This inhibition causes an increase in intracellular sodium levels, resulting in decreased activity of the sodium-calcium exchanger, which normally imports three extracellular sodium ions into the cell and transports one intracellular calcium ion out of the cell. The reversal of this exchanger, triggered by the increase in intracellular sodium, results in  an increase in the intracellular calcium concentration that is available to the contractile proteins. The increased calcium concentrations lead to the binding of more calcium to troponin C, which results in increased inotropy. Increased intracellular calcium lengthens phase 4 and phase 0 of the cardiac action potential, which leads to a decrease in heart rate. Increased amounts of Ca2+ also leads to increased storage of calcium in the sarcoplasmic reticulum, causing a corresponding increase in the release of calcium during each action potential. This leads to increased contractility (the force of contraction) of the heart without increasing heart energy expenditure.The inhibition of the sodium pump may also improve baroreceptor sensitivity in heart failure and may explain some of the neurohormonal effects of digoxin.Digoxin also has important parasympathetic effects, particularly on the atrioventricular node. While it does increase the magnitude of myocardial contractility, the duration of the contraction is only slightly increased. Its use as an antiarrhythmic drug, then, comes from its direct and indirect parasympathetic stimulating properties. Vagus nerve stimulation slows down conduction at the AV node by increasing the refractory period of cardiac myocytes. The slowed AV node gives the ventricles more time to fill before contracting.
Mitapivat, sold under the brand name Pyrukynd, is a medication used to treat hemolytic anemia. It is taken as the sulfate hydrate salt by mouth. Mitapivat is a pyruvate kinase activator.Mitapivat was approved for medical use in the United States in February 2022. Medical uses
Mitapivat is indicated for the treatment of hemolytic anemia in adults with pyruvate kinase deficiency. Pharmacology
Mechanism of action
Mitapivat binds to and activates pyruvate kinase, thereby enhancing glycolytic pathway activity, improving adenosine triphosphate (ATP) levels and reducing 2,3-diphosphoglycerate (2,3-DPG) levels. Mutations in pyruvate kinase cause deficiency in pyruvate kinase which prevents adequate red blood cell (RBC) glycolysis, leading to a buildup of the upstream glycolytic intermediate 2,3-DPG and deficiency in the pyruvate kinase product ATP. Society and culture
Legal status
On 15 September 2022, the Committee for Medicinal Products for Human Use (CHMP) of the European Medicines Agency (EMA) adopted a positive opinion, recommending the granting of a marketing authorization for the medicinal product Pyrukynd, intended for the treatment of an inherited condition called pyruvate kinase deficiency. The applicant for this medicinal product is Agios Netherlands B.V.

Names
Mitapivat is the international nonproprietary name (INN). References
Further reading
Kung C, Hixon J, Kosinski PA, Cianchetta G, Histen G, Chen Y,  et al. (September 2017). "AG-348 enhances pyruvate kinase activity in red blood cells from patients with pyruvate kinase deficiency". Blood. 130 (11): 1347–1356. doi:10.1182/blood-2016-11-753525. PMC 5609468. PMID 28760888. Rab MA, Van Oirschot BA, Kosinski PA, Hixon J, Johnson K, Chubukov V,  et al. (January 2021).