The expanding size of people's bottoms is presenting doctors with a new medical challenge: how to get injectable drugs to where they are needed.
Injections given in the buttocks are unlikely to work because patients bottoms are too fat, researchers said yesterday. For drugs to be effective, injections must be delivered into muscle which is supplied with microscopic blood vessels, to maximise absorption of the medicine. But the larger size of the average backside means the muscle is now covered with a layer of fat and the standard needles fitted to syringes are not long enough to penetrate it.
Researchers gave injections with a tiny air bubble to 50 men and women and then observed what happened using a CT scanner. They found that only 32 per cent of the injections reached the muscle. In men just over half the injections were successful but in women only 8 per cent were.
Injectable drugs including painkillers, contraceptives and anti-nausea medication, have traditionally been given in the bottom because it offers a substantial pad of soft tissue.
Victoria Chan, from the Adelaide and Meath Hospital in Dublin, Ireland, 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."
The findings were delivered in Chicago yesterday to a meeting of the Radiological Society of North America. Dr Chan said the study did not directly show less of the drug was being absorbed but it strongly suggested that was the case.
Drugs companies had designed their drugs so that the proper dosage was absorbed into the bloodstream from the muscle and if it was injected into fat tissue less of it would be absorbed. The answer, she said, was to use longer needles when injecting into the buttocks.