To the Editor.
—Two recent articles suggested that the inhibition by aspirin of thromboxane synthesis and cyclooxygenase-dependent platelet aggegation protects women against a first myocardial infarction1 and pregnancy-induced hypertension.2 So far, little if any attention has been paid in clinical trials to the timing of aspirin administration. Perhaps some individuals may take aspirin at a convenient time, but when the drug is inactive.Results shown in the Figure from a small sample of women suggest (with statistical significance) not only that low doses of aspirin affect prostaglandin and adrenergic pathways but also that such effects vary as a function of the circadian stage at which the aspirin is taken. Six clinically healthy women aged 20 to 30 years volunteered to participate in a randomized pilot study that consisted of a reference stage (which lasted 2 days starting after a 5-day adjustment to hospital conditions) followed by a 7-day
Cornélissen G, Halberg F, Prikryl P, Danková E, Siegelová J, Dusek J. Prophylactic Aspirin Treatment: The Merits of Timing. JAMA. 1991;266(22):3128-3129. doi:10.1001/jama.1991.03470220044018