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Heart Failure Treatment (Part 2) (Loop diuretics (Drugs: Frusemide,…
Heart Failure Treatment
(Part 2)
Loop diuretics
Drugs:
Frusemide
Mechanism of action:
Inhibits the Na+/K+/2Cl- symporter in the thick ascending limb of the loop of Henle
This results in increased loss of Na+, K+, Cl- and water in urine causing a decrease in venous return & venous pooling
Clinical effects:
Decreased oedema
Decreased blood volume & BP
Adverse effects:
Orthostatic hypotension, dizziness, hypokalaemia, hyperuricaemia --> gout
Pharmacokinetics:
Less effective in renal impairment
Spironolactone
Mechanism of action:
Aldosterone antagonists inhibiting aldosterone-induced increase in Na+ channels & Na+/K+ATPase in the kidney lumen
This decreases K+ excretion & increases Na+ and water loss
Clinical effects:
Decreases blood volume & therefore BP
Clinical use:
Especially useful in heart failure by interrupting the RAA system
Adverse effects:
Hyperkalaemia (requires monitoring)
Gynaecomastia, menstrual disorders, testicular atrophy
Milrinone
Mechanism of action:
Inhibits phosphodiesterase-3 which normally metabolises cAMP in cardiac tissue
This causes an increase in cAMP --> increased force of myocardial contraction
Clinical effects:
Increased contractility
Clinical use:
Severe heart failure refractory to other treatment
Adverse effects:
Supraventricular & ventricular arrhythmias
Ivabradine
Mechanism of action:
Blocks hyperpolarisation-activated Na+ channels, thus inhibiting a current regulating the intervals between depolarisations
Clinical effects:
Reduced HR without reducing BP, conduction or contractility
Lowers myocardial O2 demand
Clinical use:
Considered for patients with chronic heart failure in sinus rhythm >77bpm
Adverse effects:
Bradycardia