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Monday, June 22, 1998 Published at 16:18 GMT 17:18 UK


'This won't hurt at all'

Injections with large needles could soon be a thing of the past

Scientists have developed 'microneedles' which could improve the effect of medications and deliver them without any pain.

The needles, which are much thinner than a human hair, do not hurt because they penetrate only the outermost layer of skin that contains no nerve endings.

Produced using techniques originally developed for the microelectronics industry, the tiny needles could also allow the development of new therapeutic compounds and open the door for microprocessor-based systems for delivering drugs continuously or in response to the body's needs.

Researchers at the Georgia Institute of Technology believe their microneedles would be especially useful with large protein-based molecules, such as those produced through new biotechnology processes.

Impractical or unpleasant

Such drugs often cannot be taken orally, but must be administered frequently enough to make traditional needle injection impractical or unpleasant.

Dr Mark Prausnitz, assistant professor in Georgia Tech's School of Chemical Engineering, said: "We envision microneedles being 'user-friendly' for patients, similar to the current transdermal patches that are in common use."

"We expect in its final design that a microneedle array would be quite easy to use. Patients would just peel a liner off and stick it onto the skin. They would not see any needles, and there should be no pain associated with it."

The first use for the microneedle arrays would be for one-time injections.

Left attached to the skin

However, Dr Prausnitz believes the arrays could also be left attached to the skin to provide continuous administration of medication under the control of microprocessor-based equipment.

[ image: Diabetics could beneBBCfit]
Diabetics could beneBBCfit
"This system could provide constant communication between the drug reservoir and the inside of the body," he said.

"Using a microprocessor to control a pump would allow the device to be programmed to deliver a drug at variable rates. The pump could also be controlled by the patient or a clinician."

If microneedle arrays were also used to withdraw bodily fluid for analysis, the microprocessor-based equipment could automatically administer drugs based on the body's need.

Such a feedback system would be useful in regulating the blood sugar levels of persons suffering from diabetes, said Dr Prausnitz.

Researchers have so far built solid silicon microneedle arrays 10 millimetres square. The existing needles are 150 microns long and leave holes about one micron in diameter when removed from the skin.

Reduce infection

Further development could reduce the length and diameter of the microneedles, make them hollow to increase the rate of drug delivery, and permit mass fabrication of arrays at least a centimetre square. If the diameter of the microneedles can be reduced, the holes they produce could be small enough to exclude bacteria, eliminating a potential source of infection.

Most drugs now are delivered orally, or through injections. To be orally administered, drugs must resist decomposition in the body's gastrointestinal tract, be readily absorbed through the intestinal wall, and survive attacks by enzymes in the liver. Conventional hypodermic needles get drugs directly into the bloodstream, but cause pain, create the potential for infection, and require medical training to use.

A limited number of compounds, such as nicotine, can be readily absorbed by the skin. Techniques are being developed for improving transdermal drug administration using chemicals, electricity and ultrasound to make the skin more permeable.

Significant improvement

But through limited laboratory testing, the researchers claim they have have demonstrated that their microneedles can significantly increase absorption of a drug compound through the skin by as much as 25,000-fold.

Once the microneedles penetrate the outer layer of skin known as the stratum corneum, they can carry medications into deeper areas of the skin where the compounds diffuse, are absorbed by capillaries and carried into the bloodstream.

Before the microneedles could be used to administer drugs to humans, the researchers must demonstrate their safety and effectiveness through extensive animal and human testing.

Dr Prausnitz said potential problems could arise if high levels of drug under the skin cause local inflammation, or if the body reacts to the needle material itself. There is also a risk of the needles breaking off in the skin.

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