Digitalis glycosides toxicity

Lldoc ine. Lidocaine hydrochloride, an anilide, was originally introduced as a local anesthetic in 1943 and found to be a potent antiarrhythmic in 1960. The compound is a reverse amide of procainamide. Lidocaine is generally considered to be the dmg of choice in the treatment of ventricular arrhythmias and those originating from digitalis glycoside toxicity (1,2,15—17). 

Fhtients taking a diuretic and a digitalis glycoside must be monitored closely. Thiazide and loop diuretics (see Chap. 46) may increase the risk and effects of toxicity. 

Marsh JD, Smith TW. Epidemiology and general considerations of digitalis toxicity. In Smith TW, ed. Digitalis glycosides. Orlando, Fla Grune and Stratton, 1986 217-225. 

As with the digitalis glycosides, the toxic effects of the anticonvulsant drug diphenylhydantoin result from elevated plasma levels of the drug. This can simply be due to inappropriate dosage, but other factors may also be involved in the development of toxicity. 

The most common cardiac manifestations of glycoside toxicity include atrioventricular junctional rhythm, premature ventricular depolarizations, bigeminal rhythm, and second-degree atrioventricular blockade. However, it is claimed that digitalis can cause virtually every variety of arrhythmia. 

The site responsible for the pharmacological and toxic actions of digitalis glycosides is associated with which of the following ... 

The prevalence of digitalis intoxication is from 16% to 20%. Color vision disturbances are especially common and may occur before, simultaneously with, or after the onset of cardiac toxicity. Although color vision disturbances are associated with cardiac glycoside toxicity decreased visual acuity without the accompanying classic symptom of xanthopsia is also common. 

Smith TW, Antman EM, Friedman PL, Blatt CM, Marsh JD. Digitalis glycosides mechanisms and manifestations of toxicity. Prog Cardiovasc Dis 1984 26(6) 495-540 1984 27(l) 21-56. 

Digitalis glycosides + docusate sodium (DOSS) Increased absorption of digitalis to a possibly toxic level Surface-active properties of DOSS increases wetting and perhaps solubility and absorption of poorly absorbed digitalis Space doses by 2-3 h... 

Chronic toxicity develops following the use of herbal products or teas that contain foxglove. The development of toxicity is unpredictable since the digitalis glycoside content of these products is not standardized. This is now extremely rare. 

Alteration of the movement of ions, such as potassium, in heart tissue may be a toxic response to some foreign compounds. For example, the digitalis glycosides cause changes in tissue potassium and this may lead to serious cardiac effects. Diuretics may also cause low plasma potassium with potentially dangerous effects on heart function. 

Digitalis glycosides cause an influx of extracellular calcium and an accumulation of extracellular potassium. The increased levels of extracellular potassium decrease the rate of repolarization of the cardiac cell. Thus, as levels of the drug approach the toxic range, accumulated extracellular potassium causes a lengthening of phase 3 of the cardiac action potential and an increase in the length of time between depolarizations. Thus, bradycardia is seen. 

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