The Food and Drug Administration sent letters to eight companies and individuals yesterday warning them to stop offering products such as "Space Cadet Capsules" and "Druids Fantasy Capsules" as alternatives to street drugs.

The agency said it has been investigating products, promoted as legal dietary supplements, being marketed as drug alternatives. Some of the drugs contain ephedra, which is legal but cannot be sold as an alternative to street drugs.

The products are not dietary supplements under the legal definition because they are not meant to be used to augment the diet, promote health or reduce disease risks, the agency said.

Last fall the agency stopped imports of an herbal product promoted as an alternative to illegal street drugs and informed operators of an Internet site selling "Yellow Jackets" they were breaking the law.

The FDA has shut down previous ephedra sellers who marketed the herb as a legal alternative to cocaine and other illegal drugs, saying dietary supplements cannot be marketed in that way.

Ephedra is popular for weight loss and bodybuilding, so long as the street-drug claim isn't made. Even legal ephedra is highly controversial, however, and has been linked to dozens of deaths. Some critics have asked the FDA to ban ephedra, and the government has begun a criminal investigation into whether a U.S. manufacturer lied about the herb's safety.

The FDA said Monday's action came after it studied the firms' Web sites, which it said promoted the products for recreational purposes.

Companies and individuals sent warning letters were Cherokee Naturals, Woodstock, Ga.; Ecstasy Melrose, Los Angeles; Mark Hurlbut, Glendale, Ariz.; John Hoover, Edinboro, Pa.; Jason Pacey, Peoria, Ill.; Brian Petruzzi, Margate, N.J.; Shaun Roberts, Tampa; Stardust Industries, Northridge, Calif.