The New Democrats challenged the minister to release the documents during testimony Thursday before the House of Commons trade committee.
NDP trade critic Don Davies told Fast that Canadians have a right to the information so they can evaluate the deal, which was agreed to in principle by Canada and the European Union last month.
"Mr. Davies, we are not going to provide you, or the public with information that is speculative in nature" the minister said. "The information we've been provided is speculative …"
A report last month by two university researchers estimated the cost to Canadians from delaying introduction of cheaper generic medicines will likely range between $800 million and $1.65 billion, once the patents on new drugs expire starting in 2023.
Fast said the government can cushion price shocks.
"We're confident that the impact on the costs of medicines in Canada will be mitigated by steps that we can take."
The minister's remarks echoed past comments by Prime Minister Stephen Harper that Ottawa would consider compensating the provinces if their drug costs end up climbing because of the deal.
Government officials maintain Canadians won't see any evidence of rising costs for at least eight years.
In later testimony, Canadian chief negotiator Steve Verheul told the MPs it would be difficult to predict what additional costs could result from the extended patent protection because there is no way of knowing what new drugs will be produced. He said if "blockbuster" drugs are developed, there would likely be additional costs to provincial drug plans.
Verheul added that the level of compensation required for cheese producers is also difficult to predict, but that the government is committed to "fully compensate" for loss of revenues due to expected increased competition from Europe.
On the overall deal, the negotiator said Canada has an agreement that will be a model for future negotiations and one that the U.S. will have difficulty matching in their talks with Europe. On the issue of provincial government procurement, he noted, U.S. states are unlikely to open their bidding contracts to European contractors, so Canadian firms will likely enjoy preferential treatment in the EU.
Verheul also said the agreement improves on previous deals in the controversial investor protection dispute mechanism that allows firms to sue governments. He said the CETA version will help weed out frivolous cases before they get to litigation, is more transparent and makes clear that governments retain the right to pass laws to protect the environment.
In a later meeting with representatives of medical patient groups, Fast said the deal represents a "balance" between improving intellectual property protection that could drive new research in Canada and controlling drug costs.
Durhane Wong-Rieger of the Canadian Organization for Rare Disorders said she supports the extension of patent protection because Canada has been "slipping" in terms of conducting clinical trials.
"Sometimes when you are talking about life-threatening diseases, it makes a difference when a patient gets into clinical trials because by the time that drug comes to market, that patient could be dead," she said.