Two British inventors have teamed up to build and market PowderJect, a needleless method of delivering solid-form drugs and other substances into patients. High-pressure helium enters a chamber when the device is activated. At the end of the chamber is a cartridge holding the powdered drug between two plastic membranes. The membranes rupture when pressure reaches a predetermined point, letting the gas expand and create a shock wave. The wave travels down a nozzle at between 2,000 and 3,000 ft/sec. Behind the wave, the gas carries the drug particles and accelerates them to about 2,400 ft/sec. When the gas and particles leave the nozzle and hit the skin, momentum lets the drug penetrate the skin while the helium gas is reflected into a silencer. "It offers a much gentler form of injection," says Paul Drayson, one of the inventors. "As well as being needle-free and painless, it avoids needle-stick injuries, and, more importantly, shoots medications to a precise layer of skin, in some instances improving the effect of the drug."