CARDIOTONIC MEDICATIONS.docx

**Cardiotonic Medications** - Drugs used to increase the contractility of the heart muscle for patients experiencing heart failure. **Mechanism of Actions** - Inotropic drugs affect the intracellular calcium levels in the heart muscle, leading to increased contractility. - This inc...

**Cardiotonic Medications** - Drugs used to increase the contractility of the heart muscle for patients experiencing heart failure. **Mechanism of Actions** - Inotropic drugs affect the intracellular calcium levels in the heart muscle, leading to increased contractility. - This increase in contraction strength leads to increased cardiac output, which causes increased renal blood flow and increased urine production. - Increased renal blood flow decreases renin release, interfering with the effects of the RAAS, and increases urine output, leading to decreased blood volume. - The result is a decrease in the heart's workload and relief of HF. **1. Cardiac Glycosides** - Originally derived from the foxglove or digitalis plant. - These plants were once ground up to make digitalis leaf. - Digoxin (Lanoxin) is the drug most often used to treat heart failure. **Actions and Indications** - Digoxin increases intracellular calcium and allows more calcium to enter myocardial cells during depolarization. - These results to increased force of myocardial contraction (positive inotropic effect). Increased cardiac output and renal perfusion. - Slowed heart rate, owing to slowing of the rate of cellular repolarization (negative chronotropic effect) - Decreased conduction velocity through the atrioventricular (AV) node. - Indicated for the treatment of HF, atrial flutter, atrial fibrillation, and paroxysmal atrial tachycardia. - It has a very narrow margin of safety. **Pharmacokinetics** - It can be for oral and parenteral administration. - It has a rapid onset of action and rapid absorption (30--120 minutes when taken orally, 5--30 minutes when given intravenously). - Primarily excreted unchanged in the urine. - Because of this, caution should be exercised in the presence of renal impairment because the drug may not be excreted and could accumulate, causing toxicity. **Contraindications** - Patients with ventricular tachycardia or fibrillation, which are potentially fatal arrhythmias and should be treated with other drugs. - Heart block or sick sinus syndrome, which could be made worse by slowing of conduction through the AV node. - Renal insufficiency because the drug is excreted through the kidneys and toxic levels could develop. - Idiopathic hypertrophic subaortic stenosis (IHSS) because the increase in force of contraction could obstruct the outflow tract to the aorta and cause severe problems. - Acute MI because the increase in force of contraction could cause more muscle damage and infarct. - Electrolyte abnormalities (increased calcium, decreased potassium, decreased magnesium), which could alter the action potential and change the effects of the drug. **Adverse Effects** - Headache, weakness, drowsiness, and vision changes (a yellow halo around objects). - GI upset, anorexia, arrhythmias, ventricular tachycardia, malaise, depression. - ANTIDOTE: Digoxin Immune Fab (DigiFab). DIGOXIN immune Fab (DigiFab) is an **antigen-binding fragment (Fab)** derived from specific [antidigoxin anti-bodies.] These antibodies bind molecules of digoxin, making them [unavailable at their site of action.] The digoxin antibody-antigen complexes accumulate in the blood and are excreted through the kidney. Digoxin immune Fab is used for the treatment of life-threatening ***digoxin intoxication (serum levels\> 10ng/mL within serum potassium \>5 mEq/L*** in a setting of digoxin intoxication) and potential life-threatening digoxin overdose. The amount of digoxin immune Fab that is infusedintravenously is determined by the amount of digoxin ingested or by the serum digoxin level if the ingested amount is unknown. The ***patient's cardiac status should be monitored continually while the drug is given and for several hours after the infusion is finished.*** Because there is a risk of hypersensitivity reaction to the infused protein, ***life-support equipment should be on standby.*** Serum digoxin levels will be very high and unreliable for about 3 days after the digoxin immune Fab infusion because of the high levels of digoxin in the blood. ***[The patient should not be redigitalized for several days to 1 week after digoxin immune Fab has been use because of the potential of remaining fragments in the blood.]