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Do Women Experience More Side Effects From Drugs Than Men?

A new study highlights sex differences in reactions to certain medications.

Do women take longer than men to eliminate medications from their bodies? Do women’s kidneys function differently than men’s kidneys? A new study published in Biology of Sex Differences (June 2020) offers some clues.

Erving Zucker and colleagues from the University of California, Berkeley did a search of more than 5,000 publications and focused on 86 drugs given to men and women. At equivalent dosages, 76 out of those 86 drugs had a higher concentration in the blood of women than in the blood of men. In addition, the Berkeley researchers found that almost twice as many women had more adverse reactions to medications than men did.

Zucker’s group even found a study showing that one drug (the anticoagulant Lepirudin) stayed in the blood of women for up to 48 hours, whereas the anticoagulant stayed in the blood of men for just two hours. This could potentially explain why women experienced many more adverse side effects to that drug than men.

Why Might Women Experience More Drug Side Effects Than Men?

One possible explanation is that women usually have less body weight than men. But even if a man and a woman are the same weight and receive the same dose of a drug, there could be differences in drug concentrations in the blood of men and women. Why could this be?

Zucker cites previous studies that show that:

  • Women’s stomachs usually take longer to empty than men's and women's stomach pH is generally more acidic.
  • Women’s organs are typically smaller than men’s (important in case of liver elimination of drugs where a woman’s liver is typically smaller and has less blood flow than a man’s liver).
  • Women’s kidneys eliminate drugs slower than men (smaller glomerular filtration rate)
  • Women have less blood plasma volume which will result in more concentrated drug doses.
  • Women tend to have more fat than men which can influence drug metabolism.
  • And of course, women have cyclic hormone variations which can also affect drug metabolism.

So, the difference of metabolism between men and women can result in women being drug-overdosed compared to men.

Are Women the Only Ones at Risk of Being Overdosed?

The answer is no.

Out of the 86 drugs studied, Zucker et al found that seven had a higher concentration in the blood of men but only two of those drugs gave men adverse reactions.

So, according to Zucker’s studies much more women than men had higher blood drug concentrations and 96% of the women who had higher blood levels of the drugs, had adverse reactions.

Unfortunately, a lot of medications are given at the same dose to men and women, regardless of their weight and sex on a “one-size-fits-all” basis, based on clinical trials done in the past where only male animals were studied and where only male patients were recruited.

Nowadays, for new medications, both men and women are studied in clinical trials, but rarely are sex differences taken into account.

The result is that recommended doses are still often the same for adult men and women.

What Can We Do About These Sex Differences?

In general, you want to take the lowest possible dose of a medication that can achieve the desired result. Thus, if you have adverse reactions from a medication, ask your physician if a smaller dose could allow for the same positive results with fewer problems.


More from Chris Gilbert, M.D., Ph.D.
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