Aspirin intake in the morning is associated with suboptimal platelet inhibition, as measured by serum Thromboxane B2, during infarct-prone early-morning hours.

Aspirin is traditionally taken once daily in the morning and considered to be effective throughout the 24h interval. Cardiovascular events occur most frequently in the early morning, suggesting that these hours are critical in terms of adequate platelet inhibition. This study therefore assed platelet function in the early morning-8.00 AM-in healthy volunteers, during a once-daily (OD) 80 mg morning in comparison with an OD evening regimen and a twice-daily (BID) 40 mg regimen. It was an open-label randomized cross-over study, comprising 12 healthy subjects. Subjects were allocated to three sequential dosage regimens: 80 mg OD at 8.00 AM, 80mg OD at 8.00 PM, and 40 mg BID at 8.00 AM and PM. Platelet function 12 and 24 hours after aspirin intake was measured by means of serum thromboxane B2 (sTxB2) levels, the collagen/epinephrine closure time (Platelet Function Analyzer(PFA)-200®) and the Aspirin Reaction Units (ARU, VerifyNow®). The results demonstrated that early morning sTxB2 concentrations were 5843pg in the morning regimen, 2877pg in the evening OD regimen, and 3343pg in the BID regimen (morning- vs evening regimen p = < 0.01; morning- vs BID regimen p = < 0.01). Early morning PFA-closure time (p = 0.12)) as well as VerifyNow ARU (p = 0.17) mean values were similar for all three regimens. In conclusion, the OD-morning regimen seems to acquire the lowest level of platelet inhibition during the critical early morning window. Switching to an OD-evening or BID intake seems prudent, although further research on clinical cardiovascular outcome in patients with stable cardiovascular disease is needed.

Aspirin adherence during high-risk pregnancies, a questionnaire study.

OBJECTIVE: Aspirin reduces the risk of recurrent hypertensive disorders of pregnancy (HD) and fetal growth restriction (FGR). This study examined the non-adherence rates of aspirin in women with high-risk pregnancies. STUDY DESIGN: All consecutive women between 24 and 36weeks gestation with an indication for aspirin use during pregnancy were invited for this study. A survey was used which included two validated questionnaires, the simplified medication adherence questionnaire (SMAQ) and the Beliefs and Behaviour Questionnaire (BBQ). MAIN OUTCOME MEASURES: To determine the non-adherence rates of aspirin, and to identify the beliefs and behavior concerning aspirin. RESULTS: Indications for aspirin use during pregnancy were previous HD, FGR, intrauterine fetal death or current maternal disease. Non-adherence rates according to the SMAQ and BBQ were 46.3% and 21.4% respectively. No differences in demographic background or obstetrical characteristics between adherent and non-adherent women could be demonstrated. CONCLUSIONS: Adherence for aspirin in this high-risk population cannot be taken for granted. The non-adherence rates in pregnant women are comparable with the non-adherence rates for aspirin in the non-pregnant population.

Evening intake of aspirin is associated with a more stable 24-h platelet inhibition compared to morning intake: a study in chronic aspirin users.

Daily generation of novel platelets may compromise aspirin's platelet inhibitory action, especially near the end of the regular 24-h dosing interval. A contributor to this attenuation could be the endogenous circadian rhythm. The primary objective of this study was to assess platelet activity 12 and 24 h after different times of aspirin intake (c.q. 8.00 AM and 8.00 PM). A randomized open-label crossover study was conducted, comprising outpatients with stable cardiovascular disease taking aspirin once daily. We measured platelet aggregation with the platelet function analyzer (PFA)-200(®) and light transmission aggregometry (LTA). The attenuation of aspirin's inhibitory action was most apparent in the 8.00 AM regimen. The platelet function analyzer-closure time was 78 s faster at 24 h than at 12 h after intake in the 8.00 AM regimen (IQR: 166.8-301 vs. 132.8-301; p = 0.006) and 0 s faster at 24 h than at 12 h after intake in the 8.00 PM regimen (IQR: 198.8-837.0 vs. 169.8-301; p = 0.653). The adenosine diphosphate 1.0 µmol/L maximum amplitude was 5.40% higher at 24 h than at 12 h after intake in the 8.00 AM regimen (95% confidence interval (CI): -0.03--10.8; p = 0.040) and was 0.75% higher 24 h than at 12 h after intake in the 8.00 PM regimen (95% CI: -4.83-3.33; p = 0.705). The platelet inhibitory effect of aspirin decreases after 24 h, particularly after intake in the morning. These results suggest that patients might benefit from evening intake or twice daily intake regimens.