Pharma

• Heart Failure (HF)


  Complex, progressive disorder where the heart is unable to pump sufficient blood to meet the needs of the body

  
• Symptoms of Heart Failure


  • Dyspnea (shortness of breath)
  • Fatigue
  • Fluid retention

  
• Impaired ability of the heart

  Inadequate filling with and/or ejection of blood

  
• Underlying causes of HF

  • Arteriosclerotic heart disease
  • Myocardial infarction
  • Hypertensive heart disease
  • Valvular heart disease
  • Congenital heart disease

  
• Chronic activation of the sympathetic nervous system and the renin–angiotensin–aldosterone system

  • Remodeling of Cardiac Tissue
  • Loss of Myocytes
  • Hypertrophy
  • Fibrosis

  
• Remodeling, loss of myocytes, hypertrophy, fibrosis

  Prompts additional neuro-hormonal activation
• If left untreated, leads to death
• Goals of Pharmacologic Intervention in HF

  • Alleviate Symptoms
  • Slow Disease Progression
  • Improve Survival
• Seven Classes of Drugs

  • Angiotensin-converting Enzyme Inhibitors
  • Angiotensin-receptor Blockers
  • Aldosterone antagonists
  • β-blockers
  • Diuretics
  • Direct Vaso- and Venodilators
  • Inotropic agents

  
• Depending on the severity of HF individual patient factors, one or more of these classes of drugs are administered
• Pharmacologic Intervention Provides


  • Reduced Myocardial Work Load
  • Decreased Extracellular Fluid Volume
  • Improved Cardiac Contractility
  • A Reduced rate of cardiac remodeling
• Therapeutic Strategies in HF

  • Fluid limitations (less than 1.5 to 2 L daily)
  • Low dietary intake of sodium (less than 2000 mg/d)
  • Treatment of comorbid conditions
  • Use of diuretics
  • Avoid drugs that may precipitate or exacerbate HF
  • Inhibitors of the renin–angiotensin–aldosterone system
  • Inhibitors of the sympathetic nervous system
  • Inotropic agents are reserved for acute HF signs and symptoms in mostly the inpatient setting

  
• Inotropic Drugs


  Enhance cardiac contractility and increase cardiac output
• All positive inotropes in HFrEF that increase intracellular calcium concentration have been associated with reduced survival

  
• Inotropic agents, except for digoxin, are only used for a short period mainly in the inpatient setting
• Digitalis Glycosides


  Increase the heart muscle contractility and are used in treating HF

  
• Digoxin


  The most widely used cardiac glycoside agent

  
• Mechanism of Action of Digoxin

  • Increases the force of cardiac contraction, causing cardiac output to more closely resemble that of the normal heart
  • Enhances vagal tone, decreasing heart rate and myocardial oxygen demand
  • Slows conduction velocity through the AV node, making it useful for atrial fibrillation

  
• Low-dose digoxin


  Inhibits sympathetic activation with minimal effects on contractility
• Digoxin therapy is indicated in patients with severe HFrEF after initiation of ACE inhibitor, β-blocker, and diuretic therapy

  
• A low serum drug concentration of digoxin (0.5 to 0.8 ng/mL) is beneficial in HFrEF
• At higher serum drug concentrations, admissions are prevented, but mortality likely increases

  
• Digoxin is not indicated in patients with diastolic or right-sided HF unless the patient has concomitant atrial fibrillation or flutter

  
• Patients with mild to moderate HF often respond to treatment with ACE inhibitors, β-blockers, aldosterone antagonists, direct vaso- and veno-dilators, and diuretics and may not require digoxin

  
• Pharmacokinetics of Digoxin


  • Available in oral and injectable formulations
  • Has a large volume of distribution, accumulating in muscle
  • Has a long half-life of 30 to 40 hours
  • Mainly eliminated intact by the kidney, requiring dose adjustment in renal dysfunction
• Adverse Effects of Digoxin

  • At low serum drug concentrations, digoxin is fairly well tolerated
  • Has a very narrow therapeutic index, and digoxin toxicity is one of the most common adverse drug reactions leading to hospitalization
  • Anorexia, nausea, and vomiting may be initial indicators of toxicity
  • Patients may also experience blurred vision and various cardiac arrhythmias

  
• Management of Digoxin Toxicity

  • Discontinuing digoxin
  • Determining serum potassium levels, and, if indicated, replacing potassium
  • Severe toxicity resulting in ventricular tachycardia may require the administration of antiarrhythmic drugs and the use of antibodies to digoxin (digoxin immune Fab)
• With the use of a lower serum drug concentration in HFrEF, toxic levels are infrequent
• Clarithromycin, Verapamil, and Amiodarone, can significantly increase digoxin levels, necessitating a reduced dose of digoxin

  
• Digoxin should also be used with caution with other drugs that slow AV conduction, such as β-blockers, verapamil, and diltiazem

  
• β-Adrenergic agonists


  Dobutamine and Dopamine improve cardiac performance by causing positive inotropic effects and vasodilation

  
• Mechanism of Action of β-Adrenergic agonists

  Lead to an increase in intracellular cyclic adenosine monophosphate (cAMP), which results in the activation of protein kinase, thereby increasing the entry of calcium ions into the myocardial cells and enhancing contraction

  
• Both dobutamine and dopamine must be given by intravenous infusion and are primarily used in the short-term treatment of acute HF in the inpatient setting

  
• Serum drug concentration


  Lower concentration in HFrEF leads to infrequent toxic levels
• Clarithromycin, Verapamil, and Amiodarone

  Can significantly increase digoxin levels, necessitating a reduced dose of digoxin

  
• Digoxin


  Should be used with caution with other drugs that slow AV conduction, such as β-blockers, verapamil, and diltiazem

  
• ↓digit 80 & 2003 & 214%
• β-Adrenergic agonists


  • Dobutamine and Dopamine improve cardiac performance by causing positive inotropic effects and vasodilation
  • Dobutamine is the most commonly used inotropic agent other than digoxin

  
• Mechanism of β-Adrenergic agonists

  1. Increase intracellular cyclic adenosine monophosphate (cAMP)

  2. Activation of protein kinase

  3. Phosphorylation of slow calcium channels

  4. Increased entry of calcium ions into the myocardial cells

  5. Enhanced contraction

  
• β-Adrenergic agonists


  Must be given by intravenous infusion and are primarily used in the short-term treatment of acute HF in the hospital setting