echocardiography when it causes ischemia. Flow heterogeneity (a necessary precursor to ischemia) can be detected with gamma cameras and SPECT using nuclear imaging agents such as Thallium-201, Tc99m-Tetrofosmin and Tc99m-Sestamibi. However, relative differences in perfusion do not necessarily imply any absolute decrease in blood supply in the tissue supplied by a stenosed artery. Other uses Dipyridamole also has non-medicinal uses in a laboratory context, such as the inhibition of cardiovirus growth in cell culture. Drug interactions Due to its action as a phosphodiesterase inhibitor, dipyridamole is likely to potentiate the effects of adenosine. This occurs by blocking the nucleoside transporter (ENT1) through which adenosine enters erythrocyte and endothelial cells. According to Association of Anaesthetists of Great Britain and Ireland 2016 guidelines, dipyridamole is considered to not cause risk of bleeding when receiving neuroaxial anaesthesia and deep nerve blocks. It does not therefore require cessation prior to anaesthesia with these techniques, and can continue to be taken with nerve block catheters in place. Overdose Dipyridamole overdose can be treated with aminophylline or caffeine which reverses its dilating effect on the blood vessels. Symptomatic treatment is recommended, possibly including a vasopressor drug. Gastric lavage should be considered. Since dipyridamole is highly protein bound, dialysis is not likely to be of benefit. Mechanisms of action Dipyridamole has two known effects, acting via different mechanisms of action: Dipyridamole inhibits the phosphodiesterase enzymes that normally break down cAMP (increasing cellular cAMP levels and blocking the platelet aggregation, response to ADP) and/or cGMP. Dipyridamole inhibits the cellular reuptake of adenosine into platelets, red blood cells, and endothelial cells, leading to increased extracellular concentrations of adenosine. Experimental studies Dipyridamole is currently undergoing repurposing for treatment of ocular surface disorders. These include pterygium and dry eye disease. The first report of topical dipyridamole's benefit in treating pterygium was published in 2014. A subsequent report of outcomes in 25 patients using topical dipyridamole was presented in 2016. References Adenosine reuptake inhibitors Ethanolamines Antiplatelet drugs Phosphodiesterase inhibitors 1-Piperidinyl compounds Pyrimidopyrimidines Stroke