London, Sept 20 : HP, known for inkjet printer cartridges, has developed a "microneedle" patch that injects medicines painlessly through the skin from a patch on the arm.

The body’s fence against infection is the top layer of skin, called the stratum corneum, which is only a fraction of a millimeter thick, but conventional needles pass far beyond this into a layer called the dermis, which contains nerves, which send a pain message when disturbed.

The new device has tiny needles that push drugs into the skin but do not go far enough under the skin to trigger the pain receptors that are found approximately three-quarters of a millimeter under the skin surface, thereby making takers feel as if they have only been "licked by a cat".

At present, the only substance that the patch is able to deliver is nicotine as it has smaller molecules than other drugs. These drugs need to be pushed past the top skin layer using a needle.

HP has licensed Irish biotechnology firm Crospon to develop the "microneedle" patch for human use and said that it would probably take three years for it to be available to patients.

HP’s patch contains 150 microneedles and the firm says that the dose and even the time of day a drug is injected could be controlled using a microchip.

John O'Dea, Crospon's MD said that another advantage of the HP-developed patch was its potential to carry more than one drug at the same time.

"We think we can deliver both insulin, and glucagon - which counteracts the effects of insulin - which would be of great benefit to diabetics, as one of the greatest risk they face is an overdose of insulin," the BBC quoted him, as saying.

However, Professor Brian Barry, from the University of Bradford asked for a proof to show that people using the new device will not be more exposed to infections.

"The manufacturers would have to demonstrate that making lots of small holes in the skin wasn't letting bacteria and viruses in and causing infection," he said.

"Certainly there is a lot of potential for microneedles, but you also wonder whether it will end up costing too much to deliver a drug which costs pennies," Barry added. (With inputs from ANI)