Biotech, pharma and medical device companies might not have much to worry about in the immediate term amid Britain's decision to bow out of the European Union, but those with major overseas exposure to the region, such as Pfizer (PFE) - Get Report and Merck (MRK) - Get Report , could suffer down the line in the case of an economic downturn or should the UK adopt its own rules and regulations, according to at least one industry expert. 

"Right now, the only immediate impact is potential foreign currency exposure, but I don't think we'll see an immediate impact on sales," Jeffrey Loo of S&P Global Market Intelligence said. 

"Longer term, a lot of economists expect a 0.5% to 1% decline in GDP in the U.K. and potentially in the EU, so we may see softer sales in Europe," Loo said. 

Besides Pfizer and Merck, a report by Loo cited Bristol-Myers Squibb (BMY) - Get Report , Celgene (CELG) - Get Report , Amgen (AMGN) - Get Report and Medtronic (MDT) - Get Report as companies that could face negative implications following Brexit given their European exposure, noting that it is estimated to take two years for the U.K. and EU to determine how the change will take place. 

"Pfizer is so huge and have pretty sizable exposure in Europe, so a downturn there could hurt sales," he noted.

Europe accounted for about $9.71 billion, or close to 20%, of Pfizer's $48.85 billion in total revenue in 2015.  

In comparison, Europe accounted for about $6.7 billion, or about 23% of Medtronic's total sales of $28.83 billion for is fiscal 2016 year ended April 29. 

There is also risk associated with how intellectual property rights, quality standards and clinical trial rules will change, if at all, as a result of Brexit, noted Loo. 

As things currently stand, approvals for drugs and medical device products are currently uniform across all 28 EU countries.

While the U.K. would now be free to come up with its own rules and regulations, Loo suspects industry groups and lobbyists would push for UK regulators to continue to harmonize all related protocols.

Another change we'll see in connection with Brexit the relocation of the EMA, or European Medicines Agency, which is currently located in London. The EMA could move to Paris, noted Loo, who suspects the change might cause the UK to have less influence on European health care debates. 

"The risks are a little more perceived risks than natural risks," Loo said.