Drugs companies in Wales have been distracted from creating new medicines as they are "wasting" time and money preparing for a no-deal Brexit, industry representatives have said.
The UK government wants pharmaceutical firms to stockpile an extra six weeks' worth of medicine in case of a no-deal.
Talks with the EU are currently deadlocked over the Irish border.
Those companies in Wales said "robust plans" were in place but money could be better spent on drugs.
"The deadlock is a challenge for the industry," said Dr Richard Greville, the Welsh branch director of the Association of the British Pharmaceutical Industry (ABPI).
"Because of the global nature of the industry, the supply, the frictionless movement of goods is absolutely critical because some medicines are manufactured in the UK, some medicines are manufactured in the EU and some medicines are manufactured in the rest of the world.
"But, basically, if you are a patient in Wales who needs access to that medicine no matter where it's been manufactured you want the access to that medicine to be unrestricted."
If Downing Street reaches an agreement with EU negotiators in Brussels in the coming weeks and a deal is accepted by the House of Commons, then the UK will leave the EU on 29 March, 2019, but continue to follow Brussels' rules up until the end of 2020 as part of a so-called "transition period".
But businesses are also preparing for a breakdown in the talks and a no-deal Brexit.
Mr Greville said businesses are spending as much as £100m preparing for Brexit.
82 million packets of drugs
"It would be a great pity if it was entirely wasted but perhaps, more importantly, the waste would perhaps have been best spent in developing and creating new medicines, which would have been of far greater use to patients across the world," he added.
About 45 million packs of medicine go from the UK to Europe every month and 37 million packs travel in the other direction.
They need to be licensed, tested and certified by qualified staff and, as it stands, a test in the UK is valid in the EU and vice versa, but that would not be the case in the event of a no-deal.
Two companies based in Wrexham are looking to set up extra bases in Ireland to test and distribute UK-produced drugs to the EU.
Nick Davies, who runs the French-owned Ipsen's site where 400 people work, said: "Brexit is a distraction for the organisation and for the UK pharmaceutical industry and setting-up parallel laboratories in Ireland to repeat testing that we're doing in the UK already can definitely be seen as wasted resource.
And Sirjiwan Singh, the managing director of Wockhardt UK, which supplies generic drugs to the NHS, said: "Doing all the activities two times from a regulatory, licensing and all that mechanisms, that is going to have a major impact on us."