While Ishaq Siddiqi, market strategist at ETX Capital, added: "The scandal certainly drove (the fall in sales) but it seems GSK is now looking to put that episode behind them... but investors will continue to express their hesitancy until litigation cases are brought forward and GSK officially moves past the incident and restores reputational damage."
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Glaxo has since announced that by 2016 it will cease paying healthcare professionals to speak at, or attend, medical conferences —an industry-wide practice. It is also removing individual sales targets for its employees.
More generally, 2013 was a good one for the industry, with the number of new drug and treatment approvals starting to rise after years of decline.
Glaxo itself has several potential "blockbuster" drugs, which are due to be launched in the near-term. There are also several late-stage drugs reaching maturity this year.
"As we look back at 2013, the most notable thing is the R&D approvals we've had, which position us very well for the future and give us the confidence behind the guidance that we've given for 2014," Dingemans added.
Shares of Glaxo traded 2.2 percent higher on the London Stock Exchange after it reported results.
Meanwhile, U.S. drugmaker Merck reported sales that were narrowly below expectations on Wednesday. Its sales were hit by competition from cheaper generic medicines.