Women are almost twice as likely to be prescribed psychotropic medication as men. Because women are the primary consumers of psychotropic medications, it is important to pay attention to gender differences in the pharmacology of these medications.
Other e-weekly topics have addressed issues related to pregnancy, menopause, and birth control with mental health, so this topic will focus on general differences between men and women, on how psychotropic medications are absorbed and metabolized, and on how side effects can differ based on gender.
Thought should be granted to the sexually dimorphic expression of CYP450 enzymes when prescribing medication. This family of enzymes is responsible for the metabolism of a wide variety of medications, including psychotropics. Finding the right dosage of a psychotropic may be notoriously time consuming, requiring multiple trials and errors. Knowledge about the differences in expression of CYP450 enzymes between the sexes can inform treatment direction and, in many cases, decrease the number of medication trials needed for patient response. 1
Clearly, some of these differences are related to hormonal effects. Differences in a woman’s hormones based on her menstrual cycle can affect her absorption, metabolism and response to a particular medication.
In general, women tend to have more side effects than men to psychotropic medications. Research has shown that women are between 50 and 75 percent more likely to experience side effects to psychotropic medications. They report more weight gain with second-generation antipsychotic medications and antidepressants than men do. They report more EPS side effects with first generation antipsychotic medications, particularly over the age of 50.
Studies have shown that premenopausal women have slower gastric emptying time compared to men, which can lead to a delay in passage of a medication into the small intestine. This can cause slower absorption, delayed peak levels and shorter peak serum concentration of the medication.
Serum levels of medications tend to be higher in women than men, and there are many possible contributing factors. Contributing factors include: females have lower total blood volumes compared to males; while females tend to have a higher percentage of body fat compared to males, the gradual release of lipophilic medications into the blood stream can affect serum levels of medication; and females have a slower clearance of medication through the liver and kidneys. This finding may help explain why women have more side effects to psychotropic medications than men, so an optimal dose for a male may be on the higher side for a female.
To make things more complicated, some of these variables can vary throughout a woman’s menstrual cycle. Examples are total body water volume and gastric emptying time.
While it would be impossible to monitor all of these details when prescribing psychotropic medication, the goal of this article is to make readers aware of the key physiological differences between males and females when it comes to absorption and metabolism of medication which can have a clinical impact.