Aerosols raise hopes of quick medicinal fixes

May 12, 1995

Diabetics dependent on insulin and patients who receive post-operative pain killers by injection will be the first beneficiaries of pharmaceutical research at Cardiff University.

Pharmacist Steve Farr is working in partnership with Californian pharmaceutical company Aradigm of San Francisco to improve the efficiency of inhalers, so that mouth aerosols can be used to deliver drugs currently administered by injection.

Asthmatics and sufferers of chronic bronchitis have long used inhalers to alleviate lung disease. But Dr Farr and the Californians want to use the lung to introduce a wide range of other drugs from analgesics to insulin. They reckon this can be done if suitable inhalers are used to deliver them.

"The lung offers ideal conditions for absorbing drugs," says Dr Farr. "It has a permeable membrane, a vast surface area the size of a tennis court. As blood passes through it to obtain oxygen, drugs can be easily absorbed into the bloodstream."

But before introducing new drugs by inhaler Dr Farr has had to fight nature. Lungs were designed to keep foreign particles out rather than in, so any drugs have to overcome nature's filtering system located at the back of the throat. This is the reason that when asthmatics use inhalers, they have to coordinate their medication with their breathing. If they breathe too fast, or fail to press the inhaler the second they start breathing in, their lungs receive very little medication.

Sometimes the amount is as low as 10 per cent, because up to 90 per cent of the drug can get lost at the back of the throat.

To overcome this problem Dr Farr and Aradigm have turned to electronics. Their solution is a chip-controlled inhaler.

"Slightly larger than conventional inhalers this battery operated device contains a microprocessor and a transducer in addition to the drug," Dr Farr explains. "The transducer monitors the patient's breath flow and, when this reaches the optimum level, the microprocessor releases the medication. As a result, far more of the dose will penetrate into the lung because very little will be lost on route in the throat."

Dr Farr is spending much of this year in California refining the inhaler's technology and exploring which other drugs could be administered this way.

He expects that the new inhalers will become commercially available within three years, and that they will be used initially to administer analgesics in British and American hospitals.

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