For the millions of diabetics and other patients who need to self-inject drugs daily with painful needles, reliable skin patch devices-similar to the ones ex-smokers use to get their nicotine fix-would be a great relief. The trick is finding ways to push large-molecule drugs, like insulin and human growth hormone, through the skin's oily top layers. An Israeli company believes it has a promising solution: radio waves.

TransPharma Medical of Yehud, Israel, has developed a handheld device that administers a blast of radio frequency energy to scrape away the top layer of skin cells. This produces channels about 50 micrometers wide that allow drugs from a patch to work their way into the bloodstream. "Of the methods used to open up channels through the skin to allow bigger molecules to be delivered, this company's approach sounds the most promising," says Gordon Flynn, professor of pharmaceutical science at the University of Michigan. That's because the device-which has met with success in initial studies-opens pores for a whole day with minimum discomfort, sterilizes them, and adjusts for different skin types, Flynn says.

Still, TransPharma hasn't proven its technology in human trials. Chief executive officer Daphna Heffetz says that within a few months, the company will begin clinical trials of a patch for people suffering from human-growth-hormone deficiencies. The company is conducting studies with four pharmaceutical companies to determine the feasibility of the approach with insulin and other drugs. "It looks interesting, but it is still early stage," says Samir Mitragotri, a chemical engineer at the University of California, Santa Barbara, and a cofounder of Sontra Medical of Franklin, MA.

There's plenty of competition. Sontra, for example, is developing an approach that uses ultrasound. "There is a place for more than one technology in the market. I think each viable technology will find its niche," says Mitragotri. Whichever versions succeed, they could create a $5.7 billion market by 2009 in the U.S. alone, says Ajit Baid, analyst at the research firm Frost and Sullivan.