Digoxin

Description overdue on 07.02.2012

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Cardiac glycosides.   Herbal drug digoxin was prepared from woolly foxglove   (Digitalis). It possesses strong cardiotonic action   (positive inotropic effect, increase cardiac contractility by increasing the calcium ion concentration in cardiomyocytes), thereby increasing the stroke volume and cardiac output. It reduces the need for oxygen in myocardial cells. It also has a negative dromotropic and negative chronotropic effect, ie reduces the frequency of oscillation of the electric pulse sinus node and conduction velocity of the atrioventricular conduction system of the heart. Also it has an indirect effect on the receptors of the aortic arch and increases the activity of the vagus nerve that slows the activity sinoatrial node . These mechanisms can achieve reduction in heart rate during supraventricular (supraventricular) tachyarrhythmia (paroxysmal or persistent form of atrial tachyarrhythmias, atrial flutter).

In severe disease of the heart and signs of stagnation for large and small circles of blood circulation Digoxin has indirect   vasodilatory action That manifests itself in the decrease of the total resistance of peripheral vascular bed and reduction of severity of dyspnea and peripheral edema .  Taken orally, it is absorbed in the digestive tract of 70% of active ingredient after administration Digoxin limiting concentration is reached in the range of from two to 6 hours .  Parallel ingestion leads to some increase in suction time .  Exceptions are foods rich in plant fiber - in this case, part of the active substance is absorbed fiber and becomes available .  Tends to accumulate in body fluids and tissues, including the myocardium, which is used to determine patterns of use: the drug effect was calculated by the maximum not in the plasma concentration of the substance, and the content at equilibrium state pharmacokinetics .  50-70% of the drug is excreted by the kidneys, severe pathology of the body may contribute to the accumulation in the body Digoxin .  The half-life up to two days .

Indications:

Digoxin is indicated for heart rhythm disturbances (arrhythmias) supraventricular character (paroxysmal atrial tachyarrhythmia,   auricular flutter Constant atrial tachyarrhythmia ). Digoxin is included in the scheme of treatment of chronic heart failure, the third and fourth functional class, and is also used in the second class of CHF if diagnosed by clinical manifestations.

Contraindications:

Direct contraindications for digoxin are signs of glycoside intoxication, hypersensitivity to digoxin, Wolff-Parkinson-White , Atrioventricular block second degree and complete atrioventricular block, bradycardia . Digoxin should not be prescribed in such manifestations of coronary heart disease as the unstable angina   and the acute phase of myocardial infarction. Contraindicated drug in isolated mitral stenosis . Diastolic heart failure type (for cardiac tamponade At constrictive pericarditis At amyloidosis of the heart When cardiomyopathy) is also a contraindication to digoxin. Marked dilatation of the heart, obesity , Renal failure, and hepatic parenchyma, inflammation infarction, hypertrophy of the interventricular septum, subaortic stenosis , Ventricular tachyarrhythmias - in these conditions the use of Digoxin is unacceptable.

Side effect:

The first thing to pay attention to the possible side effects of the cardiovascular system, as they can be the first signs of a developing glycoside intoxication . These symptoms include slowing atrioventricular conduction and, consequently, slower rhythm (bradycardia), the occurrence of heterotrophic centers of excitation of the myocardium, which manifests itself in the development of ventricular arrhythmias ( arrythmia ) And ventricular fibrillation . Extracardiac side effects are not present, unlike the intracardiac, life-threatening. These are signs of dysfunction of the digestive tract (nausea, stomach pain, vomiting and diarrhea), nervous system (headache, depression or psychosis, a disruption of the visual analyzer in the form of flies in front of the eyes, etc.). From the blood may be a violation of a morphological picture thrombocytopenia And it will appear petechiae in the skin. Possible development of allergic reactions in the form of Digoxin erythema skin , Itching and rash.

