Injections may fail for fat people

Jan 24, 2006

INJECTING drugs into the buttocks of fat people may not be a reliable way of administering medicine, research suggests.

INJECTING drugs into the buttocks of fat people may not be a reliable way of administering medicine, research suggests.

Doctors from a hospital in Dublin found many patients had so much fleshy tissue on their buttocks that jabs could not properly penetrate to the muscle.

They found that women, especially obese ones, were most likely not to get the full dose.

Lead researcher Dr Victoria Chan, based at the Adelaide and Meath Hospital, said, “Our study has demonstrated that a majority of people, especially women, are not getting the proper dosage from injections to the buttocks. There is no question that obesity is the underlying cause.”

Many medications are administered through injections into the muscles of the buttocks, including painkillers, vaccines, contraceptives and anti-nausea drugs.

Good site

The buttock is the preferred site because it contains relatively few major blood vessels, nerves or bones that could be damaged by the needle, but the underlying muscle has a rich supply of microscopic blood vessels, which can absorb medicines effectively.
The use of injections has increased over the past 10 years.
However, Dr Chan’s research found that 68% of the injections do not reach the muscles of the buttock.

She said, “The amount of fat tissue overlying the muscles exceeds the length of the needles commonly used for these injections.”

Companies design medications based on the assumption that they are injected straight into the muscle. Injections, which only reach into the fat tissue, will not deliver as much medication, as the tissue contains significantly fewer blood vessels.

Chan said patients were either not receiving the maximum benefit of a drug or receiving no benefit at all.
Furthermore, if the medication is not absorbed into the blood stream, it remains in the fatty tissue where it can cause local infection and irritation.

The research focused on 50 patients due to undergo abdomen or pelvis scans. Each was given an intra-muscular jab, which contained a small air bubble, so the researchers could track the path of the medication.

Only 56% of injections successfully reached muscle tissue in men, while in women, the success rate was just 8%. Women have more fat in their buttocks than men.

Vaccine problem
Professor Richard Guy of Bath University, told the BBC News website the effectiveness of vaccines could be compromised.

They tend to be made up of large molecules that would only slowly diffuse out of fat tissue.
He said, “Whether using longer needles is a practical solution, I’m not sure, as these are unlikely to be terribly popular. A better approach might be to give the intra-muscular injection where there is less fat around.”

Professor Guy said alternative technologies, such as micro needles, were under development, which can deliver drugs into the blood vessels underlying the skin.
He said obesity was doubtless a factor but it was also important to use the right length of needle and to ensure that those who administered jabs used proper techniques.

BBC

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