Cardiac glycosides adverse effects

Dlgltoxin. Digitoxin is a cardiac glycoside obtained from Digitalis purpurea. Digitoxin is indicated in the treatment of atrial flutter, atrial fibrillation, and supraventricular tachycardia. Its electrophysiologic and adverse effects are similar to those described for digoxin (87). 

Cardiac glycosides have a small ratio of toxic to therapeutic concentration. Possible adverse effects are nausea, vomiting, abdominal pain, diarrhoea, fatigue, headache, drowsiness, colour vision disturbances, sinus bradycardia, premature ventricular complexes, AV-block, bigeminy, atrial tachycardia with AV-Block, ventricular fibrillation. There are several mechanisms relevant for their toxic action (Table 2). 

The side-effects of cardiac glycosides are mostly caused by electrophysiological/neuronal phenomena. Gastro-intestinal adverse reactions are probably triggered by effects on the central nervous system. Various types of cardiac arrhythmias are caused by the influence of the drugs on nodal tissues in the heart. The risk of arrhythmia is strongly enhanced by low plasma potassium concentrations. 

Adverse effects Thiazide diuretics induce hypokalemia and hyperuricemia in 70% of patients, and hyperglycemia in 10% of patients. Serum potassium levels should be monitored closely in patients who are predisposed to cardiac arrhythmias (particularly individuals with left ventricular hypertrophy, ischemic heart disease, or chronic congestive heart failure) and who are concurrently being treated with both thiazide diuretics and digitalis glycosides (see p. 160). Diuretics should be avoided in the treatment of hypertensive diabetics or patients with hyperlipidemia. 

GRAPEFRUIT JUICE CARDIAC GLYCOSIDES-DIGOXIN Possible T efficacy and T adverse effects Possibly via altered absorption Most patients were unaffected. Consider if unexpected bradycardia or heart block with digoxin. Rationale is based on the theoretical concept that digoxin is a substrate of P-gp... 

In a randomized study in 401 patients who had taken an overdose of oleander seeds, which contain cardiac glycosides, activated charcoal 50 g every 6 hours for 3 days was compared with sterile water. There were fewer deaths in the treatment group, 2.5% versus 8% (1). There were no important adverse effects. 

Xysmalobium undulatum (xysmalobinm) contains the cardiac glycoside ascleposide. It has been nsed topically to treat wonnds (2). Its adverse effects are likely to be those of other cardiac glycosides (see monograph on Cardiac glycosides). 

Many aspects of the pharmacology, clinical pharmacology, and adverse effects and interactions of cardiac glycosides have been reviewed (1-12). 

The adverse effects of cardiac glycosides can be cardiac or non-cardiac. They mostly occur through toxicity and are time-independent (DoTS classification) susceptibility factors include electrolj4e abnormalities (particularly hypokalemia), renal insufficiency, and age. 

Frequent cardiac adverse effects include heart block and ectopic dysrhythmias (ventricular extra beats, other ventricular tachydysrhythmias, and paroxysmal supraventricular tachycardia). The combination of heart block with an ectopic dysrhythmia, for example paroxysmal supraventricular tachycardia with block, is particularly suggestive of toxicity due to cardiac glycosides. Any other dysrhythmia can occasionally be caused by cardiac glycosides. 

Long-term use and cardiovascular adverse effects of cardiac glycosides... 

A number of important characteristics exist that distinguish drug therapy in infants from adult medication protocols. For example, after intramuscular administration, drug absorption is partially dependent on blood flow in the muscle bed. Abnormal drug absorption following intramuscular injection can occur in premature infants, in whom muscle mass is small and blood flow to the musculature is poor. Examples of adverse effects attributed to altered drug absorption are the reactions of infants to cardiac glycosides and anticonvulsants. 

Adverse effects of diuretics are excessive potassium and hydrogen ion loss leading to hypokalaemia and metabolic alkalosis. Hypokalaemia enhances the toxic effects of cardiac glycosides. 

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