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Chronotropic drugs
  • affects the heart rate
  • if the drug accelerates the heart rate, it is said to have a positive chronotropic effect (isopreterenol [Isuprel], epinephrine) and vice versa (verapamil [Isoptin])
dromotropic drugs
  • affects conduction velocity through the conducting tissues of the heart
  • if a drug speeds conduction, it is said to have a positive dromotropic effect (isoproterenol [Isuprel], phenytoin [Dilantin] and vice versa (verapamil [Isoptin], adenosine [Adenocard])
Inotropic drugs
  • strenghtens or increases the force of cardiac contraction (positive inotropic effect). [3.g., digoxin (Lanoxin), dobutamine (Dobutrex), epinephrine, isoproterenol (Isuprel)]
  • a drug that weakens the force of cardiac contraction has a negative inotropic effect. [propranolol (inderal)]
Drugs Used to Treat Dysrhythmias
  • Adenosine (Adnocard)
  • Amiodarone (Codarone)
  • Atropine
  • Dopamin (Intropin)
  • Isoproterenol (Isuprel)
  • Lidocaine (Xylocaine
  • Magnesium
  • Procainamide (Pronestyl)
  • Beta-adrenergic blockers (Atenolol [Tenormin], Metoprolol [Lopressor, Toprol-XL])
  • Calcium channel blockers (Diltiazem [Cardizem], Verapamil [Isoptin])
Drugs used to optimize cardiac output and blood pressure
  • Calcium chloride
  • Digoxin (Lanoxin)
  • Dobuatamine (Dobutrex)
  • Dopamine (Intropin)
  • Epinephrine (Adrnalin)
  • Furosemide (Lasix)
  • Nitroglycerine (Nitrostat, Tridil)
  • Norepinephrine (Levophed)
  • Sodium Bicarbonate
  • Vasopressin (Pitressin)
cardiac glycosides
  • naturally occuring plant
  • example: digoxin (Lanoxin)
  • block certain ionic pumps in the cellular membrane
  • increases calcium concentration to the contractile proteins
  • negative chronotropic effect
  • negative dromotropic effect
  • positive inotropic effect
  • small therapeutic index
  • contains a carbohydrated molecule, that when is combined with water it is converted into sugar and one or more active substances
side effects of cardiac glycosides
  • flu-like symptoms
  • anorexia
  • nausea
  • vomiting
  • visual disturbances (flashing lights, altered color vision)
  • cardiac rhythm disturbances (usually slowing with varying degrees of blocked conduction)
digoxin
  • used to treat heart failure and to manage certain tachycardias
toxic effects of cardiac glycosides
  • dose related
  • may be increased by the presence of other drugs, such as diuretics
  • signs and symptoms are dysrhythmias (bradycardia, tachycardia, ventricular fibrillation)
  • treatment may include correction of electrolyte imbalance, neutralization of the free drug, and use of antidysrhythmics.
proarrhythmias
  • generated by antidysrhythmic agents
  • the sequential use of two or more antidysrhythmic drugs compound these effects
  • as a rule, use of no more than one agent is best to manage dysrhythmias unless use of morte than one is absolutely necessary
  • all antidysrhythmic drugs have some degree of proarrhythmic effect.
antidysrhythmics
  • used to treat and prevent disorders of cardiac rhytms
  • works by direct action on the cardiac cell membrane (lidocaine), indirect action that effects the cell (propranolol), or both
causes of cardiac rhythm disturbances
  • ischemia
  • hypoxia
  • acid/base imbalances
  • electrolyte embalance (potassium, calcium, sodium)
  • drug toxicity
  • catecholamine increases
  • scarred or diseased cardiac tissue
  • dysrhythmias result from disturbances in impulse formation, disturbances in impulse conduction or both
antidysrhythmics classifications
  • based on mode of action on cardiac muscle
  • drugs that belong to the same class do not produce identical actions
  • all antidysrhythmics have some ability to suppress automaticity (heart's ability to initiate an impulse, heart need to be health with K, NA, CA
  • Class I (A,B, and C), II, III, and IV
Class I antidysrhythmics
  • Sodium Channel Blockers
  • Works to slow conduction
  • divided into A, B, and C
  • examplle is lidocaine (Xylocaine)
  • Class A decreses conduction velocity and prolongs electical potential of cardiac tissue
  • Class B decreases or has no effect on conduction velocity
  • Class C profoundly slows conduction and are indicated only for control of life-threatening ventricular dysrhythmias
Class II antidysrhythmics
  • beta-blocking agents
  • reduce adrenergic stimulation of the heart
  • examples: labetalol hcl, propranolol
Class III antidysrhythmics
  • potassium channel blockers
  • increases contractility
  • does not suppress automaticity
  • no effect on conduction belocity
  • ceases dysrhytmias that result from the reentry of blocked impulses
  • example: amiodarone (Cordarone)
Class IV antidysrhytmics
  • calcium channel blockers
  • blocks the inflow of calcium through the cell membrane of the cardiac and smooth muscles
  • depresses the myocardial smooth muscle contraction
  • decreases automaticity
  • in some cases decreases conduction velocity
  • examples: verapamil (Isoptin), diltiazem (Cardizem)
antihypertensives
  • matain blood pressure within normal limits for various body positions
  • maintain or improve blood flow without compromising tissue perfusion or blood supply to the brain
  • reduce workload of the heart
  • have no undesirable effects
  • permit long term use with intolerance
  • classifications: diuretics, sympathetic blocking agents (sympatholic drugs), vasodilators, angiotensin-converting enzyme (ACE) inhibitors
  • calcium channel blockers
  • angiotensin II receptor antagonists
diuretics
  • drug of choice in managing hypertension
  • often used with other hypertensive agents
  • causes renal excretion of excess salt and water
  • decreases in plasma and ecf volume decreases preload and stroke volume
  • decrease in fluid volume has a direct effect on arterioles, reulting in lowered blood pressure
  • initial decline in cardiac output then a decrease in peripheral vascular resistance
thiazine diuretics
  • moderately effective in lowering blood pressure
  • example: HCTZ
  • may be given with another hypertensive to prevent the retention of sodium and water
loop diuretics
  • strong
  • short-acting agents
  • inhibits sodium and chloride reabsorption in the loop of Henle
  • cause excessive potassium loss
  • cause increase in the excretion of sodium and water
  • fewer side effects than most other antihypertensives
  • prescribed to patients with renal insufficiency
  • example: furosemide (Lasix)
potassium-sparring diuretics
  • effective as an antihypertensive when they are used in combination with other diuretics
  • promotes sodium and water loss without a loss of potassium
  • can treat some edematous states (cirrhosis of the liver)
  • example: spironolactone (Aldactone)
sympathetic blocking agents
  • classified as beta blocking and adrenergic inhibiting
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