Cardiac drugs Cardiac glycoside Cardiac glycosides are the most effective drugs for treatment of C.H.F. Digitoxins are plant alkaloids. They increase myocardial contractions, which will increase blood supply to all organs including the kidneys therefore causing diuresis, which will decrease the edema. They are used to treat cardiac arrhythmia because they decrease heart rate.

Action: They increase the force of myocardial contractions (positive inotropic). It increases the contractility of the heart muscle by minimizing the movement of Na + and K + ions and increasing the release of Ca ++ ions in the myocardial cells. It decreases the heart rate due to increase in parasympathetic nervous system and decrease in the sympathetic tone. They are primarily excreted through the kidneys. The initial dose is the larger dose (the loading or digitalizing dose), the subsequent doses are referred to as (Maintenance doses).

Results: Decrease in venous pressure. Coronary dilatation. Reduce heart size. Marked diuresis and decreasing edema.

Indications: Congestive heart failure (C.H.F). Cardiac arrhythmia (atrial fibrillation, atrial flutter and sinus tachycardia). Contraindication: Hypersensitivity. Angina pectoris in absence of CHF. Given with caution for elderly and people who have kidney failure.

Side effects 1. They are extremely toxic and may cause death. 2. There is a narrow margin of safety between the therapeutic dose and the toxic dose. 3. Could cause overdose by cumulative effects of the drug, so frequent assessment of the serum level is essential. 4. May cause cardiac arrhythmia such as bradycardia (below than 60 beat/ minute), ventricular fibrillation (which may lead to cardiac arrest and death), and Bigeminal rhythm. 5. Nausea, vomiting, and diarrhea. 6. Headache, malaise and muscle weakness. 7. Skin rashes, blurring of vision, diplopia and white halos.

Note:  Patients suffering from digitalis intoxication should be admitted to the ICU for continuous monitoring of ECG. Administration of digitalis should be halted.  If serum potassium is below normal, administer K + salts and give antiarrhythmic drugs as Lidocain as ordered by Dr. Drug interactions:  Antacid (they decrease the effect of digitalis).  Fursemide (Lasix): it increase K + loss and increase the chance for digitalis toxicity.

Predisposing factors for digitalis toxicity: K + loss (hypokalemia) which results from: diuretics, NPO, gastric suction, and poor K + intake. Pathological conditions; Liver disease: they decrease metabolism and therefore increase digitalis level. Kidney disease: they decrease the excretion of drug and therefore increase digitalis levels.

Nursing considerations Check doctor’s order, medication record and bottle label accurately. Observe & monitor for evidence of bradycardia or arrhythmia. Measure intake and output accurately. Weigh the patient in daily basis. Pulse should be checked by 2 nurses. Provide the client with food high in potassium as banana, orange. Monitor serum digoxin level. Elderly people should be assessed for early signs of toxicity. Teach patients that bradyacadia, nausea, vomiting, diarrhea, loss of appetite, and visual disturbances could be early signs of toxicity. Teach client if heart rate is less than 60/minute to hold the medication and see the doctor. Have digoxin antidote available (digoxin immune FAB).

Drugs: 1. Digitoxin:crystodigin Class: cardiac glycoside Uses:drug of choice for maintenance in CHF. Dose:Digitalizing dose is 0.6 mg in 4-6 hours. Maintenance:0.05 – 0.3 mg/day. 2. Digoxin: Lanoxin Class: cardiac glycoside. It is the drug of choice for CHF because of: It has rapid onset. It has short duration. It can be administered P.O. or IV. Dose: digitalization dose = 0.4 – 0.6 mg followed by 0.05 – 0.35 mg once or twice daily.

3. Digoxin Immune FAB: (Ovine) Class: digoxin antidote. Action: antibodies bind to digoxin and excreted through the kidneys. Uses:life threatening digitalis toxicity or overdose. Note: cardiac arrest can be expected if an adult ingests 10 mg or if a child ingests 4 mg.