Toxicity digitalis

Phenytoin. Phenytoin sodium is sodium diphenylhydantoin [630-93-3] which is stmcturally related to the barbiturates. It was originally introduced as an anticonvulsant (18) (see Hypnotics, sedatives, and anticonvulsants) and later found to have antiarrhythmic properties (19), although not approved by the PDA for any arrhythmic indications. Phenytoin is effective in the treatment of ventricular arrhythmias associated with acute MI and with digitalis toxicity (20). It is not very effective in treatment of supraventricular arrhythmias (20). 

Buspirone causes less additive CNS depression than do the other antianxiety drugs. However, it is recommended that concurrent use with a CNS depressant be avoided. Buspirone may increase serum digoxin levels, which increases the risk of digitalis toxicity. 

The cardiotonics are contraindicated in patients with known hypersensitivity, ventricular failure, ventricular tachycardia, or AV block and in the presence of digitalis toxicity. 

The drug should also be withheld and the physician contacted if there are any signs of digitalis toxicity, there is any change in the pulse rhythm, there is a marked increase or decrease in the pulse rate since the last time it was taken, or the patient s general condition appears to have worsened. 

Digitalis toxicity can occur even when normal doses are being administered or when the patient has been receiving a maintenance dose Many symptoms of toxicity are similar to tiie symptoms of the heart conditions for which tiie patient is receiving the cardiotonic. This makes careful assessment of the patient by the nurse a critical aspect of care... 

Older adults are particularly prone to digitalis toxicity. Ail older adults must be carefully monitored for signs of digitalis toxicity. 

The nurse must also closely observe die patient for odier adverse drug reactions, such as anorexia, nausea, vomiting, and diarrhea. Some adverse drug reactions are also signs of digitalis toxicity, which can be serious. The nurse should carefully consider any patient complaint or comment, record it on die patient s chart, and bring it to die attention of the primary care provider. 

Hypokalemia makes the heart muscle more senstive to digitalis thereby increas ng thepossbility of developing digitalis toxicity. The nurse must closely, and at frequent intervals observe patients with hypokalemia forsgnsofdigitalistoxicity. 

Fhtients with hypomagnesemia (low magnesium plasma levels) are at increased risk for digitalis toxicity. If low magnesium levels are detected, die primary care provider may prescribe magnesium replacement dierapy. 

All antiarrhythmic dra are used cautiously in patients with renal or hepatic disease. When renal or hepatic dysfunction is present, a dosage reduction may be necessary. All patients should be observed for renal and hepatic dysfunction. Quinidine and procainamide are used cautiously in patients with CHF. Disopyramide is used cautiously in patients with CHF, myasthenia gravis, or glaucoma, and in men with prostate enlargement. Bretylium is used cautiously in patients with digitalis toxicity because the initial release of norepinephrine with digitalis toxicity may exacerbate arrhythmias and symptoms of toxicity. Verapamil is used cautiously in patients with a history of serious ventricular arrhythmias or CHF. Electrolyte disturbances such as hypokalemia, hyperkalemia, or hypomagnesemia may alter the effects of the antiarrhythmic dru . Electrolytes are monitored frequently and imbalances corrected as soon as possible... 

When two antiarrhythmic dragp are administered concurrently the patient may experience additive effects and is at increased risk for drug toxicity. When quinidine and procainamide are administered with digitalis, tiie risk of digitalis toxicity is increased. Hiarmacologic effects of procainamide may be increased when procainamide is administered with quinidine When quinidine is administered with the barbiturates or cimetidine, quinidine serum levels may be increased. When quinidine is administered with verapamil, there is an increased risk of hypotensive effects. When quinidine is administered with disopyramide, there is an increased risk of increased disopyramide blood levels and/or decreased serum quinidine levels. 

Co-administration may enhance the possibility of digitalis toxicity associated with hypokalemia. 

Calcium is contraindicated in patients with hypercalcemia or ventricular fibrillation and in patients taking digitalis. Calcium is used cautiously in patients with cardiac disease. Hypercalcemia may occur when calcium is administered with the thiazide diuretics. When calcium is administered with atenolol there is a decrease in Hie effect of atenolol, possibly resulting in decreased beta blockade. There is an increased risk of digitalis toxicity when digitalis preparations are administered with calcium. The clinical effect of verapamil may be decreased when the drug is administered with calcium. Concurrent ingestion of spinach or cereal may decrease file absorption of calcium supplements. 

