Drugs for Heart Failure 2 Flashcards
What is the effect of beta blockers?
- reduces heart rate and oxygen consumption
- cardiac output is increased after several months
- chance of irregular heart beat reduced
- mortality reduced post MI-> treatment of choice post-infarct
What are the benefits of beta-adrenergic receptor blockade?
- decrease adverse effects of high catecholamine levels on the heart
- decreased cardiomyocyte apoptosis (cell death)
- decreased cardiac remodelling (decreased mitogenic activity)
- — mechanism is not completely understood
Describe the action of carvedilol?
- blocks beta and alpha adrenergic receptors
- alpha adrenergic receptor blockade helps to relax (dilate) arteries
- the heart does not have to work as hard to eject blood (decreased after load)
- beta adrenergic receptor blockade slows the heart and decreases force of contraction
- first line treatment in heart failure
What is the main difference between metoprolol and carvedilol?
– metoprolol selectively blocks beta 1 adrenergic receptors
Beta blockers should be avoided in what conditions?
- avoid in asthma, COPD, peripheral vascular disease, insulin dependent diabetes, physically active
What diseases are beta blockers mostly used in?
- hypertension
- glaucoma
- certain arrhythmia
- MI
- angina
What is the drug interaction between carvedilol and ventolin?
- interaction with ventolin worsens breathing problems due to a narrowing of the airways
What is the interaction between carvedilol/metoprolol and verapamil?
interaction can cause an irregular heart beat
Antiretroviral medications can cause an _____
arrhythmia
Why is alcohol dangerous to take with blood pressure lowering agents?
- has an additive effect on lowering blood pressure
What is the action of ionotropes?
- alter the force of contraction of the heart (increase contraction)
- positive ionotropes are of interest here
What is the effect of long term use of ionotropes?
- increased mortality
What are the 2 examples of ionotropes?
-digoxin and dobutamine
Explain the mechanism of action of dobutamine?
- must be given via IV
- stimulates beta adrenergic receptors in the heart to increase heart rate and more importantly contractility
- must carefully monitor- may increase heart rate, myocardial oxygen consumption and blood pressure
- may aggravate ischemia and promote arrhythmias
Explain the mechanism of digoxin?
- increases heart contractility (increases calcium release in myocardial cells)
- blocks Na/K ATPase
- must closely monitor (can increase heart rate, myocardial O2 consumption, BP. Can also aggravate schema and provoke arrhythmias)
What is the symptomatic improvement that digoxin provides?
- improved exercise capacity and decreased hospitalization for heart failure
When taking digoxin, it is important to monitor ____ levels
potassium
(hypokalemia increases digoxin toxicity, as both inhibit the Na/K ATPase
What drugs must you be careful with when giving digoxin?
- diuretics: may produce hypokalemia (increases digoxin toxicity)
- ACEIs/ARBs or B-adrenegric receptor antagonists: may increase potassium levels
- Potassium sparing diuretics: do not cause hypokalemia, not as good at increasing sodium excretion
- interactions with some medications can dangerously increase blood levels of digoxin resulting in cardiac arrhythmias (antibiotics such as amoxicillin and erythromycin, amiodarone)
What is the action of the proximal tubule of the kidney?
- reabsorbs almost all glucose and amino acids and about 60% of sodium
- Na is reabsorbed through a Na/K ATPase
- CL exchanged for formate or oxalate anions
- water follows passively to maintain osmolarity
What ist he action of the ascending loop of henle?
- impermeable to water
- Na/K/2Cl co-transporter reabsorbs 30% of these ions
What is the action of the collecting tubule and duct?
- reabsorbs Na and water from the urine and secretes K
- Na/K ATPast is performing this function
What is the primary site of action of thiazide diuretics?
distal tubule
What happens in the distal tubule when a thiazide diuretic is added as a treatment option?
- inhibition of the Na/Cl transporter
- decreasing Na/Cl reabsorption (increase in Na excretion)
- increase in Ca reabsorption (decrease in Ca excretion)
What are the main problems associated with thiazide diuretics?
- hypokalemia- increased Na in urine at distal tubule causes more K to be exchanged for Na causing loss of K from the body
- hyperglycemia - problem for type 2 diabetes (decreases insulin release, decreases tissue utilization)
- increase in LDL levels
- increased incidence of erectile dysfunction
- volume contraction
- interaction with the anti-arrhythmic agent amiodarone can lead to a more irregular heartbeat
What are the advantages of using a thiazide diuretic over other medications to treat blood pressure?
- orally active
- no postural hypertension
- potentiate other anti-hypertensives
What do thiazide diuretics do to K? Uric acid? BP? Na? Ca?
K: due to increased aldosterone - sodium reabsorption at expense of potassium loss
Uric acid: increases
BP: decreses
Na: lowers due to the direct effect to increase sodium excretion
Ca: due to direct effect to decrease calcium excretion
What is the mechanism of action of loop diuretics?
- inhibit the Na/K/2Cl co-transporter in the ascending loop of henle
- very potent and efficacious- high ceiling diuretics. Up to 20% of the filtered load if excreted
- prostaglandins are very important - useful in acute pulmonary edema
- increases Na, Cl, K, Mg and Ca excretion (note Ca effect)
The effect on ___ is opposite in loop diuretics and thiazide diuretics?
calcium
What are the main side effects of loop diuretics?
- deafness and kidney damage - never combine loop diuretics with amino glycoside antibiotics
- interaction with the antiarrhythmatic agent amiodarone can lead to a more irregular heartbeat
When are loop diuretics typically used?
- preferred in renal insufficiency
- glomerular filtration rate of under 50 ml/min
- edema, hypertension, hypercalcemia, heart failure
Describe potassium sparing diuretics?
- weak diuretics
- give with other diuretics to decrease potassium loss
- may cause hyperkalemia
- never combine with K supplements
Describe the action of spironolactone
- aldosterone receptor antagonists
- prevents aldosterone from binding to the receptor
(decreases sodium reabsorption, decreases potassium excretion) - may cause hyperkalemia
- prevents cardiac remodeling associated with high levels of aldosterone in heart failure
How potassium sparing diuretics manage ___ is opposite of loop and thiazide diuretics
K
What are the steps of managing a patient with heart failure?
- managing conditions that contribute to heart failure (hypertension, diabetes, lipids)
- diet physical activity and lifestyle changes
1. start with ACEI or Beta-adrenegeric receptor blockade (lowers bp and reduces stress on the heart)
2. Diuretic- in patients with edema (remove excess fluids and sodium from the body)
3. Extreme failure- add an ionotrope (increases contractility to alleviate heart failure symptoms)
Beta blockers are only started once patients are _____ on ACEI- should start at a low dose
stable
Describe the different stages of heart failure (A-D)
A: High risk heart failure with no symptoms
B: Structural heart disease, no symptoms
C: structural heart disease, previous or current symptoms
Stage D: end stage-just trying to improve quality of life
