Selling vape juice with Viagra in it is not okay, the Food and Drug Administration says. On Thursday, the agency sent a warning letter to HelloCig Electronic Technology Co. Ltd for brazenly selling e-cigarette liquids that have erectile dysfunction drugs in them.

These ED drugs are not for vaping, FDA commissioner Scott Gottlieb said in a statement. And the vape juices certainly have not been FDA approved, despite the company’s claims, as Ars Technica first reported with a series of perfect puns. (“The throbbing mad agency issued a stiff warning…”)

The letter is part of the agency’s efforts to “crack down on misleading claims and illegal and dangerous e-liquids that may entice youth or put consumers at risk,” the FDA’s Gottlieb said. And it preceded a flurry of letters the FDA sent out on Friday to 21 e-cigarette companies — including the ones behind vapes like Vuse Alto, myblu, Myle, Rubi, and STIG — demanding information about whether they’re marketing their products illegally. “Companies are on notice,” Gottlieb said in another statement on Friday.

The letters did not include Juul, the statement says, because inspectors looked for similar marketing information when they showed up without warning at the company’s headquarters at the end of September. The ongoing crackdown reflects the agency’s shift away from viewing vaping as the lesser of two evils for adult cigarette smokers, and instead acknowledging it as a major problem for kids. “We’ll take forceful steps to stem the youth use, even if our actions have the unwelcome effect of impeding some opportunities for adults,” Gottlieb says. “These are the hard tradeoffs we now need to make.”

One thing the FDA is on the lookout for is whether companies have changed their products or started selling new ones since August 2016 — since doing so without FDA premarket approval would be illegal. The agency is particularly concerned about flavored products because kids like them. “We know flavors are one of the principal drivers of the youth appeal of e-cigarettes and we’re looking carefully at this,” Gottlieb says.

If the FDA does find that companies are breaking the law, the FDA could take a few different actions, such as leveling fines against the companies, or seizing their products. The FDA has also started to look into regulating flavors in e-cigarettes, and the agency has said that it plans to speed up its review of stakeholder comments submitted about the proposed rulemaking.

In today’s statement, the FDA reiterated a warning: right now, e-cigarette products that were being sold before 2016 have been allowed to stay on the market until 2022 while vape companies apply for FDA authorization. But the agency says it may rethink that policy. ”This could mean requiring companies to remove some or all of their flavored products,” according to the FDA — at least, until the FDA says those products can be sold. “We’re committed to doing all we can to reverse the disturbing trends of youth tobacco use, especially e-cigarettes,” Gottlieb says. “I’ll do everything I can to curb the epidemic of youth use.”