Avoid if suspected digitalis toxicity. If severe symptomatic hyperkalemia and concomitant digoxin toxicity, treat with Digibind prior to infusing calcium if time permits... 

Ventricular tachycardia (VT) is defined by three or more repetitive PVCs occurring at a rate greater than 100 beats/min. It occurs most commonly in acute myocardial infarction (MI) other causes are severe electrolyte abnormalities (e.g., hypokalemia), hypoxemia, and digitalis toxicity. The chronic recurrent form is almost always associated with underlying organic heart disease (e.g., idiopathic dilated cardiomyopathy or remote MI with left ventricular [LV] aneurysm). 

If severe symptoms are present, synchronized DCC should be instituted immediately to restore sinus rhythm. Precipitating factors should be corrected if possible. If VT is an isolated electrical event associated with a transient initiating factor (e.g., acute myocardial ischemia, digitalis toxicity), there is no need for long-term antiarrhythmic therapy after precipitating factors are corrected. 

Hypercalcemia from any cause predisposes the patient to digitalis toxicity. Calcium, particularly when administered rapidly by the IV route, may produce serious arrhythmias in digitalized patients. On the other hand, hypocalcemia can nullify the effects of digoxin in humans thus, digoxin may be ineffective until serum calcium is restored to normal. 

Electrical cardioversion It may be desirable to reduce the dose of digoxin for 1 to 2 days prior to electrical cardioversion of atrial fibrillation to avoid the induction of ventricular arrhythmias, but physicians must consider the consequences of increasing the ventricular response if digoxin is withdrawn. If digitalis toxicity is suspected, delay elective cardioversion. If it is not prudent to delay cardioversion, select the lowest possible energy level to avoid provoking ventricular arrhythmias. Lab test abnormalities Periodically assess serum electrolytes and renal function (serum creatinine concentrations) the frequency of assessments will depend on the clinical setting. 

Cardiac effects Use with caution and in lower doses in patients with CHF, reduced cardiac output, digitalis toxicity accompanied by AV block and in the elderly. 

Aerosol - Events associated with aerosolized ribavirin have included cardiac arrest, hypotension, bradycardia, and digitalis toxicity. Bigeminy, bradycardia, and tachycardia have been described in patients with underlying congenital heart disease. 

Aerosol Adverse reactions may include anemia and hemolytic anemia apnea atelectasis bacterial pneumonia bigeminy bradycardia bronchospasm cardiac arrest conjunctivitis cyanosis digitalis toxicity dyspnea hypotension hypoventilation pneumothorax pulmonary edema rash reticulocytosis tachycardia ventilator dependence worsening of respiratory status. 

The current hypothesis regarding the cellular basis for the positive inotropic effect of digitalis helps to explain some of the wide individual variability in the dosage required to develop digitalis toxicity. Differences in pH, ischemia, Na+, K+, and Ca++ can each alter the likelihood of developing toxicity within the same patient and between individuals. 

Quinidine can increase the plasma concentrations of digoxin, which may in turn lead to signs and symptoms of digitalis toxicity. Gastrointestinal, central nervous system (CNS), or cardiac toxicity associated with elevated digoxin concentrations may occur. Quinidine and digoxin can be administered concurrently however, a downward adjustment in the digoxin dose may be required. 

Phenytoin, like lidocaine, is more effective in the treatment of ventricular than supraventricular arrhythmias. It is particularly effective in treating ventricular arrhythmias associated with digitalis toxicity, acute myocardial infarction, open-heart surgery, anesthesia, cardiac catheterization, cardioversion, and angiographic studies. 

Most effective against arrhythmias associated with digitalis toxicity and exercise, particularly if the latter is related to ischemia. 

Rule out digitalis toxicity if nausea, vomiting, arrhythmias develop... 

Hyperkalemia may occur as a result of digitalis toxicity. Signs and symptoms of hyperkalemia include diarrhea, paresthesia of extremities, heaviness of legs, decreased BP, cold skin, grayish pallor, hypotension, mental confusion, irritability, flaccid paralysis, tented T waves, widening QRS interval, and ST depression. 

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