"Our study has demonstrated that a majority of people, especially women, are not getting the proper dosage from injections to the buttocks," said lead author Victoria O. Chan, M.B., registrar in the clinical medicine department of The Adelaide and Meath Hospital in Dublin, Ireland.

"There is no question that obesity is the underlying cause," Dr. Chan said. "We have identified a new problem related, in part, to the increasing amount of fat in patients' buttocks."

Many medications are administered through injections into the muscles of the buttocks, including painkillers, vaccines, contraceptives and anti-nausea drugs. The upper, outer quadrant of the buttock is the preferred site for intramuscular injections, because there are relatively few major blood vessels, nerves and bones in this region that could be damaged by the needle. Yet the rich supply of microscopic blood vessels in muscle speeds drug absorption into the system.

Intramuscular injections are a common alternative when patients cannot swallow oral medications, are fasting for a procedure or have a metabolic disorder that inhibits the absorption of orally ingested medication. The use of intramuscular injections has increased over the past 10 years, and new medications have been developed for delivery in this way. However, Dr. Chan's research has demonstrated a majority of these injections are largely ineffective.

"Our study has shown that 68 percent of intramuscular injections do not reach the muscles of the buttock," Dr. Chan said. "The amount of fat tissue overlying the muscles exceeds the length of the needles commonly used for these injections."

Pharmaceutical companies design medications so that the proper dosage is absorbed into the blood stream from the muscle. Becaus
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Contact: Maureen Morley
mmorley@rsna.org
630-590-7762
Radiological Society of North America
28-Nov-2005