Gender is just one factor in how patients respond to drugs

December 1, 2006

Research has provided more support for the idea that differences do exist between the sexes. Since 2001, the interest seems to have waned. Called pharmacokinetics, it is the study of what the body does to a drug, not what the drug does to the body.

Five years ago was prime time to explore the ways in which men and women react to certain drugs-research that has provided more support for the idea that differences do exist between the sexes. Since 2001, the interest seems to have waned. Called pharmacokinetics, it is the study of what the body does to a drug, not what the drug does to the body.

In 2001, The Institute of Medicine: published a report, "Exploring the Biological Contributions to Human Health; Does Sex Matter?" which says that sex must be considered in all aspects and at all levels of biomedical research because sex does matter.

Four of them-Posicor to treat hypertension, antihistamines Seldane and Hismanal, and Propulsid for gastrointestinal problems-indicated more adverse effects in women when the drugs were widely prescribed for both genders. The report hypothesized that "greater health risks for women may be due to physiological differences that make women differentially more susceptible to some drug-related health risks."

Seldane, Hismanal and Propulsid induced fatal cardiac arrhythmia in some women, perhaps because of a women's QT level, the time it takes for the heart to relax after it contracts when pumping out blood, while male sex hormones moderate the heart muscle's sensitivity to these drugs, says the GAO.

And of course, who could forget the hoopla in 1997 surrounding the combination of fenfluramine and phentermine-fen/phen-which posed serious health risks for women?

Research has exposed a variety of reasons for the differences in gender response to certain drugs, including lower body weights in women, differences in absorption, metabolizing and elimination of drugs by the body and the effects of liver enzymes and sex hormones. Among the results of these mechanisms are that often more serious side effects are suffered by women than men, more women develop life-threatening ventricular arrhythmia after taking a variety of drugs and women wake up from anesthesia faster than men.

In addition, women are consuming more medications than men, including herbal remedies, over-the-counter medications and vitamins.

Heidi Law, director of clinical programs for Costa Mesa, Calif.-based Prescription Solutions, a pharmacy benefits manager (PBM), says that gender differences in response to drugs are not a major issue for her organization. "It's not that we don't recognize that it exists," she says. "If the differences were that important, the FDA would have made some recommendations on dosing and labeled drugs accordingly. Gender, along with genetics, height and weight, age and whether a person smokes or consumes alcohol, is just one of many factors that affect the way people respond to drugs."

Law adds there is such a large therapeutic index-the ratio of the drug dose which produces an undesired effect to the dose which causes the desired effects used as a measure of the relative safety of the drug for a particular treatment-that there is no need to stipulate different dosing levels.

Although Prescriptions Solutions might not address gender differences related to drugs, it is concerned with developing health initiatives by gender, such as programs directed at women on hormone replacement therapy and osteoporosis and treatment of benign prostatic hyperplasia for men.