GlaxoSmithKline has appointed Emma Walmsley, head of consumer healthcare, as its new chief executive, after considering internal and external candidates.
Walmsley, who joined the drugmaker in 2010 from L’Oreal, will replace Andrew Witty who had previously announced his decision to retire next March.
The decision will disappoint investors such as Neil Woodford, a top shareholder and a critic of the drugmaker's current structure, who had wanted to see an outsider replace Witty.
However, Walmsley had always been tipped as a strong internal candidate, along with pharmaceuticals boss Abbas Hussain and manufacturing head Roger Connor.
Her appointment is likely to be seen as a signal that GSK will retain the consumer business as a core part of its operations.
"Under Andrew’s leadership, GSK has successfully developed into a company with market-leading positions in pharmaceuticals, vaccines and consumer healthcare," Chairman Philip Hampton said.
"These provide excellent platforms for sustainable, long-term growth, and we are confident Emma will successfully build on these strengths."
At the helm since 2008, Witty has struggled with flagging sales and profits, although the picture is now improving.
Some investors and analysts have questioned his focus on a consumer health business that ranges from headache pills to toothpaste.
Other drugmakers have enjoyed better share price performance in recent years by riding a wave of innovation in disease areas such as cancer.
The company has about 1,500 employees in Ireland, in various facilities around the country including Dublin, Sligo, Dungarvan and Cork.