Updates share price in first paragraph and adds detail from third paragraph

By Scott Murdoch

SYDNEY, Feb 13 (Reuters) - Shares of Australia's Sigma Healthcare SIG.AX gained more than 3% in early trading on Thursday in the firm's first session since it finalised a merger with Chemist Warehouse to create a A$31 billion ($19.47 billion) pharmacy and retail giant.

The value of the merger was A$8.8 billion when the deal was announced in December 2023, but Sigma shares have increased more than three-fold.

The stock was up 0.2% on Thursday when trading began, but gained steadily to last trade 3.4% higher at A$2.86.

Almost 100% of Sigma shareholders approved the deal that involved Sigma paying A$700 million plus stock to Chemist Warehouse's founders for the business. It took more than a year to gain regulatory approval.

Former Chemist Warehouse shareholders now own 85.8% of the merged company that will supply 1,200 Sigma-aligned pharmacies and own more than 658 Chemist Warehouse outlets, according to regulatory filings.

Chemist Warehouse's founders control 14.25% of the merged company, the deal's documents showed.

($1 = 1.5918 Australian dollars)

(Reporting by Scott Murdoch; Editing by Chris Reese and Jamie Freed)

((Scott.Murdoch@thomsonreuters.com;))