Pharm 1 Final Exam Study Guide 1. Digoxin- Book Information- Diuretics are the first-line drug treatment for reducing fluid volume. They are frequently prescribed with digoxin or other agents. Aloe may increase the risk of digitalis toxicity. It increases potassium loss, which increases the effect of digoxin. Ginseng may falsely elevate digoxin levels. • St. John's wort decreases absorption of digoxin and thus decreases serum digoxin level. • Psyllium (Metamucil) may decrease digoxin absorption. • Hawthorn may increase the effect of digoxin. • Licorice can potentiate the effect of digoxin. It promotes potassium loss (hypokalemia), which increases the effect of digoxin. It may cause digitalis toxicity. Pharmacokinetics The absorption rate of digoxin in oral tablet form is 70%. The rate is 90% in liquid and capsule form. The protein-binding power for digoxin is 30%. The half-life is 30 to 40 hours. Because of its long half-life, drug accumulation can occur. Side effects should be closely monitored to detect digitalis toxicity. Patients should be made aware of side effects that need to be reported to the health care provider. Serum digoxin levels are most commonly drawn when actual digitoxicity is suspected. This allows the health care provider to ascertain the extent of such toxicity and to confirm elimination of the drug after it is stopped or decreased in dosage (see the Digitalis [Digoxin] Toxicity section later in this chapter). Thirty percent of digoxin is metabolized by the liver, and 50% to 70% is excreted by the kidneys mostly unchanged. Kidney dysfunction can affect the excretion of digoxin. Thyroid dysfunction can alter the metabolism of cardiac glycosides. For patients with hypothyroidism, the dose of digoxin should be decreased; in hyperthyroidism, the dose may need to be increased. Pharmacodynamics In patients with a failing heart, cardiac glycosides increase myocardial contraction, which increases cardiac output and improves circulation and tissue perfusion. Because these drugs decrease conduction through the AV node, the heart rate decreases. The onset and peak actions of oral and intravenous (IV) digoxin vary. The therapeutic serum level is 0.8 to 2.0 ng/mL for digoxin. To treat HF, the lower serum therapeutic levels should be obtained, and for atrial fibrillation, the higher therapeutic serum levels are required. Digoxin can be administered orally or IV. Table 42-2 lists the digitalis preparations and their dosages, uses, and considerations. Digitalis (Digoxin) Toxicity
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- Fall '16
- Christy McCall
- digoxin, mannitol, serum digoxin level, serum digoxin , Nsg6005 Discussion Question