The Intraject delivers a single shot of liquid under pressure through a tiny hole in its tip. The very fine, high-pressure jet is powerful enough to penetrate the outer layers of the skin and is said to be almost painless.
If effective in the trials, the device could be used to deliver vaccines or other drugs reducing the risks associated with needles which can cause infections and are difficult to dispose of safely. It would also be a boon for people who are have a fear of needles.
Weston Medical, the manufacturer, plans to use the device to deliver a new drug being developed by the pharmaceutical company, Hoffman La Roche, to treat hepatitis C which requires patients to have weekly injections. It also plans to use it with a flu vaccine.
A spokeswoman for the company said Intraject had advantages for people who were frightened of injections.
"People who have used say it is like flicking your skin with your fingertip. You feel it but it isn't painful. It also reduces the anticipation of pain which is half the problem with needles," she said.
The device, about the size of a marker pen, contains a pressurised gas container which is used to drive the medicine through the skin into the fatty layer of subcutaneous tissue below.
The safety band is removed and the device pressed against the skin triggering release of the gas which forces the medicine out in a fine high pressure jet. Once it has penetrated the outer layers of the skin, it spreads out in the subcutaneous layer leading to improved absorption.
Larger, needle-less injectors have been used in the past and over the past 50 years there have been 300 patents applied for, according to the company. But it claims this is the first lightweight, pre-filled, disposable version that is simple to use.
However, its price, estimated at 60-75 pence a shot, is almost 10 times the cost of a disposable syringe which could rule out its widespread use by the NHS for the foreseeable future.
The spokeswoman said: "It is a lot because they are very cheap but you have to consider its benefits. It may be possible for patients to use it themselves at home so there is no need for them to go to the doctor and there is no risk of needle stick injuries."
The British Diabetic Association said it would not be suitable for diabetics, who require daily injections of insulin for life, because the device has to be pre-filled with a fixed amount of drug.
Diabetics require varying amounts of insulin from day to day.