AUSTIN (KXAN) — The U.S. Food and Drug Administration is telling people not to buy nine over-the-counter supplements available at various online retailers because of undeclared ingredients in them.

All nine drugs are marketed and promoted for “sexual enhancement“, the FDA said. All the drugs have either sildenafil, the active ingredient in the FDA-approved medication Viagra, or tadalafil, the active ingredient in the FDA-approved medication Cialis.

The FDA said the use of those medications is “for use under the supervision of a licensed health care professional.” The agency also said the drugs could potentially interact with nitrates found in some prescription drugs, like nitroglycerin. It could lower blood pressure to “dangerous” levels, the FDA said.

The FDA issued the warnings Dec. 8.

The FDA pointed out all the drugs are sold on Walmart’s website, but also said they could also be sold in other retail stores.

The OTC drugs the FDA advises against are:

The FDA said it “identified an emerging trend where over-the-counter products, frequently represented as dietary supplements, contain hidden active ingredients that could be harmful.”