UPDATE 2-Walmart tie-up helps McKesson beat profit estimates

(Adds background on Walmart partnership, Amazon's rumored entry into drug supply chain)

Feb 1 (Reuters) - McKesson Corp, the biggest U.S. drug distributor, posted a bigger-than-expected quarterly profit, as its tie-up with Walmart continued to help the company buy generic drugs at lower prices.

Drug distributors have been tying up with retailers like Walmart and retail pharmacies such as Walgreens Boots Alliance Inc for huge discounts on generic drug purchase.

McKesson, which partnered with Walmart in 2016, on Thursday also raised its 2018 adjusted earnings forecast range to $12.50-$12.80 per share, from $11.80-$12.50 as a result of a lower tax rate and share count.

The company's profit jumped nearly 43 percent to $903 million, or $4.33 per share, in the third quarter ended Dec. 31, as it booked a benefit of about $370 million related to changes to U.S. tax laws.

Excluding items, the company earned $3.41 per share, above the average analyst estimate of $2.94, according to Thomson Reuters I/B/E/S.

Total revenue increased about 7 percent to $53.62 billion.

The results come at a time of rumors about Amazon.com Inc's entry into the drug supply chain. On Tuesday, Amazon, Berkshire Hathaway Inc, and JPMorgan Chase & Co said they will form a company to cut health costs for hundreds of thousands of their employees. (Reporting by Anuron Kumar Mitra and Manas Mishra; Editing by Maju Samuel)