Obesity reduces injection efficacy

Drugs are less effective when they are injected into larger bottoms and longer needles could be needed to help drugs reach their target, according to new research.

A team of doctors from the Adelaide and Meath Hospital in Dublin found overweight patients had so much flesh on their buttocks that injections could not reach the muscle and were therefore less effective.

They found that overweight women were more likely than any other group not receive full dosage because of their fleshy bottoms.

The Dublin researchers studied 50 patients who needed an intramuscular injection in their bottom before receiving a scan.

Each patient was given an injection which contained a tiny air bubble that would enable researchers to follow the progression of the medication to the muscle.

In men 56 per cent of injections reached their intended site while only eight per cent hit the spot in women, suggesting that longer needles are needed for bigger bottoms.

Lead researcher, Dr Victoria Chan, 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.”

Dr Chan said that many of her patients were receiving little, if any, effect from buttock-administered injections because of weight issues.

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

The bottom is the preferred site of injection for many drugs such as painkillers, vaccines, contraceptives and anti-nausea drugs since there are few major blood vessels, bones and nerves that could be damaged by a needle.

Also, the muscle underneath the layer of fat on the bottom has rich supply of tiny blood vessels which can effectively absorb the medicine.

Injections administered to the bottom are also a popular choice for patients who cannot take drugs orally.

Dr Chan also said that if the medication did not reach its intended site, it could remain in the fatty tissue where it could cause local infection and irritation.

The findings were presented to a conference of the Radiological Society of North America.

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