When we take a medication, we expect it to have a specific result in our bodies. Some drugs are designed to reduce pain, relieve inflammation, reduce allergy symptoms, or kill harmful bacteria. How effective a drug will be is determined in part by how well the body is able to use the drug, which is the result of drug metabolism.
Drug metabolism basics
When we take a medication, whether by injection or by swallowing it, our bodies have to interact with the drug in order to get the intended benefit from it. Many drugs are chemically altered by enzymes in the body to activate them. This process of chemically changing a drug is called drug metabolism.
Most drugs are metabolized by the liver using a specific group of enzymes called P-450. Researchers have learned that men and women have differences in the type, concentration, and activity levels in their P-450 enzymes. They believe this disparity is caused by variations in how men and women produce growth hormone.
Growth hormone levels
In women, growth hormone production happens at a steady rate and maintains a consistent level. In men, growth hormone production is regulated by the hormone testosterone which results in highs and lows in growth hormone levels. These different levels mean that men and women metabolize drugs at different rates, which can affect how well drugs work and how long they remain functional in the body.
Monthly hormone cycles
Women tend to have more active enzyme systems which means some drugs are metabolized and removed from the body faster than in men. Because some drugs interact with the hormones progesterone and estrogen, women may also react differently to these drugs than men do. In addition, a woman’s own reaction to the medication may change as she goes through her monthly cycle.
For example, the drug Dilantin, which is used to treat epilepsy, may be metabolized differently at different points in a woman’s menstrual cycle. Women may tend to have seizures just before or at the start of their period because increased levels of the hormone progesterone at that time of month boosts the ability of the enzymes to metabolize Dilantin, which removes it from the body at a faster rate than happens at other times of the month. Hormone replacement therapy (HRT) can also affect how drugs are metabolized. Women taking anticoagulants such as warfarin (Coumadin) need to be carefully monitored if they are also taking estrogen because higher estrogen levels may allow the warfarin to work more effectively.
Doctors who recognize these hormonal differences in how men’s and women’s bodies use different drugs can compensate for hormonal fluctuations by instructing their patients to take different doses of the medication at different times in the monthly cycle.
Sources:
Merck Manuals
Legato, Marianne J., M.D. Eve’s Rib New York: Harmony Books, 2002. Print.