Dipyridamole is the name given to an active substance from the group of platelet aggregation inhibitors. The drug is used primarily for the prophylaxis of strokes.
What is dipyridamole?
Dipyridamole is the name given to a drug belonging to the group of platelet aggregation inhibitors. The drug is used primarily for the prophylaxis of strokes. Dipyridamole belongs to the group of antithrombotics. The drug is used to prevent the formation of thrombi (blood clots) and thus to prevent strokes. Dipyridamole was first used in 1959. The drug was used to treat coronary heart disease (CHD). In the following years, it was found to have a dilating (widening) effect on the coronary vessels. Eventually, dipyridamole also came into use as a platelet aggregation inhibitor. In modern times, a combination of dipyridamole and acetylsalicylic acid (ASA) is usually used to counteract post-stroke relapses that occur in the setting of cerebral ischemia (TIA). However, a higher benefit of this combination therapy compared to single administration of acetylsalicylic acid is considered controversial among medical experts. According to studies, stroke is 1.47 times more likely to occur with combination therapy than when ASA is administered alone. In addition, side effects such as headache are more common.
Pharmacologic effect
Dipyridamole exhibits the effect of dilating human blood vessels as well as preventing platelets (thrombocytes) from clumping together. This process is also called aggregation in medicine. Through this process, it is possible to prevent constriction or occlusion of blood vessels. Dipyridamole has the property of blocking the transport of the nucleoside adenosine. As a result, the synaptic cleft receives more adenosine. Via G-protein-coupled processes, this leads to relaxation (relaxation) of the muscles, which in turn causes dilation of the blood vessels. Dipyridamole exerts its vasodilatory effect primarily in the coronary vessels. These are responsible for supplying the heart muscle. However, dipyridamole is no longer used today for the prophylaxis or therapy of angina pectoris, since in most cases the coronary vessels automatically dilate to the maximum so that more blood can reach the heart muscle. The use of dipyridamole would also cause healthy coronary vessels to dilate, which increases their blood flow. However, this process causes the diseased vessels to receive less blood, which further increases the deficiency supply to the diseased heart muscle area. Physicians refer to this process as the steal effect. In the blood, dipyridamole binds 99 percent to plasma proteins. Metabolization of the active ingredient takes place via the liver. The average plasma half-life is 40 minutes. Dipyridamole is excreted from the body in the stool.
Medicinal use and application
For use, dipyridamole is usually used together with acetylsalicylic acid to prevent strokes caused by vascular occlusion in the brain. An important area of application for the active ingredient is also medical diagnostics. Dipyridamole is used in myocardial scintigraphy and stress echocardiography. The administration of dipyridamole under controlled conditions, such as blood pressure measurement or ECG monitoring, allows the heart to be stressed by medication. In this way, it is possible to assess blood flow to the heart muscle by single-photon emission computed tomography or wall motion by sonography (ultrasound examination). Dipyridamole is taken orally. For this purpose, capsules are taken daily.
Risks and side effects
In some cases, the use of dipyridamole may cause unwanted side effects. These are primarily drowsiness, headache, pain in the muscles, flushing, nausea, vomiting, rapid heartbeat, redness of the skin, and low blood pressure. Rarely, sufferers also experience worsened angina or hypersensitive reactions such as hives and rashes on the skin. In the context of a surgical procedure, the bleeding tendency may increase.In the case of peridural or spinal anesthesia, it is considered advisable to discontinue dipyridamole 48 hours before the procedure if the substance is combined with acetylsalicylic acid. However, it is possible to continue administration immediately after the procedure. If dipyridamole is discontinued too quickly, there is a risk of angina pectoris attacks and, in the worst case, even a heart attack. Treatment with dipyridamole must not take place if the patient suffers from hypersensitivity to the drug. Dipyridamole therapy must also be withheld in cases of severe heart disease. These include recent heart attacks, severe heart failure, cardiac arrhythmias, angina pectoris attacks, narrowing or obstruction of the aortic valves, uncontrolled disturbances of blood flow, and circulatory failure. During pregnancy, consultation with the treating physician must be made prior to the use of dipyridamole. The same applies to breastfeeding. Dipyridamole is not suitable for children. When using dipyridamole with other drugs, adverse interactions must be taken into account. For example, xanthine derivatives, which include theophylline or the caffeine present in coffee, can weaken the positive effects of the platelet aggregation inhibitor. If dipyridamole is combined with blood thinners such as coumarins, the effect of the drug is enhanced. In addition, the effect of antihypertensive drugs is increased by the administration of dipyridamole.
