The U.S. Food and Drug Administration (FDA) has issued a recall for Duro Extend Capsules for Men, a product intended to treat erectile dysfunction.

According to an FDA press release, government analysis of the capsules found that they contained sulfoaidenafil, an analogue of sildenafil.

Although sildenafil is an FDA-approved drug, its analogue is not. The FDA release states that sulfoaidenafil “may interact with nitrates found in some prescription drugs (such as nitroglycerin) and may lower blood pressure to dangerous levels.”

Officials also warned that people suffering from diabetes, high blood pressure, high cholesterol or heart disease may take nitrates. All these conditions are potential risk factors for erectile dysfunction.

Men suffering from erectile dysfunction who are concerned about potential side effects of Duro Extended Capsules or other medications may be interested in trying constant resistance rings to help them achieve and maintain an erection.