One teaspoon of pure caffeine delivers roughly the same amount as more than two dozen cups of coffee. (Courtesy of Center for Science in the Public Interest)

The Food and Drug Administration recently sent warning letters to five distributors of powdered caffeine, saying the products, which are marketed as dietary supplements, present a serious health risk if taken in too high a dose.

The move signals an ongoing effort by federal regulators to rein in sales of the stimulant in its pure form, after overdoses of powdered caffeine resulted in the death of two otherwise healthy young men in Ohio and Georgia last year.

[Slew of caffeinated food products has FDA jittery]

Government officials specifically cited the varied labels and serving sizes listed by the distributors, which they said could lead consumers to misinterpret or imprecisely measure how much to use. The FDA noted in its letters that a single teaspoon of pure, powdered caffeine is roughly equivalent to the amount in 28 cups of coffee. It noted that consuming as little as a teaspoon of the stimulant has been associated with nausea, vomiting, anxiety and heart palpitations, while consuming a tablespoon can result in more serious problems, such as chest pains, irregular heartbeat, seizures and, in some cases, death.

“These products are dangerous and present a significant or unreasonable risk of illness or injury to consumers,” the FDA said in a statement Tuesday. “The difference between a safe amount and a toxic dose of caffeine in these pure powdered products is very small.”

The agency warned the five companies — PureBulk, SPN, Kreativ Health, Hard Eight Nutrition and Bridge City Bulk — that they have 15 days to respond or risk legal action and seizure of their products.

Ronald Rudnick, president of California-based Kreativ Health, said Tuesday that his company plans to cease sales of powdered caffeine. A representative for Bridge City Bulk said in an email that the company is "taking this matter very seriously" and also has stopped selling the product. The Post has contacted the remaining companies for comment.

[FDA report describing deaths sheds light on high-caffeine beverages]

The FDA previously has warned consumers about the dangers of powdered caffeine, which can be found cheaply and easily online. Last year, the agency ramped up its efforts to alert the public about its potential dangers after the caffeine overdose deaths of Logan Stiner, an 18-year-old high school senior in Ohio, and 24-year-old James Wade Sweatt of Georgia, who was newly married and a recent graduate of the University of Alabama at Birmingham.

"I cannot say strongly enough how important it is to avoid using powdered pure caffeine," Michael M. Landa, director of the FDA's center for food safety and applied nutrition, wrote in an online posting last December. "The people most drawn to it are our children, teenagers and young adults, especially students who want to work longer to study, athletes who want to improve their performance, and others who want to lose weight. ... As regulators and parents ourselves, we take this threat to public health very seriously."

Because pure caffeine is sold as a dietary supplement, it faces far fewer regulatory restrictions than traditional pharmaceutical drugs. The FDA said Tuesday, however, that it "continue to aggressively monitor the marketplace" for powdered caffeine and crack down on any violations that it identifies.

The advocacy group Center for Science in the Public Interest said the FDA's warning letters "show progress on the issue, but the agency’s action today falls short of a comprehensive ban and recall of the product. ... Pure caffeine never should have been sold to consumers. A teaspoon is a fatal dose for a child, and two teaspoons would kill most adults. FDA has clear authority to ban such a hazardous product and should do so."