Women's Race may Determine Dosages

Antibiotic dosages may need adjustment for pregnant women of different races

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(RxWiki News) If a pregnant woman needs azithromycin, a common antibiotic for various infections, her dosage amount may be determined by her race.

Azithromycin, (brand name Zithromax or Zmax), is often prescribed for bronchitis, pneumonia, sexually transmitted infections and ear, nose and throat infections and is among the most commonly used medications among pregnant women.

"Follow all prescription dosages exactly."

Lead author James Fischer, a professor of pharmacy at the University of Illinois at Chicago, and colleagues investigated how azithromycin is absorbed, spread and removed from the body.

The researchers drew blood from 78 women of Asian, Caucasian, Hispanic, Pacific Islander and African American descent. All were being treated for an infection while they were in their second or third trimester of pregnancy, and their results were compared to women receiving treatment for infections who were not pregnant.

The results showed that African American women eliminated the antibiotic at rates similar to those of women who were not pregnant, but the other pregnant women's bodies were less efficient in getting rid of the azithromycin.

The researchers therefore concluded that the bodies of the pregnant women of other ethnicities may have absorbed more of the drug than the non-pregnant women or the pregnant African American women - which means their babies were likely exposed to higher doses as well.

The study did not find any higher risk of birth defects for the babies after their mothers took azithromycin, but Fischer said it's always best to minimize fetus's exposure to any drug when possible.

"Many women need to receive prescription medications while pregnant, and they need to receive a safe and effective dose," Fischer said.

"Drug therapy in pregnant women must take into account the physiological changes accompanying pregnancy," he said. “The changes may require adjusting the dosage to ensure that the desired outcome is achieved and that the mother and fetus are not exposed to excess drug."

He said further studies on how certain drugs are metabolized in the livers of pregnant women could use this one as a starting point.

He also said other factors must be taken into account when determining dosages of medications, such as the fact that pregnant women have weakened immune systems that are less able to fight off infection as easily as when they're not pregnant.

The study appears in the journal Antimicrobial Agents and Chemotherapy. It was funded by the U.S. Food and Drug Administration's Office of Women's Health.

Last Updated:
March 16, 2012