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Chapter 1: Neural Sciences
tolerability in rodents over the course of the day. Much of this
difference is attributed to circadian variations in the body’s
ability to absorb, distribute, metabolize, and eliminate toxic
compounds. These four processes are affected by underlying
circadian rhythms in physiological processes such as daily
variations in gastric pH, gastrointestinal mobility, glomerular
filtration rate, and membrane viscosity. The rhythmic intake of
food during traditionally timed meals also influences how ther-
apeutic drugs are handled by the body. It is becoming clear that
to maximize efficacy and minimize toxicity of drugs, the circa-
dian phase of administration must be considered. Appropriate
circadian timing of the administration of multiple drugs can be
a daunting challenge to infirmed individuals or their caretakers.
The development of small implanted programmable pumps that
can be directed to administer anticancer drugs or other thera-
peutics at particular times of day may provide a limited solution
to this challenge. The emergence of the field of chronotherapy
is a reflection of our increased understanding of the impact of
the circadian system on the effectiveness of pharmacological
treatments.
R
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