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Last Updated: Wednesday, 19 September 2007, 11:15 GMT 12:15 UK
Patch promises painless injection
Patch
The 'patch' contains tiny needles
Technology from inkjet printer cartridges could be used to inject medicines painlessly through the skin from a patch on the arm.

The device uses a system patented by HP to push drugs through tiny needles, which do not go far enough under the skin to trigger pain receptors.

It could potentially deliver many drugs currently injected or taken daily.

However, one expert said proof was needed that people using them will not be more vulnerable to infections.

HP has licensed Irish biotechnology firm Crospon to develop the "microneedle" patch for human use.

How the patch works

It said that it would probably take three years for it to be available to patients.

At present, only substances which can be absorbed directly through the skin, such as nicotine, can be delivered using a patch.

The majority of drugs, which contain bigger molecules, can't do this, and must be pushed past the top skin layer using a needle.

Tough layer

The top layer of skin, called the stratum corneum, is the body's barrier against infection.

This is only a fraction of a millimetre 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 manufacturers would have to demonstrate that making lots of small holes in the skin wasn't letting bacteria and viruses in
Professor Brian Barry, University of Bradford

These receptors are found approximately three-quarters of a millimetre under the skin surface, but the microneedles should only reach approximately half a millimetre at most, passing the stratum corneum without hitting the dermis.

There are 150 microneedles in a patch, and HP says that the dose and even the time of day a drug was injected could be controlled using a microchip.

John O'Dea, Crospon's Managing Director, said that another benefit of the HP-developed patch was its ability 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," he said.

Infection worry

Professor Brian Barry, from the University of Bradford, is a leading researcher into new methods of delivering drugs through the skin.

He said that having a microneedle patch applied to your skin would feel like being "licked by a cat", but not painful.

However, he said that anyone developing this technology would have to overcome several hurdles before it was ready for patients.

He said: "The stratum corneum is the layer of skin that keeps your insides in, and the outside world out, and it's perfectly designed for this.

"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.

"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."


SEE ALSO
Jet injection to aid cancer fight
10 Sep 07 |  Northern Ireland
Skin patch hope for Parkinson's
07 Apr 06 |  Health

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