Pharmacy shelves are full of medications that can be prescribed to men or women. But most people are not aware that all drugs do not work the same for men as they do for women. Some medications need to be prescribed in different doses for different sexes, and some medications that work well for one sex may not work at all for the other.
Pharmacokinetics is the study of how drugs travel into, through, and out of the body. Pharmacodynamics considers what the drug does to the body while it is there. This combination of factors determines how much of a drug is available to the body, how well it will get to the desired location in the body, how effectively it will work, and how long the effects will last. For example, a drug that is injected directly into a blood vessel will become effective in the body much faster than a drug that is swallowed as a pill and must first be digested before it can work.
One of the considerations in both pharmacokinetics and pharmacodynamics is the sex of the patient receiving the drug. For many years, drug testing was conducted only on men. Researchers reasoned that women should not have the risk of drug testing during their childbearing years since men and women are basically the same. Doctors were taught that the only adjustment needed for women vs. men in prescribing drugs was to account for the differences in weight. New research has revealed that men and women can react very differently to medications, beyond the differences caused by body size.
Most medications, whether over-the-counter (OTC) or prescription, are taken by mouth. This means the medication must first be digested by the stomach or intestines before it can enter the blood stream. For example, some drugs including certain antibiotics need stomach acid in order to reach the state where the body can make use of them.
Researchers now know that men tend to have steady levels of stomach acid while acid levels in women are lower much of the month except in the middle of the menstrual cycle. This can affect how well a woman’s stomach can absorb certain medications.