Research Article
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Published Online: 2 February 2005

Biological Rhythms, Medication Safety, and Women's Health

Publication: Journal of Women's Health
Volume 14, Issue Number 1


Biological processes and functions in women are well organized in time, as evidenced by the expression of ultradian (high frequency), circadian (∼24-hour), circamensual (∼monthly), and circannual (∼yearly) rhythms and by the changes that occur with menarche, reproduction, and menopause. Attributes of women's circamensual structure have been explored in depth, particularly with regard to fertility/infertility and birth control. However, the role of 24-hour and other rhythms in health, disease, and treatment has been little studied. The symptom intensity of a variety of chronic medical conditions is rhythmic, as is the risk of severe events, such as stroke and myocardial infarct (MI). Improving the safety, efficacy, and preventive qualities of medications requires the understanding of how rhythms impact drug pharmacokinetics and pharmacodynamics. The therapeutic and adverse effects of prescription and nonprescription medications widely used by women can vary markedly with the (circadian) time of administration. Circadian rhythm-dependent differences in the safety of medications are particularly relevant to pregnant women; laboratory animal studies show that the fetal toxicity of various treatments varies not only with developmental stage but also with circadian time. Rhythm-dependent differences in the actions of medications are also of great importance to perimenopausal and postmenopausal women, who are advised to ingest prescribed pharmacotherapy for osteopenia and osteoporosis in the morning to minimize the risk of adverse effects and, as a consequence, may elect to take other medications at times not recommended in the instructions for their use. Medication trials must be comprehensive and representative of women and men of different life stages, ethnicities, and likely times (morning vs. evening) of drug use.

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cover image Journal of Women's Health
Journal of Women's Health
Volume 14Issue Number 1January/February 2005
Pages: 38 - 46
PubMed: 15692276


Published online: 2 February 2005
Published in print: January/February 2005


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    Michael H. Smolensky
    The University of Texas–Houston School of Public Health, Health Science Center, Houston, Texas.
    Ramon C. Hermida
    E.T.S.I. Telecomunicación, Bioengineering and Chronobiology Laboratories, Campus Universitario, Vigo, Spain.
    Erhard Haus
    Health Partners, Department of Pathology, St. Paul, Minnesota.
    Francesco Portaluppi
    University of Ferrara, Hypertension Center, Department of Clinical and Experimental Medicine, Ferrara, Italy.
    Alain Reinberg
    Foundation A. de Rothschild, Equipe de Recherches, Chronobiologie Humaine, Paris, France.

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