China's Got the Litigation Bug: China is likely to see an increase in patent lawsuits after domestic drugmakers won victories against overseas competitors in cases against the Pfizer drug Viagra and the GlaxoSmithKline drug Avandia, legal experts have said. "I would not be surprised to see many more challenges such as these," said Janice Mueller, a professor at the University of Pittsburgh's School of Law.

Glaxo, Europe's largest drugmaker, last week gave up a fight to protect a key ingredient in Avandia, its top diabetes treatment, a month after China revoked the local patent for Viagra, the world's best-selling impotence drug.

Chinese drugmakers are becoming more willing to use legal means to secure competitive advantages, three years after the nation joined the World Trade Organization. The trend may hurt sales for foreign companies in China's $10 billion drug market and lead to more trade disputes.

"It isn't hard to find loopholes" in Chinese patents held by overseas drugmakers, said Xu Guowen, a Beijing-based lawyer who led the cases against Viagra and Avandia. "All I need is to find one weakness and I can break your patent."

-- Loopholes? Is that what he considers prior art?