Calcium Carbonate for Elemental Lead Ingestions: Effect of Alkalinization on Elemental Lead Solubility in a Simulated Gastric Environment.

Abstract

Acute ingestion of elemental lead foreign bodies has resulted in multiple pediatric deaths. Elemental lead is relatively insoluble at alkaline pH. Furthermore, calcium decreases lead absorption by interfering with the lead absorptive receptor. We hypothesize that alkalinization of gastric fluid with an oral calcium-containing agent, such as calcium carbonate, will decrease lead solubility, thus reducing the potential for systemic lead absorption and toxicity. This was an in vitro controlled study. One lead sphere (00 buckshot, cast 30 days prior) was randomly placed in each of ten tubes containing 20 mL simulated gastric fluid, with five tubes having 500 mg calcium carbonate added at 20 min and 140 min. We measured the fluid pH and the lead concentrations hourly for 4 h. We compared the median amount of total lead liberated after 4 h between the two groups using the Mann-Whitney U test. The pH of the gastric fluid only tubes remained 1 at every measurement, and the pH of the gastric fluid + calcium carbonate tubes was 6 at every measurement. At hour 4, the total amount of lead liberated in the soluble fraction in the control group vs the calcium carbonate group was 850 vs 12.4 mcg (95% CI for absolute difference: 605-964 mcg; p = 0.0079). Calcium carbonate antacid alkalinizes gastric fluid pH and dramatically decreases the total amount of solubilized lead by 60-fold. This project lends foundational evidence to a low-cost, widely available, pre-hospital strategy to decrease lead absorption after acute elemental lead ingestions.