More than 2,600 drugs have some stage of manufacture in Britain and 45 million patient packs are supplied from the UK to other European countries each month, while another 37 million flow in the opposite direction, drugmakers said on Thursday.
Brexit threatens the free flow of these goods, given stringent medicine regulations that will require the retesting of drugs shipped across borders in the absence of an agreed trading arrangement.
The European Federation of Pharmaceutical Industries and Associations (Efpia) said a survey of its members showed 45 percent of companies expected trade delays if Britain and Europe fell back onto World Trade Organization rules after Brexit.
Drugmakers also face an additional hurdle when it comes to licensing their products, since more than 12,000 medicines will require a separate UK licence in order for them to be prescribed.
"For life-saving and life-improving medicines, the EU and UK cannot afford to wait any longer to ensure that the necessary cooperation on medicines is in place from the day the UK leaves the EU," said Efpia Director General Nathalie Moll.
Pharmaceutical companies have insisted since last year's Brexit referendum that a comprehensive agreement is needed to ensure maximum alignment between EU and British pharmaceutical regulations.
But with the clock ticking down to Brexit in March 2019 with no sign yet that a trade deal will be concluded, many companies are drawing up detailed procedures to protect drug supply chains.
AstraZeneca's (>> AstraZeneca) chief executive, Pascal Soriot, said his company was working on additional systems for quality control and release of products after manufacturing.
"What we are doing now is duplicating this process, so that we can release goods in Europe that have been manufactured in the UK," he told reporters after the company announced its quarterly results on Thursday.
GlaxoSmithKline (>> GlaxoSmithKline) also said last month it was preparing a system to test drugs inside the European Union if Britain crashes out of the bloc without a trade deal.
(Reporting by Ben HirschlerEditing by Toby Chopra, Greg Mahlich)
By Ben Hirschler