Mode of application:

Inclusion of digoxin in the scheme of treatment should be done only in a hospital. The therapeutic window of digoxin (the interval between therapeutic and toxic dose) is extremely small, and therefore, all of the recommendations for receiving the drug should be observed strictly. In the first stage of treatment (step digitalization or saturation of the patient preparation) Digoxin administered at a dosage which is called saturation: the patient receives from two to four tablet (equivalent to 500 micrograms - one milligram), and then move on to receive one tablet with every 6 hours. This continues until receipt of the therapeutic effect and stable digoxin concentration in the blood is within seven days.

The next step is moving to a regular intake of a maintenance dose of the drug, which is generally poltabletki or one tablet per day (one tablet contains 250 micrograms Digoxin active substance). You can not miss taking the drug, as well as impossible at one time to take twice the dose when skipping dosage. It is fraught with the development of intoxication, which can result in fatal.   The Department of Cardiology and CCU Digoxin and intravenously administered with a view to the relief of supraventricular paroxysmal tachyarrhythmias .

Special instructions:

The effect of digoxin on the fetus in clinical trials has not been studied, but the drug is able to overcome blood-placenta barrier   and into the body of the fetus. Digoxin is prescribed during pregnancy only in emergency indications. If a nursing mother is taking digoxin, the child should be continuously monitored heart rate. In pediatric tablet form Digoxin is not used. Overdose symptoms (glycoside intoxication): slows down the heart rate, it appears sinus bradycardia . An electrocardiogram shows signs of slow atrioventricular conduction, up to complete atrioventricular block. Heterotrophic sources give PVCs rhythm, ventricular fibrillation is possible. Extracardiac symptoms of intoxication glycosides appear dyspepsia (nausea, diarrhea, anorexia), memory loss, and cognitive functions , Drowsiness, pain in the head, weakness in muscles, erectile dysfunction , Gynecomastia, psychosis, anxiety, euphoria , Xanthopsia, decreased visual acuity and other violations in the work of the visual analyzer.

If signs of intoxication glycosides strategy depends on the severity of symptoms: it is enough to reduce the dose of Digoxin with minor manifestations of overdose. If there is a progression of side effects, it is necessary to make a short break, the duration of which depends on the dynamics of the signs of intoxication. Acute digoxin requires gastric lavage, reception of sorbents in large quantities. The patient gives a laxative.

Ventricular fibrillation can be eliminated by intravenous administration of potassium chloride with the addition of insulin . Potassium supplements, you should not appoint slowing atrioventricular conduction. When you save the arrhythmia is administered intravenously phenytoin . For the treatment of bradycardia, atropine is used. Parallel to prescribe oxygen therapy   and drugs that increase blood volume. Digoxin is the antidote Unitiol .

Drug Interactions:

Digoxin may not be combined with alkali, acid, heavy metal salts and tannin. When used in conjunction with diuretics, insulin, calcium preparations, sympathomimetics glucocorticosteroids   increased risk of symptoms of glycoside intoxication.

In combination with quinidine, amiodarone   and erythromycin   there is an increase in the blood content of Digoxin. Quinidine inhibits the excretion of digoxin. Calcium-channel blocker verapamil   Digoxin reduces the rate of elimination from the kidneys, which leads to increased concentrations of the cardiac glycoside. This action of verapamil is gradually leveled by prolonged joint reception drugs (more than six weeks).

Combination with amphotericin B   increases the risk of overdose due to glycosides hypokalemia Which provokes amphotericin B. hypercalcemia increases the susceptibility of cardiomyocytes for cardiac glycosides, and therefore should not resort to intravenous calcium supplementation in patients who are taking cardiac glycosides. Simultaneous administration of digoxin in combination with reserpine . propranolol , Phenytoin increases the risk of ventricular arrhythmias.

Reduces the concentration and efficacy of Digoxin phenylbutazone   and preparations of barbiturates. Also, reduce the therapeutic effect of potassium supplements, drugs, reducing the acidity of gastric juice, metoclopramide . Digoxin When combined with antibiotics erythromycin and gentamicin   glycoside content increases in the patient's plasma. Simultaneous administration of Digoxin with colestipol, cholestyramine   and laxative magnesium leads to deterioration of absorption of the drug in the intestine, which means a reduction in the number and digoxin in the body. Metabolism glycosides accelerated by the combined reception with rifampicin and sulfosalazinom.