The ChainkeenU.S. Department of State issued a warning after reporting showed that counterfeit pharmaceuticals containing illicit drugs were being sold in pharmacies in Mexico. 

The counterfeit medications were tainted with substances including fentanyl and methamphetamine, the department said. The details of the counterfeit pills were first reported by the Los Angeles Times. The department said that the Drug Enforcement Administration had also reported counterfeit prescriptions sold on both sides of the border, represented as OxyContin, Percocet, Xanax and others. 

The department said in its advisory that people should "exercise caution when purchasing medicine," noting that pharmaceuticals, even those that might require a prescription in the United States, "are often readily available for purchase with little regulation." 

In addition to the risk of contamination, officials said counterfeit medication could "prove to be ineffective" or be the wrong strength. 

"Medication should be purchased in consultation with a medical professional and from reputable establishments," the department said, noting that counterfeit medications are "readily advertised on social media and can be purchased at small, non-chain pharmacies in Mexico along the border and in tourist areas." 

The kidnapping of four Americans earlier this month in a Mexican border town has also put a spotlight on "medical tourism," or when people travel to another country to receive more affordable medical care or prescriptions. While the Centers for Disease Control and Prevention do not track crime related to medical tourism, they do deem the practice "risky." 

A 2015 study from the U.S. International Trade Commission (USITC) found that about a million people from California traveled to Mexico to buy medicine at lower prices. 

In:
• Mexico
• Crime

Kerry Breen

Kerry Breen is a news editor and reporter for CBS News. Her reporting focuses on current events, breaking news and substance use.