Chronotherapy

Chronotherapy is the practice of aligning medical treatment with the body's circadian rhythms to maximize efficacy and minimize adverse effects. Biological processes such as metabolism, DNA repair, immune function, and cell division show 24-hour cycles governed by the circadian clock, with a master clock in the brain's suprachiasmatic nucleus and peripheral clocks in tissues.

In cancer care, chronotherapy delivers chemotherapy at times when malignant cells are more vulnerable and normal tissues are less sensitive to toxicity, a strategy called chronomodulated therapy. Early regimens tested drugs like 5-fluorouracil and platinum compounds on circadian schedules. Evidence is mixed; some trials report reduced toxicity, but others show no clear survival advantage, and routine adoption varies by institution.

Chronotherapy also informs treatment of cardiovascular, respiratory, and inflammatory conditions. For example, timing antihypertensive drugs to blunt nocturnal blood pressure rise or aligning corticosteroid dosing with symptom peaks. The field extends to chronopharmacology, which studies how drug pharmacokinetics and pharmacodynamics vary with time of day.

Implementation relies on assessing circadian phase and chronotype, using markers such as dim light melatonin onset or sleep–wake patterns, and may involve light exposure, meal timing, or specialized drug-release schedules. Individual variability and adherence challenges limit universal recommendations.

Overall, chronotherapy is supported in a limited set of indications and remains an active research area requiring further trials to define benefits and risks.