic acid is a safe and effective stabilizer, and clinical studies have shown bioequivalency with ascorbic acid.