Pfizer has taken a Chinese pharmaceutical company to court over an alleged infringement of its copyright for the erectile dysfunction drug Viagra, according to a report on the Beijing News service.

The action against Guangzhou Welman Pharmaceutical was heard in a Beijing court yesterday but has yet to reach a verdict.

Earlier this year, a Chinese court overturned a previous decision made in 2004 that rendered Pfizer's intellectual property for a certain ingredient in Viagra (sildenafil citrate) invalid, effectively opening up the market to copycat versions of the drug. A group of 12 Chinese drugmakers immediately said they would appeal the ruling.

The decision to uphold Viagra's patent falls in line with China's stated intention of improving the intellectual property environment in a country renowned for counterfeit goods.