Five Chinese pharmaceutical companies have been fined a combined total of 4 million yuan ($608,000) for acting in collusion to fix the price of a common medication.

The drug, allopurinol, is listed as an essential medicine in China and is widely used to treat gout and hyperuricemia, or abnormally high levels of uric acid in the blood.

The National Development and Reform Commission, the nation's top pricing regulator, found that Chongqing Qingyang, Jiangsu Shimaotianjie and Shanghai Xinyi, which have been the only three domestic producers of allopurinol tablets since 2014, reached monopoly agreements with two distributors, Chongqing Datong and Shangqiu Huajie over the drug.