Aspirin - bedtime or morning administration

• acetylsalicylic acid (aspirin [ASA]) is a non-steroidal anti-inflammatory drug (NSAID) with demonstrated inhibitory effects on cyclooxygenases (COX), responsible for arachidonic acid metabolism and prostaglandin production
• many variables related to the regulation of BP, previous results have demonstrated a predictable circadian variation in plasma renin activity, angiotensin II, catecholamines, atrial natriuretic peptides, aldosterone, and angiotensin-converting enzyme
• in addition to the action on arachidonic metabolism, ASA has been shown to have various other effects including a time-dependent effect on levels of angiotensin II (1)
• there is evidence that patients with mild hypertension receiving aspirin treatment before bedtime showed a significant reduction in blood pressure compared to those taking their aspirin in the morning (1)
  • in the patients who received aspirin before bedtime the reduction in blood pressure observed during a 3 month study was 6.8/4.6 mm Hg in systolic/diastolic BP (p < 0.001)
  • benefits of bedtime administration of aspirin, in terms of blood pressure lowering, has been previously demonstrated in other groups including pregnant women (2)

Reference:

1. Hermida RC et al. Aspirin administered at bedtime, but not on awakening, has an effect on ambulatory blood pressure in hypertensive patients. J Am Coll Cardiol. 2005 Sep 20;46(6):975-83
2. Hermida RC et al. Administration-time dependent influence of aspirin on blood pressure in pregnant women. Hypertension 2003;41: 651–65