Side Effects, Sex Effects


“Side effects include internal bleeding, kidney disease, liver failure, and death.” As many pharmaceutical commercials indicate, side effects can be cause for serious alarm.

Adverse effects from medication don’t affect everyone equally. Women report side effects two times as often as men and are more likely to end up in the hospital because of a serious medication-related complication.

Sex differences in drug processing may be the culprit. On average, males and females have different hormones, organ size, and gastric pH, and each of these factors affect the absorption and distribution of drugs. Very few drugs that process differently by sex are due to sex differences in height, weight, and body composition. Of the 31% of drugs that process differently by sex, almost all move more slowly through female bodies. This means females tend to be exposed to higher amounts of drugs for longer periods of time.

Zucker and Pendergast found that 96% of drugs that take longer for females to process than males are indeed associated with more side effects in women. Few drugs take longer for males to process than females, but the researchers found those drugs did not cause more side effects in men than women.

Though men and women now participate in clinical trials in similar numbers, the pharmaceutical industry still has steps to work towards gender equity.


Morphine serves as a good example. The anaesthetic is prescribed to males and females in similar doses. Morphine processes more slowly through female bodies than it does through male bodies, so females who take morphine are exposed to higher doses for a longer period of time than males who take the drug. Women who take morphine are about 1.5 times as likely as men to experience side effects, including respiratory depression and hypoxia, nausea, and vomiting.

How did we get here? Why are most drugs administered in one-size-fits-all doses when male and female bodies process many drugs differently?

In 1977, the Food and Drug Administration (FDA) barred virtually all women from participating in clinical trials in the name of preventing birth defects. In 1993, the FDA reversed the misguided recommendation and encouraged trials to include women and people of color. But many drugs on the market today were approved by the FDA before the guideline change, so they were only tested on men. By making male bodies the default for drug processing, the FDA likely harmed more women than they protected.

Though men and women now participate in clinical trials in similar numbers, the pharmaceutical industry still has steps to work towards gender equity. Clinical trials for new drugs often don’t report effectiveness or side effects by sex, and the FDA does not publish this information for older drugs. New trials should be required to report drug processing by sex, and the FDA should publicly publish this data. This minor change could facilitate corrective dosing measures and minimize side effects for women and gender minorities.

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