The 43-year-old head of Glaxo’s European pharma division was chosen by the board at the end of last week, beating out Chris Viehbacher, who heads the US unit, and David Stout, the chief operating officer. Witty will succeed JP Garnier, who turns 60 this month, in May.

Witty, who joined Glaxo in 1985 and became head of the European unit in 2003, has worked in the US, Asia and South Africa, and is credited with successfully reorganizing the European business. But he takes over at a precarious time. The drugmaker is struggling as older meds lose patent protection and is still reeling from the controversy over its Avandia diabetes pill, which earlier this year was linked to increased heart attack risks.

“Andrew’s appointment follows a rigorous selection process by the board of directors,” says Glaxo chairman Chris Gent, in a statement. “The fact that we have been able to select a successor to JP from three strong internal candidates is a testament to the quality of management at Glaxo.” Now, though, there’s speculation the process may prompt Viehbacher and Stout to consider leaving.

“He’s a pretty young guy,” Peter Cartwright, an analyst at Evolution Securities, tells Bloomberg News. “Time is on his side. He’s going to be in the job for a while, and he’ll have time to do a full review of the business.” His European knowledge “will be valuable for guiding the U.S. business as it faces not dissimilar challenges,” Kevin Wilson, an analyst at Citigroup in London, wrote in a note, the wire service reports.

Revenue fell in the first quarter as demand for Glaxo’s top-selling drugs slowed and the company lost patent protection on the Flonase allergy spray, the Zofran nausea drug and Wellbutrin XL antidepressant. Then came the New England Journal of Medicine study maintaining Avandia, which was the world’s best-selling diabetes pill, increased the risk of heart attacks by 43 percent. Prescriptions subsequently plunged - the Avandia franchise is down 60 percent this year, Alexandra Hauber, a Bear Stearns analyst, pointed out in an investor note this morning.

Witty, a graduate of Nottingham University, held positions as director of pharmacy and distribution and international product manager. Outside the U.K., he was director for south and east Africa as well as marketing manager for Glaxo’s U.S. unit before moving to Singapore as an executive in the Asia Pacific region.