It is a unique formula patent approved by the state. General drugs have a patent protection period, during which his formula is unique, but after the protection period, other manufacturers can use this formula for free, which is why there are many Liuwei Dihuang pills and many Shuanghuanglian oral liquids on the market.
The drugs with state secret formula can keep their own formula forever and never have to be made public, so there is only one kind of Yunnan Baiyao on the market. This keeps his uniqueness.