Aspirin is one of the most widely used drugs in clinical practice. In addition to good antipyretic and analgesic effects, it also has good effects of inhibiting platelet activation and anti-thrombosis, and can be used as primary and secondary prevention of coronary heart disease and cerebrovascular disease, which is of great significance to prevent and reduce the occurrence and development of acute events of coronary heart disease and ischemic strokes. So when is the right time to take aspirin? 1. Before or after meals? Pre-meal theory Aspirin taken orally can cause strong stimulation to the stomach, plus aspirin itself has the function of maintaining normal blood flow in the gastrointestinal tract, preventing mucosal production and reducing platelet coagulation, gastric mucosal damage is very likely to induce bleeding. In addition, the dissolution of aspirin in the body is slow, and the drug is mostly present in the folds of the gastric mucosa in the form of particles, which leads to the presence of bleeding manifestations, and this kind of bleeding is directly related to the dosage of the drug. Due to the poor vascular elasticity of elderly patients, some of them have vascular sclerosis, so their bleeding rate is higher than normal patients. Therefore, it is best to take the drug half an hour after a meal. Postprandial theory In order to diminish its aggressiveness, the process of making aspirin has been greatly improved, and aspirin enteric tablets have been developed. It is this enteric-soluble tablet that is mostly used in clinical practice today. Most enteric-soluble forms are generally pH-dependent and are essentially insoluble in the acidic environment of the stomach, and only begin to dissolve in the alkaline environment of the intestine when they reach the duodenum. However, if the drug is kept in the stomach for a longer period of time, some of the drug will definitely precipitate out of the enteric coating, thus irritating the gastric mucosa, and the longer the storage time and the higher the pH value in the stomach, the more the drug will precipitate out. Therefore, we should try to reduce the retention time of enteric tablets in the stomach, so take them on an empty stomach with warm water, so that the drug can be emptied into the intestine within a few minutes, reducing the chances of the drug precipitating in the stomach and irritating the gastric mucosa. If taken after a meal, on the one hand, the food eaten is mixed with the drug, prolonging the time of gastric emptying, making the drug stay in the stomach for too long, increasing the possibility of drug precipitation; at the same time, the PH value in the stomach becomes high after eating a lot, which is more likely to lead to drug precipitation. The incidence of upper gastrointestinal bleeding due to enteric aspirin is related to the patient’s age, dose, duration of administration, and history of gastrointestinal disease. Timely treatment with gastroprotective agents can effectively reduce the occurrence of upper gastrointestinal bleeding from enteric aspirin. Therefore, enteric aspirin tablets are most effective when taken on an empty stomach; in general dosage form, they should still be taken after meals or combined with gastric mucosal protectors to reduce the side effects of the drug. 2. Night OR early morning? Nighttime theory 1) During the period from the beginning of sleep at night to the next morning, the body is less active, the blood is sticky, the blood flow slows down, and platelets are easy to gather. This situation is prone to blood clots, so the effect of taking it at night should be better. 2) Research has found that aspirin has a mild effect on lowering blood pressure. For patients with mild hypertension, enteric aspirin can be taken at night when they go to sleep, which dilutes blood viscosity, prevents cardiovascular thrombosis, and controls blood pressure, which has a two-fold therapeutic and preventive effect. Early morning theory Aspirin is rapidly and completely absorbed after oral administration, and the peak blood dose is reached 1 to 2 hours after a single dose. According to the biological clock of the human body, the blood viscosity is higher in the morning from 6:00 to 10:00, and the blood pressure and heart rate levels are also high, which is the high incidence of cardiovascular accidents. Therefore, for the purpose of treatment and prevention of cardiovascular diseases, it is more appropriate to take it in the morning from 7:00 to 8:00. The American College of Chest Physicians (ACCP) evidence-based guidelines for antithrombotic and thrombolytic therapy state that aspirin is best taken in the morning for the prevention of myocardial infarction, stroke, and vascular death, and that aspirin enteric tablets are the best dosage form. Both the nocturnal and early morning theories seek to maximize the effect of the drug by peaking in the morning. The peak time of blood concentration of aspirin and salicylic acid is 10-20 minutes and 0.3-2 hours respectively. Since aspirin enteric tablets are acid-resistant, they do not dissolve in acidic gastric juices but dissolve in alkaline intestinal juices. The absorption of aspirin enteric tablets is delayed compared with regular tablets, and the blood concentration peaks around 3.5 hours. On balance, it is more effective when taken early in the morning. To sum up, aspirin enteric tablets are best taken in the morning on an empty stomach; for ordinary dosage form, they should still be taken after breakfast to reduce the side effects of the drug. Long-term use, the effective blood concentration in the body is relatively constant, in order to form a stable effect.