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The US Food and Drug Administration has issued a warning letter to the Canadian company CanaRx for playing a role in “the introduction of unapproved new drugs and misbranded drugs” to the United States, according to the letter.

“These drugs are potentially dangerous to U.S. consumers,” the FDA said in a news release Thursday.

An unapproved new drug has not been approved for use by the FDA. A misbranded drug fails to bear either adequate directions for its intended use or adequate warnings relating to its use.

CanaRx helps residents of the United States purchase medications from pharmacies in Canada, Australia and the United Kingdom, according to its website. Hundreds of the most commonly prescribed brand-name drugs are included in the CanaRx program, according to its website.

Joseph Morris, counsel for CanaRx Services, said in a statement Friday that the FDA’s description of the CanaRx business model is incorrect and that the company should be seen as an ally of the agency’s in the fight for patient safety.

“The CanaRx program does not involve new, experimental, unapproved or misbranded medications. Rather, CanaRx works for individual American patients who wish to exercise their rights of personal importation, as permitted by law and by the FDA’s own handbooks. CanaRx facilitates foreign physicians rewriting of the employee’s valid U.S. prescription, and then supplies the employee with approved versions of FDA-approved drugs that have been sourced from Canada, the United Kingdom or Australia where they have undergone review from those countries’ drug regulatory systems,” the statement says.

“Every prescription that is dispensed through a CanaRx program is dispensed directly to the patient from a licensed, regulated, brick-and-mortar pharmacy in Canada, the United Kingdom, or Australia, and the patient can be sure that the medicine she receives is the medicine the doctor ordered,” it says. “CanaRx believes that the FDA is trying to prevent Americans from being injured by unregulated suppliers of counterfeit and other dangerous substances. CanaRx agrees with the FDA’s goals.”

Some of the drugs received through the program treat hepatitis, cancer or HIV. The FDA letter warns that those are serious medical conditions and that side effects of drugs that may have been recalled, but still obtained through CanaRx, could be life-threatening.

The letter, sent Tuesday, also warns that certain drugs distributed by CanaRx may have different dosage strengths or trade names or be manufactured by different companies from versions of the drug that are FDA-approved and available in the United States.

“Such differences can cause patient confusion and lead to medication errors,” according to the letter, which includes a list of more than 150 websites affiliated with CanaRx.

The warning letter was sent after a “lengthy review” of the drug distributor’s practices, the FDA said.

“When a consumer goes online to buy medicines purportedly from Canada, they may get a medicine sourced from elsewhere that could be counterfeit, expired or misbranded. While operations or illegal online pharmacies may state on their websites that its medicines are coming from Canada, the United Kingdom, Australia, etc., this is not necessarily always the case,” Commissioner Dr. Scott Gottlieb said in the news release.

“Such operations and illegal online pharmacies take advantage of unsuspecting Americans by purporting to distribute safe and effective imported drugs, at least some of which are instead expired, mislabeled, subject to recalls or potentially counterfeit and that are provided outside of the closed American distribution system meant to protect patient safety,” Gottlieb said.

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“Operations like CanaRx use their names to imply that patients are receiving medicines approved in Canada, when it’s likely that patients are receiving medicines from other countries, and which may be sub-potent, super-potent or counterfeit. Importantly, they’re also distributing drugs for which the FDA-approved versions are subject to additional safety requirements,” he said. “These risk mitigation programs are a legal requirement and are in place for important safety reasons. Sidestepping them is unacceptable and puts the safety of patients in great jeopardy.”

The warning letter calls for CanaRx to “promptly cease causing the distribution of unapproved new drugs and misbranded drugs to U.S. consumers and correct all other violations.” The letter also requests that the company respond within 10 working days with details on how such violations have been or will be corrected.

CanaRx said in its statement that it “will respond promptly, fairly and fully to the FDA.”