US drug giant Pfizer filed an appeal with a Chinese court against a July decision revoking its national patent on the anti-impotence drug Viagra. The challenge to the decision by China's State Intellectual Property Office was filed Tuesday with the Beijing First Intermediate People's Court with analysts carefully watching what could become a test case for China's commitment to intellectual property rights. Under Chinese law the court has seven days to decide whether to place the case for trial, although a decision is not expected until after the October national holiday week. The news coincided with an announcement from Pfizer that it had been granted official approval to expand the sale of Viagra to pharmacies from hospitals. The drug generated US$1.88 billion in worldwide sales for Pfizer last year. However, sales in China were limited because only hospitals could sell the drug.