Shares in Alibaba Health Information Technology Ltd sank 20 percent on Thursday, after the digital-healthcare outfit was accused of holding a monopoly on China's drugs sales data.

Alibaba Health's share price dropped to a two-year-low of HK$3.34 (42 cents) after a large Hunan province-based drugstore chain, Yontinhe Group, filed a lawsuit against the China Food and Drug Administration, alleging it had "forced" all drug manufacturers, wholesalers, retailers, and medical establishments in the country to use Alibaba's electronic drug monitoring system.

The system, the Drug Electronic Regulation Platform, was introduced by the administration, but is operated exclusively by Alibaba Health.