For the first time ever, global spending on prescription drugs has topped $600 billion, even as growth slowed in Europe and North America.

Worldwide sales of prescription medicines rose 7% to $602 billion, according to IMS health, the pharmaceutical information and consulting company. The United States still accounts for the lion's share of that with $252 billion in annual sales, but sales in it and the other nine biggest markets grew by only 5.7%. But emerging markets such as China, Russia, South Korea and Mexico outpaced those markets, growing a whopping 81%.

Pfizer's cholesterol pill Lipitor remains the best-selling drug in the world for the fifth year in a row. Its annual sales were $12.9 billion, more than twice as much as its closest competitors like Plavix, the blood thinner from Bristol-Myers Squibb and Sanofi-Aventis; Nexium, the heartburn pill from AstraZeneca; and Advair, the asthma inhaler from GlaxoSmithKline.

One thing that's visibly lacking from the list of international bestsellers is a biotech drug. In the US, three anemia treatments, two from Amgen and one from Johnson & Johnson, have cracked the top ten. But the biotech revolution brought by drugs made of protein that must be injected hasn't had quite the same impact worldwide, although the category still grew 17% to $53 billion, states the report.

The difficulty for big pharma is that there are lots of $1 billion drugs but few mega-blockbusters. The second-biggest drug generates half as much revenue as Lipitor, and the tenth top-selling drug. Wyeth's anti-depressant Effexor, generates a "mere" $3.8 billion. That means even if new medicines are successful, they may not fill the holes created as drugs go generic.

That's one reason why Bristol and Sanofi were under pressure to reach a settlement in their Plavix patent dispute with generic drug maker Apotex, announced last week. However, Aitken highlights the potential of several new medicines launched in the past year, including diabetes treatment Byetta, co-marketed by Eli Lilly and Amylin Pharmaceuticals, and Lunesta, an insomnia drug made by Sepracor.

The two key drug launches this year are of Sutent, Pfizer's first big entry into cancer drugs, and Acomplia, the anti-obesity pill being developed by Sanofi-Aventis. Sutent is already on the market, although sales data are not yet available. Acomplia has been delayed at the US Food and Drug Administration and rejected as a stop-smoking drug. Some cardiologists, who are excited about the drug because of its potential to reduce the risk of heart disease, are also worried about side effects.

Acomplia works by blocking the same brain receptor that makes pot smokers hungry; psychiatric symptoms like anxiety are one of the most common reasons patients stopped taking Acomplia in clinical trials, added the report.