From about 50 percent this year, the US share of the worldwide pharma market will fall to about one-third in 2008, according to a new report by IMS Health. Meanwhile, sales in emerging economies in China, Brazil, Turkey, Mexico and elsewhere are booming, but the gains will be offset by the loss of patent protection for profitable drugs worth $20 billion in annual sales next year, the market research firm predicts.

Expected global sales growth of 5 percent to 6 percent, worth between $735 billion to $745 billion, in 2008 compares with 6 percent to 7 percent growth in 2006 that netted between $695 billion to $705 billion, the Associated Press writes. In the US, prescription drug sales growth of 4 percent to 5 percent, or $295 billion to $305 billion, is forecast.

As US patents expire for Johnson & Johnson’s Risperdal schizophrenia treatment and Merck’s Fosamax osteoporosis med, global sales growth of generic drugs will rise 15 percent to $70 billion. IMS expects 29 new drugs to launch next year, but most of them will target less common diseases, not offsetting lost sales of drugs like Merck’s Zocor, which lost patent protection this year, the AP writes.

Generic manufacturers like Mylan and Barr Pharmaceuticals will continue to make inroads in emerging markets. IMS estimates prescription drug sales in China, Brazil, Mexico, Turkey and other emerging economies will account for 25 percent of the global market in 2008, although economic growth in the developing world won’t benefit brand-name manufacturers as much until those countries can afford more expensive, innovative medicines.

The IMS report of slowing sales growth comes as the FDA has grown more cautious about new drug approvals. In 2007, the FDA has slapped new warnings on drugs from Glaxo, Amgen and Lilly, and rejected highly anticipated products from Sanofi-Aventis and others. While drug makers say recently passed laws giving FDA additional powers to regulate drugs may ease the agency’s defensive stance, IMS foresees more warning labels and slower approvals.