*** **Drug-Drug Indications** - Increased therapeutic effects and toxic if it is taken with verapamil, amiodarone, quinidine, quinine, erythromycin, tetracycline, or cyclosporine. - If combined with any of these drugs, it may be necessary to decrease the digoxin dose to prevent toxicity. - The risk of cardiac arrhythmias could increase if these drugs are taken with potassium-losing diuretics. Check potassium levels regularly. - Less effective if it is combined with thyroid hormones, metoclopramide, or penicillamine, and increased digoxin dose may be needed. - Absorption of oral digoxin may be decreased if it is taken with cholestyramine, charcoal, colestipol, antacids, bleomycin, cyclophosphamide, or methotrexate. - If it is used in combination with any of these agents, administer 2 to 4 hours apart. - St. John's wort and psyllium have been shown to decrease the effectiveness of digoxin. - Increased digoxin toxicity has been reported with ginseng, hawthorn, and licorice. **Nursing Diagnoses** Nursing diagnoses related to drug therapy might include the following: - Risk for Imbalanced Fluid Volume r/t to increased renal perfusion secondary to effects of the drug - Decreased Cardiac Output r/t ineffective cardiac muscle function - Ineffective Tissue Perfusion (Total Body) related to changes in cardiac output - Impaired Gas Exchange r/t changes in cardiac output. - Deficient Knowledge regarding drug therapy **Nursing Considerations** - Monitor apical pulse for 1 full minute before administering the drug. - Hold the dose if the pulse is less than 60 beats/min in an adult or less than 90 beats/min in an infant. - If the pulse remains low after one hour, withhold the drug, and notify the prescriber because this could indicate digoxin toxicity. - Administer IV doses very slowly over at least 5 minutes to avoid cardiac arrhythmias. - Avoid IM doses are painful. - Weight daily to rule out fluid retention and check for edema - Have the cardiac monitor standby, have potassium salts and lidocaine for arrtythmias, phenytoin for seizure, atrophine to increase heart rate. - Monitor the patient for therapeutic digoxin level (0.5--2 mg/mL). - Small, frequent meals to help alleviate GI upset or nausea, access to bathroom previlleges due to increased urination related to increased cardiac output. - Must have adequate room lighting due to vison changes (yellow halo around objects). **2. Phosphodiesterase Inhibitors** - It belongs to a second class of drugs that act as cardiotonic (inotropic) agents. - These include milrinone (Primacor). - Indicated for the short-term treatment of HF that has no or poor response to digoxin, diuretics, and vasodilators. **Mechanism of Action** - It blocks the enzyme phosphodiesterase that leads to an increase in myocardial cell cyclic adenosine monophosphate (cAMP), which increases calcium levels in the cell. - Increased cellular calcium causes a stronger contraction and prolongs the effects of sympathetic stimulation, which can lead to vasodilation, increased oxygen consumption, and arrhythmias. - Because these drugs have been associated with the development of potentially fatal ventricular arrhythmias, their use is limited to severe situations. **Pharmacokinetics** - Inamrinone and milrinone are available only for intravenous use. - These drugs are widely distributed after injection. - They are metabolized in the liver and excreted primarily in the urine. **Contraindications** - They also are contraindicated in the following conditions: severe aortic or pulmonic valvular disease. - Acute myocardial infarction, fluid volume deficit, and ventricular arrhythmias. - Caution in giving to elderlies. **Pharmacokinetics** - Ventricular arrhythmias, ventricular fibrillation, hypotension, and chest pain. - Nausea, vomiting, anorexia, and abdominal pain. - Thrombocytopenia and burning in the IV site. - Hypersensitivity reactions associated with these drugs include vasculitis, pericarditis, pleuritis, and ascites. **Drug-Drug Interactions** - Precipitates form when these drugs are given in solution with furosemide. - Avoid this combination in solution. - Use alternate lines if both of these drugs are being given intravenously. **Nursing Actions** - Protect the drug from light to prevent drug degradation. - Assess skin for signs of thrombocytopenia. - Check platelets regularly to check dose adequacy. - Watch closely BP and HR for toxicity. - Check IV site for burning or irritation. **Overall View** Cardiotonic medications, primarily used for heart failure, enhance heart muscle contractility. They work by increasing intracellular calcium, improving cardiac output and renal blood flow, which reduces the heart's workload. 1. **Cardiac Glycosides (e.g., Digoxin):** a. Derived from the foxglove plant, it increases myocardial contraction and slows heart rate. b. Indicated for heart failure and certain arrhythmias but has a narrow safety margin. c. Caution is needed in renal impairment due to toxicity risk. 2. **Phosphodiesterase Inhibitors (e.g., Milrinone):** d. Used for short-term heart failure management. e. Increases cAMP levels, enhancing contraction but may cause serious arrhythmias. **Adverse Effects:** Include gastrointestinal issues and visual disturbances. Digoxin toxicity can be treated with Digoxin Immune Fab, an effective antidote that neutralizes digoxin's effects. Monitoring is essential for safe administration. **Summary** Cardiotonic medications are essential for managing heart failure and other cardiac conditions by enhancing heart muscle contractility, thereby improving cardiac output and organ perfusion. **Importance of Understanding Cardiotonic Medications:** - They are critical in acute heart failure scenarios and chronic management, especially when other treatments fail. - These drugs increase intracellular calcium, leading to stronger heart contractions and reduced workload on the heart. - Knowledge of their narrow therapeutic index is vital to prevent toxicity, which can be life-threatening. - Understanding their role helps in tailoring patient-specific therapies and monitoring for adverse effects