Question

Drug card for

2. Cardiotonics

digoxin (Lanoxin)

Answer 1

Cardiotonic drugs are drugs, which increase cardiac contractile force during heart failure.
Heart failure (HF) is a pathological state during which cardiac output is inadequate to provide the
minute volume needed by the body or relatively normal minute volume and blood supply of the
peripheral tissues is provided by the congested load of the heart.

Classification of cardiotonic drugs:

1.Cardiac glycosides /CGs/– Strophantine, Digoxin, Corglycon

2.Sympathomimetic drugs

• β - adrenomimetics –Prenalterol, Xamoterol
• Catecholamines and their derivatives – Dopamine, Dobutamine

3. Phosphodiesterase inhibitors

• Bipyridine derivatives – Amrinone, Milrinone
• Imidazole derivatives – Enoximone, Piroximone, Fenoximone
• Benzimidazole derivatives - Pimobendane

4. Cardiotonic drugs with other mechanism - Vesnarinone, Forskoline.

DIGOXIN (Generic) LANOXICAPS / LANOXIN (Trade) CLASSIFICATION: Cardiac Glycosides

USES: Heart Failure; Atrial fibrillation and atrial flutter; Paroxysmal atrial tachycardia

ACTION: increases force of Myocardial contractions; prolongs refractory period of the AV node; Decreases conduction through the SA and AV nodes.

THERAPEUTIC EFFECT: Increase cardiac output (positive inotropic effect) and slowing of the heart rate (negative chronotropic effect)

DOSAGE FOR ADULTS: IV: Initial Loading/Digitalizing dose: 0.5-1 mg given as 50% of the dose initially and one quarter of the initial dose in each of the 2 subsequent doses at 6-12h intervals PO: Initial Loading/Digitalizing dose: 0.75-1.5mg given as 50% of the dose initially and one quarter of the initial dose in each of 2 subsequent doses at 6-12h intervals. For geriatric patients, initial dose should not exceed 0.125mg. Maintenance Dose: 0.125-0.5mg/day as tablets or 0.35-0.5mg/day asgelatin capsules.

PHARMACOKINETICS: Absorption: PO: 60-80% absorbed from tablets; 70-85% absorbed from elixir; 90-100% absorbed from liquid-filled capsules Distribution: Widely distributed Metabolism and Excretion: Excreted almost entirely unchanged by the kidneys Half-Life: 36-48h; increased with renal impairment ROUTE ONSET PEAK DURATION (with normal renal function) PO 30-120 minutes 2-8 hours 2-4 days IM 30 minutes 4-6 hours 2-4 days IV 5-30 minutes 1-4 hours 2-4 days

CONTRAINDICATIONS: Hypersensitivity; Uncontrolled ventricular arrhythmias; AV block (without pacemaker); Idiopathic hypertrophic subaorticstenosis; Constrictive pericarditis; Known alcohol intolerance (for Digoxin elixir only) USE WITH CAUTION: Hypokalemia (increase risk of digoxin toxicity); Hypercalcemia (increase risk of digoxin toxicity); with diuretics; Hypothyroidism; Geriatric Patients; Myocardial Infarction; Renal Impairment; Obesity

ADVERSE EFFECTS: Most Common: Tachycardia, headache, dizziness, mental disturbance, nausea and vomitting, diarrhea, anorexia, blurred or yellow vision CNS: Fatigue, weakness CV: Arrhythmias, bradycardia, ECG Changes, AV Block, SA Block GI: Anorexia, diarrhea Hemat: Thrombocytopenia Metabolic: Electrolyte imbalances with acute digoxin toxicity

DRUG INTERACTIONS: Thiazide and Loop Diuretics, piperacillin, ticarcillin, amphotericin B, corticosteroids, and excessive use of laxatives may cause hypokalemia and increase the risk of Digoxin toxicity. Amiodarone, some benzodiazepines, cyclosporine, diphenoxylate, indomethacin, itraconazole, propafenone, quinidine, quinine, spironolactone, and verapamil may increase levels and lead to toxicity. Levels may be decreased by some antineoplaxtics, activated charcoal, cholestyramine, colestipol, kaolin/pectin, metoclopramide, penicillamine, rifampin, or sulfasalazine. Additive bradycardia may occur with beta-blockers, diltiazem, verapamil, clonidine, and other antiarrhythmics. Use with sympathomimetics may increase risk of arrhythmias Thyroid hormones may decrease therapeutic effects

NURSING CONSIDERATIONS: Measure liquid precisely. Obtain written parameters for when medication is held. Changes in rate or rhythm may indicate toxicity. Expect reduction indosage if changing from PO form to parenteral form. Give IV injections over 5 minutes or longer ASSESSMENT: Before: Monitor Apical Pulse for 1 minute; if <60bpm, hold dose and notify physician. Also notify of any significant changes in rate, rhythm, or qualityof pulse. Before loading dose administration, determine whether patient has taking any digitalis preparations in the last 2-3 weeks. During: Monitor BP periodically for IV. Monitor ECG throughout IV and 6h after each dose. Notify physician if bradycardia or new arrhythmias occur. Monitor intake and output ratios and daily weights. Assess for peripheral edema and crackles on lung auscultation. After: Digoxin is associated with increased risk for falls in elderly. Evaluate serum electrolyte levels (especially potassium, magnesium, and calcium). Evaluate renal and hepatic function for digoxin toxicity. For geriatric patients, levels may be in normal range but toxicity may still occur, assess for symptoms of toxicity: abdominal pain, anorexia, nausea, vomiting, visual disturbances, bradycardia, and other arrhythmias. Monitor therapeutic serum digoxin levels range 0.5-2 ng/mL. Monitor Vital signs and Complete Blood Count. PATIENT TEACHING: Take medication as directed at the same time each day. Do not take with grapefruit juice. Take any missed doses 12h of the scheduled dose or omit it. Do not take double doses. Consult health care professional if doses are missed for 2 or more days. Do not discontinuing without consultation. Teach patient to take pulse and contact health care professional before taking medication if pulse is <60bpm or >100bpm. For geriatric patients review all fall prevention strategies with patient, family, and care takers. Stress importance of routine examinations to determine drug effectiveness and monitor for toxicity.