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LEARNING OBJECTIVES

  1. Assess the impact of physiological differences between females and males that influence the exposure and response to medications.

  2. Evaluate sex-based differences that contribute to absorption, distribution, metabolism, and excretion of medications.

  3. List examples of altered clinical responses to medication therapy between females and males.

  4. Evaluate sex-based differences that contribute to adverse medication reactions.

INTRODUCTION

Female and male individuals respond differently to a wide variety of medications. Several behavioral, environmental, and lifestyle differences contribute to the variances in medication response between sexes.1,2 Additionally, biological changes that occur over a lifespan alter the response to medications.1,2 Historically, clinical studies lacked appropriate female representation by mainly including male participants and generalizing the findings to female patients and other underrepresented populations.3,4 Therefore, many therapy recommendations for the management of several diseases are not specifically devised for female patients.

Several underlying factors influence sex-based responses that alter exposure and/or clinical outcomes and adverse medication events. Medication exposure differences between female and male patients are due to sex-based differences in pharmacokinetics (ie, absorption, distribution, metabolism, excretion). Differences in response, without alterations in medication exposure between female and male patients, are due to sex-based differences in pharmacodynamics. The most studied underlying factors are fundamental physiological differences between females and males including sex hormones and genetics. However, lifestyle differences between females and males can also influence the differences in medication response. In this chapter, the underlying physiological differences between females and males will be referred to as sex-based differences; whereas lifestyle and environmental differences between females and males will be referred to as gender-based differences. This chapter will largely explore those physiological differences between females and males that have the greatest impact on sex-based medication responses. Specific examples and descriptions of sex-based differences in the pharmacokinetics and pharmacodynamics will be reviewed.

Patient Case (Part 1)

J.K. is a 21-year-old, female, college junior presenting to your clinic.

Subjective Information

Chief Concern: J.K. is concerned about ‘some weird things’ that have happened to her over the past few weeks.

History of Present Illness: J.K. has a history of obsessive compulsive disorder and anxiety disorder for which she is receiving fluvoxamine 25 mg/day. She has also suffered from insomnia for several years for which she has used over-the-counter (OTC) diphenhydramine and temazepam with limited success. Three weeks ago, J.K. was prescribed zolpidem 10 mg/day for insomnia. On a couple of occasions, that happened about 1 to 2 weeks after taking the new medication, her mother reports that J.K. woke in the middle of the night after apparently sleep walking. On the first occasion she woke up in the backyard of her house (she lives with her parents) at 1 AM sitting in a lawn chair. On the second occasion she walked to her friend’s house in her pajamas, four blocks away, at 1:30 AM. She has no recollection of either ...

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