The chief executive of Sanofi admitted that the French pharmaceutical giant had underperformed in emerging markets last year, after reporting a decline in quarterly sales on Thursday.
"We did not perform as well as we should have. We had an issue with our Brazilian generics business. We had some distribution issues in China," CEO Christopher Viehbacher told CNBC.
Sanofi reported that sales of generic (non-patented) drugs fell 8.2 percent in 2013 to 1.6 billion euros ($2.2 billion). In a news release it said this reflected "challenges in Brazil and lower sales of authorized generics in the U.S."
However, in the last three months of the year generic sales picked up, with Brazilian revenue growing by 23.6 percent or 59 million euros.
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Overall, Sanofi's fourth-quarter turnover was hit by the rise in the euro against currencies such as the Brazilian real, the Venezuelan bolivar and the Russian ruble. Net sales fell by 0.8 percent to 8.5 billion euros, topping the 8.4 billion euros forecast by analysts in a Reuters poll.
"We always report our results at constant exchange rates. Some years we win, some years we don't," said Viehbacher.
Sanofi shares closed around 2.8 percent lower after it reported earnings, underperforming the benchmark Cac40 which closed provisionally 1.7 percent higher.
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Markets appeared disappointed by Sanofi's 2014 earnings per share (EPS) growth outlook of 4-7 percent, which Viehbacher defended.
"Four to seven percent is actually a very good growth rate. There are not many pharmaceutical companies who are going to grow over the next two to three years," he said.
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Deutsche bank analyst Mark Clark said: "Sanofi has entered 2014 with stronger momentum than expected and, although EPS guidance is disappointing if taken at face value, it is likely to prove overly conservative."
Viehbacher previously worked for 20 years at Sanofi's U.K. rival GlaxoSmithKline, which posted quarterly sales on Wednesday that narrowly beat expectations. Its fortunes appear to be looking up after last year's bribery scandal, which saw GSK executives detained by the Chinese government.
—By CNBC's Katy Barnato. Follow her on Twitter: @KatyBarnato