Boehringer Ingelheim said it would purchase the US marketing rights to heartburn drug Zantac for $509.5 million as part of Pfizer’s sale of its consumer unit to Johnson & Johnson. In a statement about the purchase, Boehringer Ingelheim Corp. president and CEO J. Martin Carroll said Zantac, an OTC drug, complements the firm’s existing nonprescription franchise, which includes laxative Dulcolax. Zantac will be distributed through the same retail channels as the Dulcolax business, which will allow for increased promotion and marketing efficiencies, Carroll said. Pfizer is selling Zantac to help facilitate FTC approval of the planned, $16.6 billion sale of its Consumer Healthcare business to J&J, a deal expected to close by year’s end. Boehringer Ingelheim GmbH is the world’s biggest closely held drugmaker.