FDA logoFDA has sent warning letters to four companies for illegally marketing honey-based products with unlisted active drug ingredients found in the erectile dysfunction drugs Cialis (tadalafil) and Viagra (sildenafil).

The agency confirmed the presence of contaminants in the products through laboratory testing.

The agency sent the warning letters to the following companies:

FDA warned of similarly tainted products in April.

The FDA has asked the above companies to provide responses within 15 working days and a plan for how they will remedy the issue. Companies that fail to satisfy the FDA’s concerns quickly may face legal action, including product seizure or injunction.

In February, the agency released an advisory that several herbal supplements sold on Amazon were tainted with tadalafil and sildenafil, which are examples of phosphodiesterase type 5 (PDE5) inhibitors.

Tadalafil and sildenafil could cause dangerous drops in blood pressure when combined with prescription nitrates like nitroglycerin, isosorbide dinitrate and isosorbide-5-mononitrate, vasodilators commonly used to treat and prevent angina. Some physicians have warned that using nitrates together with erectile dysfunction drugs can lead to cardiovascular collapse.

“Tainted honey-based products like these are dangerous because consumers are likely unaware of the risks associated with the hidden prescription drug ingredients in these products and how they may interact with other drugs and supplements they may take,” said FDA Associate Commissioner for Regulatory Affairs Judy McMeekin. “Products marketed with unidentified ingredients may be dangerous and, in some cases, deadly to consumers. We encourage consumers to remain vigilant when shopping online or in stores to avoid purchasing products that put their health at risk, and instead seek effective, FDA-approved treatments.”

A June 2022 study published in the Annals of Internal Medicine, however, found that there was no statistically significant association between the co-prescription of nitrates with PDE5 inhibitors and the risk for outcomes including cardiac arrest, myocardial infarction, angina pectoris, and ischemic stroke and syncope. Another study published in 2021 in The Journal of Sexual Medicine reached similar conclusions.

Early reports in the 1990s and 2000s associated the drug Viagra with hundreds of deaths but noted that a cause-and-effect relationship had not been established.

Many medical professionals warn of the potential drug-drug interactions associated with combining PDE5 inhibitors and nitrates.