Needle-free device could deliver powdered drugs

"You'll just feel a sharp sting..." No, don't look away, because these words may soon be a thing of the past. A needleless device that jets medicine through the skin could bring an end to painful injections. It could also provide developing countries with a way to deliver powdered drugs, which do not require refrigeration.

There are several needleless systems already on the market, which use explosive forces to eject a liquid drug through a narrow opening at pressures high enough to penetrate the skin. However, they are designed to eject the drug in an "all or nothing" fashion, releasing the same amount of medicine to the same depth every time.

To counter this limitation, Ian Hunter and Nora Hogan at the Massachusetts Institute of Technology, together with Andrew Taberner at the University of Auckland, New Zealand, developed a device based on a "Lorentz force" mechanism.

This consists of a coiled wire that is wrapped around a powerful magnet at one end and attached to a piston at the other. When a current is applied to the wire it interacts with the magnet, pushing the piston forwards. This in turn pushes a liquid drug through a hole the width of a mosquito's proboscis and into the skin. The force can be controlled by varying the current applied to the coil, which allows precise control over dose and depth.

Targeted drugs

Because existing needleless devices offer less control they generally deliver less of the drug to the target site. In some cases, say Hunter's team, just 10 per cent of the drug reaches the correct tissue. Their tests in animal tissue showed that the new device delivers more than 80 per cent of the drug to the target.

The team is now working on adding a vibratory mechanism to their device to allow it to transform powdered drugs into a form suitable for injection. "If you vibrate a powder the drug crystals jiggle around, become energised and behave in a similar way to a fluid," says Hunter.

If successful, their device could help increase the availability of drugs in the developing world, because powdered drugs are more stable than liquid drugs at room temperature ? liquid drugs must be refrigerated to keep them stable. "It's early days but we're pretty excited," says Hunter.

Journal reference: Medical Engineering & Physics, DOI: 10.1016/j.medengphy.2011.12.010

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