Makers of caffeinated energy drinks are squarely in the cross hairs of two senators. But even as Richard J. Durbin of Illinois and Richard Blumenthal of Connecticut finally have the ear of the Food and Drug Administration, 5-Hour Energy continues to be sold right under their noses at a Senate coffee shop as a pick-me-up for congressional staffers and the lobbyists who woo them.

Despite the ubiquity of such energy boosters, the makers of 5-Hour Energy have been caught flat-footed on the lobbying front by Democrats Durbin and Blumenthal as they make an example of them on the Senate floor, demanding stronger regulations of energy drinks amid reports that 18 deaths and more than 100 health incidents have been associated with consumption of the products since 2004.

Companies such as Red Bull North America and Monster Beverage Corp. have relied on trade associations to convince lawmakers that their products are safe. But 5-Hour Energy — the most jacked-up product of them all — does not have a registered lobbyist and has not joined any industry groups. The company seems to have shunned official Washington, relying instead on its omnipresence in stores, aggressive marketing and D.C.’s penchant for late nights.

“We’re just not set up like that here with a government affairs person,” said Elaine Lutz, a spokeswoman for 5-Hour Energy, which is made by the Michigan based-Living Essentials, a private company that reportedly has annual revenue of $1 billion.

In a Nov. 21 response to the two senators released this week, the FDA said it will consider new labeling requirements and health warnings related to such products. “Depending on the outcome of our ongoing review of the safety of ‘energy drinks,’ which includes caffeine alone and in combination with other ingredients, we will take action as needed with respect to the levels of caffeine in these products,” wrote Michele Mital, the acting associate commissioner for legislation at the FDA.

The FDA’s letter, however, took some pressure to elicit. Durbin and Blumenthal sent four letters to the agency in 2012. A Durbin aide said the senators found the original response insufficient, leading to the follow-ups.

Less than a decade ago, the American Herbal Products Association, which represents Monster Beverage Co., lost a battle to protect products containing ephedra. But Michael McGuffin, the group’s president, said caffeine, which is consumed daily by millions of Americans, is different.

“That affects the politics,” he said. “It is highly unlikely that the regulatory approach or the legislative approach to a stimulant that we use every day is going to mirror the stimulant that we don’t.” The AHPA has spent $30,000 lobbying this year.

A 2006 law requires makers of dietary supplements, including 5-Hour Energy, Monster and PepsiCo’s Rockstar, to report to the FDA any adverse effects involving their products. 5-Hour Energy has been associated with 13 deaths since December 2009 and Monster drinks have been associated with five deaths, according to FDA data released earlier this month. Red Bull, a $5.5 billion-a-year company whose product is regulated as a beverage, is not required to report adverse health incidents.

The FDA is in the process of clarifying the distinction between liquid dietary supplements and caffeinated beverages such as sodas.

Red Bull, PepsiCo Inc., the maker of Rockstar and Amp Energy, and Coca-Cola Co., the maker of Full Throttle, already voluntarily report the levels of stimulants, including caffeine and taurine, in their products and discourage use by children under the age of 12 in accordance with American Beverage Association guidelines. So far this year, the ABA has spent almost $1 million lobbying on this issue and others.

5-Hour Energy does not disclose the level of caffeine in its products, but a Mayo Clinic analysis found it to be 207 mg for each 60 ml shot. A 16-ounce brewed coffee from McDonald’s contains 100 mg of caffeine, while a can of Red Bull or Monster contains about 80 mg. Lutz declined to comment on the data.

The company’s spokeswoman also dismissed the senators’ concerns about the effect of high levels of caffeine consumption among young people. “That is so irrelevant to us because we don’t market to children,” she said. “You’re not looking at skate boarders going on the half pipe. You’re looking at construction workers. Primarily it’s adults, with that 2:30 [p.m.] feeling.”

Industry lobbyists argue that the deaths reported by the companies were merely coincidental and were not caused by consumption of the products themselves. They say energy drinks are unfairly targeted for caffeine content while coffee drinks that contain just as much, or more, caffeine are ignored.

The FDA reported in August that caffeine intake for healthy adults of up to 400 mg per day “is not associated with general toxicity, cardiovascular effects, effects on bone status and calcium balance (with consumption of adequate calcium), changes in adult behavior, incidence of cancer, or effects on male fertility.” The FDA has also noted that it has not determined whether the health incidents linked to energy drinks were actually caused by consumption.

That has not deterred Durbin and Blumenthal from taking on the issue. “Let me show this 5-Hour Energy picture. … Everyone is pretty familiar with it because they are everywhere — literally everywhere. I watched on television last week when they were advertising promotions of 5-Hour Energy drinks saying, in the commercials, that some of the sales would go to promote research for breast cancer,” Durbin said, referring to an ad campaign for a pink-lemonade-flavored version. “There is almost the suggestion there is something healthy about this product.”