Digitalis glycosides Digoxin

Fig. 1 Fluorescence scan of a mixture of digitalis glycosides. Digoxin (DG3), digoxigenin bis-digitoxoside (DGj), digoxigenin mono-digitoxoside (DGi), digoxigenin (DG).

Digitalis glycosides (digoxin) Digitalis glycosides (digoxin) cause a decrease in maximal diastolic potential and action potential duration and increase the slope of phase 4 depolarization. 

Drugs that may affect spironolactone include ACE inhibitors, salicylates, and food. Drugs that may be affected by spironolactone include anticoagulants, digitalis glycosides, mitotane, digoxin, and potassium preparations. 

Digoxin is indicated in patients with heart failure and atrial fibrillation. It is also most helpful in patients with a dilated heart and third heart sound. It is usually given only when diuretics and ACE inhibitors have failed to control symptoms. Only about 50% of patients with normal sinus rhythm (usually those with documented systolic dysfunction) will have relief of heart failure from digitalis. Better results are obtained in patients with atrial fibrillation. If the decision is made to use a cardiac glycoside, digoxin is the one chosen in most cases (and the only one available in the USA). When symptoms are mild, slow loading (digitalization) with 0.125-0.25 mg per day is safer and just as effective as the rapid method (0.5-0.75 mg every 8 hours for three doses, followed by 0.125-0.25 mg per day). 

Absorption of certain drugs, including those with neutral or cationic charge as well as anions, may be impaired by the resins. These include digitalis glycosides, thiazides, warfarin, tetracycline, thyroxine, iron salts, pravastatin, fluvastatin, folic acid, phenylbutazone, aspirin, and ascorbic acid. Any additional medication (except niacin) should be given 1 hour before or at least 2 hours after the resin to ensure adequate absorption. Colesevelam does not bind digoxin, warfarin, or reductase inhibitors. 

Digitalis glycosides [NE] Decreased gastrointestinal absorption of digitoxin (possibly also digoxin). 

Pedersen KE. Digoxin interactions. The influence of quinidine and verapamil on the pharmacokinetics and receptor binding of digitalis glycosides. Acta Med Scand Suppl 1985 697 1-40. 

Examples of specific drugs used in the treatment of chronic heart failure include digitalis glycosides (e.g., digoxin, positive inotropic agent), diuretics (hydrochlortiazide and furosemide), and vasodilators (nitrates such as nitroglycerin, ACE inhibitors, such as captopril, and hydralazine). 

Drugs interacting with digoxin and other digitalis glycosides. 

Digitalis glycosides augment contractile force and are likewise used in severe forms of insuf ciency, specifically in the presence of concomitant atrial fibrillation. Because of the narrow margin of safety, the digoxin dose must be adjusted individually in each patient. 

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