BANGOR — U.S. Sen. Bernie Sanders recently introduced a bill that would allow Americans to import prescription drugs from Canada. The legislation is intended to curb the costs of prescription drugs.

But it would come with a huge cost. Lawmakers need just look at Maine to see why.

A few years ago, Maine introduced similar legislation that allowed patients to buy drugs from foreign pharmacies. We, too, wanted to provide patients with lower-cost medicines.

It proved to be a big mistake. Instead of getting drugs from Canada, we got dangerous and ineffective counterfeit pills from other countries. Maine’s disastrous experience with counterfeit Canadian drug imports should serve as a lesson to our lawmakers to say no to drug importation legislation.

The globe is awash in counterfeit drugs. The World Health Organization estimates that 10 percent of all drugs worldwide are fake, a number that rises to 30 percent in parts of Africa, Asia and Latin America. Thousands of sites sell these drugs to consumers – in 2014, more than 10,000 websites selling counterfeit drugs were shut down.

Counterfeit drugs can be deadly. Sometimes, they contain dangerous ingredients that kill, but far more often, fake drugs contain no active ingredients at all. Patients take these duds expecting them to have positive effects. But instead, patients only grow sicker. Worldwide, officials estimate that counterfeit drugs kill more than 700,000 people each year.

The United States bans most prescription imports in order to prevent smugglers and counterfeiters from shipping unapproved, unsafe products to American patients and pharmacies. In the early 2000s, the Food and Drug Administration stepped up enforcement of the ban after finding that nearly 90 percent of drug shipments to the United States were not up to par. Many of these illicit shipments contained medications that hadn’t been approved by the FDA. Others had not been shipped at the proper temperatures to prevent spoilage.

Despite law enforcement’s best efforts, some counterfeit drugs still wind up in our drug supply. The FDA warns that medical professionals have injected hundreds of patients with counterfeit cosmetics in recent years. Fake treatments for HIV and cancer also have turned up hundreds of times at American medical practices.

And when counterfeit blood thinners from China made their way into the U.S. drug supply in 2008, as many as 81 people lost their lives.

Mainers experienced these hazards firsthand in 2013. That’s when state lawmakers legalized drug importation from developed countries such as Australia, Canada, the United Kingdom and New Zealand.

Many of the drugs that entered our state were not legitimate. To show how unreliable imports could be, Kenneth McCall, then president of the Maine Pharmacy Association, ordered drugs from Canada Drug Center, an online pharmacy claiming to be Canadian. McCall found that the drugs actually had been manufactured in facilities in Turkey and India. Lab testing found that the supposed “Canadian” medications contained “only a tiny percentage of the active ingredient.”

Worse, some of the imported drugs contained dangerous ingredients. The generic blood thinner Clopidogrel, for instance, was contaminated. It most likely contained methyl chloride, which can damage genetic material and even cause cancer.

There is simply no way to ensure the safety of drugs reportedly coming from Canada. Indeed, Bernie Sanders’ proposed law has no mechanism to stop counterfeiters from shipping fake drugs from developing nations, through a Canadian check station, and then on to America. FDA officials have repeatedly warned that they cannot vouch for the safety of drugs that cross the border. And making matters worse, Canadian officials have said that they would not inspect drugs that pass through Canada en route to America. They only monitor the safety of medicines that are prescribed to Canadian citizens.

Americans would be wise to learn from Maine’s mistake. Drug importation is not a worth risk taking, for in the quest for “cheap” foreign drugs, patients could pay with their lives.