Drug injections miss the mark in obese patients

Patients with large behinds do not derive the biggest benefit from vaccines and other injections into the buttocks, according to a study by Dr. Victoria Chan and colleagues at the Adelaide and Meath Hospital in Dublin, Ireland.

Researchers observed 60 obese men and women scheduled for CT scans of the abdomen and pelvis who had received intramuscular medication. They found that 68% of intramuscular injections did not reach the buttock muscles.

The overall success rate of the injections was 32%. The success rate among men was 56% compared with only 8% among women. Compared with men, women typically have a higher amount of fat in their buttocks.

"The amount of fat tissue overlying the muscles exceeds the length of the needles commonly used for these injections," Chan said at the 2005 RSNA meeting.

Her solution? Longer needles.