Pediatric medication dosing is a complex process with many unique considerations not seen in other healthcare populations. Vendor-supplied dosing rule databases are commercially available for integration within many electronic health records order systems. The accuracy of these rules has not been evaluated in the informatics literature. Inaccurate or absent dosing rules in electronic order entry systems can lead to high numbers of false alerts and potentially compromise patient safety in an already vulnerable population. This study demonstrates that the accuracy of a vendor-supplied dosing rules database is suboptimal when compared with traditional dosing sources exposing a gap between formal dosing rules in commercial products and actual prescribing practices by pediatric care providers. More research on vendor-supplied databases is required to understand the effects of these products on safe prescribing in children.