Federal authorities say about 200 patients have developed complications from receiving doses of the injectable form of naltrexone for alcohol dependence, Reuters reported Aug. 12.

An official with Cephalon Inc., which has marketed the medication Vivitrol since 2006, says it appears the complications were the inadvertent result of physicians not properly injecting the drug into muscle tissue. The Food and Drug Administration (FDA) said it has received 196 reports of problems such as swelling, pain and bleeding, with 16 individuals requiring surgery to drain abscesses or to repair tissue.

Vivitrol is injected into a patient's buttocks, and physicians must make sure that the needle is injected past the fat layer and into the gluteal muscle. The FDA said women may be at higher risk of complications from the injections because of "typically higher gluteal fat thickness," adding that most of the Vivitrol patients who needed surgery were women.

The FDA has advised physicians to use care when giving the injections and to ask patients to monitor the injection site for any possible complications.

The Cephalon official said about 70,000 doses of the medication have been shipped since 2006. The injections are given to patients monthly.