Pregnant Women's Medication Needs Varies

NEWS RELEASE
For immediate release

Contact:  Rebecca Lentz, College of Pharmacy, 612.624.7654
              Sara E. Buss, Academic Health Center, 612.624.2449

PREGNANT WOMEN’S MEDICATION NEEDS VARIES, STUDY SAYS
Findings to help determine drug dosages in pregnant women

MINNEAPOLIS / ST. PAUL (Feb. 15, 2005) -- Findings from a University of Minnesota study will help pregnant women get the right dose of medication to successfully manage chronic conditions such as diabetes, depression, or HIV.

A pregnant woman’s ability to metabolize medications depends on the stage of pregnancy and the medication taken, and dosages can’t be determined by a one-size-fits all approach, said Timothy Tracy, Ph.D., a College of Pharmacy professor and lead author on the study. The findings were published in the February issue of the American Journal of Obstetrics and Gynecology.

“We’re talking about treating the mother’s chronic condition,” Tracy said. “We’re talking about determining what’s the right dose of medication at what stage of pregnancy. The question is: Are we getting the right dose to treat her condition?”

Among the most commonly prescribed medications for pregnant women are antidepressants, antipsychotics, codeine-based pain relievers, antivirals for treatment of diseases such as HIV, blood pressure medications, and certain antibiotics.

Most medications do not have dosing guidelines for pregnant women. Dosing guidelines for drugs—including those commonly used in pregnancy—are based on studies conducted on men. The drug studies that involve women use only women who aren’t pregnant.

Researchers knew pregnant women needed to have their medications adjusted, but they didn’t know by how much and whether to increase or decrease those dosages. The findings from the study show that those changes depend on the stage of pregnancy and the medication given.    

“You can’t treat all medications the same,” Tracy said. “You can’t say ‘She’s pregnant so we automatically have to increase or decrease the medication.’”

As more women have children later in life, the number of women using medications to manage chronic conditions will increase, Tracy said.

“The bottom line is if a pregnant woman has a chronic condition, she needs the medication,” Tracy said. “Her asthma didn’t stop because she got pregnant. Her depression didn’t stop because she got pregnant. The pregnancy didn’t address the underlying, chronic biological imbalance.”

In the study, pregnant women were given two drugs known to be safe during pregnancy. The drugs were caffeine and a dextromethorphan, a cough suppressant, which is available without a prescription.

Pregnant women were given the drugs three times: Between the 14th and 18th weeks, between the 24th and 28th weeks, and between the 36th and 40th weeks of pregnancy. They were also given the drugs between six and eight weeks after birth.

There are three enzymes in the body that metabolize about 80 percent of medications—including caffeine and dextromethorphan. Tracy studied the concentration of the drugs after they were ingested to determine whether metabolism of medication increased or decreased throughout pregnancy.

Tracy found pregnant women’s metabolism of some medications increases or decreases only once, while metabolism of other medications continues to increase or decrease as pregnancy progresses. The change depended on which enzyme the body used to metabolize the drug.

Researchers can now correlate the findings to the 80 percent of medications metabolized by these enzymes.

“The dose a woman needs in pregnancy may need to be changed throughout her pregnancy,” he said.

The College of Pharmacy, the only school of pharmacy in Minnesota, offers its program on the Twin Cities and Duluth campuses. Founded in 1892, the College of Pharmacy educates pharmacists and scientists and engages in research and practice to improve the health of the people of Minnesota and society. The college is part of the Academic Health Center, which is home to the University of Minnesota’s six health professional schools and colleges as well as several health-related centers and institutes.

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