The U.S. Food and Drug Administration (FDA) has warned consumers not to purchase or use Neptune's Fix, a supplement dubbed "gas station heroin," following reports of seizures and loss of consciousness associated with it.

Neptune's Fix, a product sold illegally with claims to improve brain function and treat conditions such as anxiety, depression, pain and opioid use disorder, contains a potentially dangerous substance called tianeptine.

"FDA has received severe adverse event reports after the use of Neptune's Fix products, including seizures and loss of consciousness leading to hospitalization. Consumers who experience a bad reaction to any tianeptine product should seek immediate medical help," the agency said in a news release.

People may mistake tianeptine as being safe and effective as it is easily available across gas stations and vape or smoke shops. However, it is an unapproved drug associated with serious health risks and even death, the officials warn.

"Tianeptine is not approved by the U.S. Food and Drug Administration for any medical use. Despite that, some companies are illegally marketing and selling products containing tianeptine to consumers," the FDA said.

However, the drug is approved for use in some countries where people use it as an opioid alternative, or for self-treatment of anxiety or depression. There have been reports of increased addiction and withdrawals associated with tianeptine, similar to opioid toxicity and withdrawals.

The reported side effects include agitation, drowsiness, confusion, sweating, rapid heartbeat, high blood pressure, nausea, vomiting, slowed or stopped breathing, coma and death.

According to the Poison Control Center in the U.S., there has been a stark increase in cases of tianeptine abuse nationwide, from 11 cases between 2000 and 2013 to 151 cases in 2020.

Neptune's Fix's labels indicate the presence of tianeptine in the product. Authorities warn there could be other harmful ingredients as well as they conduct tests to identify them.

Consumers are requested to avoid the use of all products that contain tianeptine and report adverse events or side effects associated with them to the FDA's MedWatch Safety Information and Adverse Event Reporting Program online.