BEIJING (AP) — US drug maker Pfizer has lost a round in its legal battles with Chinese rivals over rights to names for its popular anti-impotence drug Viagra, a court employee reported yesterday.Pfizer and local drug makers are struggling over the Chinese patent and names for its “little blue pill,” a potentially lucrative product in a society with a long history of interest in drugs to improve sexual performance.

In the latest case, a Beijing court rejected Pfizer’s request to block a Chinese drug company from using the name “Wei Ge” for one of its products, said the employee of the Beijing Intermediate People’s Court. She refused to give her name.

Pfizer said “Wei Ge,” or “Mighty Brother,” was a name used by many Chinese to describe Viagra, making it improper for another company to use the name.

But the Beijing court’s ruling, issued in late December, said the Chinese company had properly registered the name, said the court employee. Phone calls to Pfizer’s China headquarters in Beijing were not answered.

Pfizer sells Viagra in China as “Wan Ai Ke” but has challenged Chinese companies accused of using variations on the name or copying the look of its distinctive blue pill.

In a separate ruling in December, the same Beijing court upheld Pfizer’s Chinese patent for Viagra and ordered two Chinese rivals to stop making generic versions under the name “Wei Ge.”

At least a dozen Chinese drug companies want the right to make sildenafil citrate, the main active ingredient in Viagra.