Anti-arrhythmic Drugs

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Digoxin is originated from the foxglove plant. It is usually given to patients who suffer from arrhythmias. Arrhythmia is a condition in which the myocardium beings to either beat too fast (tachycardia) or beat too slow (bradycardia). Antiarrhythmic drugs are given to the patient to correct these non-synchronous contractions and bring the myocardium back into a normal rhythm. Pharmacodynamics Digoxin is a cardiac glycoside; its pharmacological properties are related to its ability to inhibit the sodium-potassium ATPase. Digoxin upon administration causes the intracellular levels of sodium to increase, above normal physiological concentrations. This increase in sodium levels causes the sodium-calcium exchanger to be active. This then exchanges the intracellular sodium for extracellular calcium. This extracellular calcium upon entry into the myocardium induces intracellular calcium to be released due to calcium induced calcium release (CIRC). Digoxin has a negative chronotropic and positive inotropic effect on the myocardium; these can be explained by the electro-physiochemical changes which take place across the myocardium upon the application of digoxin. The negative chronotropy is due to the sodium-potassium ATPase being inhibited, this then leads to a less number of action potentials (APs) being generated and as a result if less APs are being generated this will have a negative effect on the rate at which the myocardium contracts (negative chronotropic effect). The positive inotropic effects are linked with the activation of the sodium-calcium exchanger, upon activation it introduces extracellular calcium into the myocardium, this extracellular calcium along with the intracellular calcium (CIRC) causes an increase in the forc... ... middle of paper ... ...). Stockley's Drug Interactions - Digoxin. [ONLINE] Available at: [Accessed 2 February 2012]. The Digitalis Investigation Group, (1997). The Effect of Digoxin on Mortality and Morbidity in Patients with Heart Failure. New England Journal Medicine, (issue 336). pp 525-533 The electronic Medicines Compendium (eMC), (2011). Capoten Tablets - Patient Information Leaflet (PIL). [ONLINE] Available at: [Accessed 15 February 2012]. The electronic Medicines Compendium (eMC), (2012). Digoxin Tablets BP 250 micrograms - Summary of Product Characteristics (SPC). [ONLINE] Available at: [Accessed 2 February 2012].

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