FDA is the US Food and Drug Administration. It does not accept or approve patents and has nothing to do with patents. Do you mean by restrictions: Are there any restrictions on the production and sales of drugs patented in the United States by our domestic companies? That's what it means.
If a product has not applied for a patent in China and been authorized, or has applied for an international patent but has not been formulated to enter China or has not been authorized domestically, then we can imitate it. But now large international companies have a strong awareness of patents, especially for developing countries like ours. They usually apply for patents in our country, so there are almost no loopholes mentioned above.