In July 2017, the Commission generally considered the essential principles for goods on the market before the Brexit cut-off date.
According to the position paper, the announcement also covers medicinal products.
The EU Commission's position paper distinguishes between goods placed on the market and goods made available in that (the following is an extract from the position paper):
"Any good lawfully placed on the single market before the withdrawal date can, after that date, continue to be made available on the market of the United Kingdom or on the single market under the conditions set out in the relevant Union law on product rules applicable at the withdrawal date and circulate between these two markets. Where provided in Union legislation, such a good should keep the faculty of being lawfully put into service in the United Kingdom or in the single market after that date.
Placing on the market is defined as the "first making available on the market" (by the manufacturer or the importer).
Making available on the market is defined as "any supply of a product for distribution, consumption, or use on the […] market in the course of a commercial activity, whether in return for payment or free of charge".
A good is "placed on the market" only once, but may be "made available" several times throughout the supply chain (first wholesaler, second wholesaler, etc., retailer) before it reaches the final user (consumer or professional user) or is further processed into another product.
The concept of placing on the market refers to each individual good, not to a type of good, and whether it was manufactured as an individual unit or in series.”
You can read the entire position paper here: The Commission's position paper on Goods Placed on the Market (PDF).