MoA
Inhibits Na+/K+/Cl- co-transporter in the ascending limb of loop of Henle.
More detail:
- Responsible for transporting sodium, potassium and chloride ions from the lumen into cells.
- Water follows by osmosis.
- Inhibiting reabsorption = less water follows.
Indications
- Relief of breathlessness in acute pulmonary oedema in combination with O2 + nitrates.
- Fluid overload in chronic HF
- Fluid overload in other oedematic states (e.g. renal disease/liver failure)
How long do they take to work?
- 1 hour onset
- 6 hour duration
Acute pulmonary oedema
IV furosemide (40 mg)
Then, oral maintenance doses.
Side effects
- Dehydration
- Hypotension
- Low electrolyte state
- Ototoxicity (hearing loss/tinnitus)
Low electrolyte state
- Increased urinary loss of sodium, potassium and chloride ions indirectly increases excretion of magnesium, calcium and hydrogen.
- Hyponatraemia
- Hypokalaemia
- Hypochloraemia
- Hypomagnesaemia
- Metabolic alkalosis (hypocalcaemia)
Contraindications
Severe hypovolemia and dehydration
Cautions
Hypokalaemia
Hyponatraemia
People at risk of hepatic encelopathy
Gout (chronic use = inhibits uric acid secretion)
Diabetes (can cause hyperglycaemia BUT less likely than thiazides)
BPH (can cause urinary retention)
Interactions
Drugs that are renally excreted (e.g. lithium) - increases Cp levels of these drugs.
Digoxin - increased risk of toxicity due to diuretic-associated hypokalaemia
Aminoglycosides - increases risk of ototoxicity and nephrotoxicity
Heart failure
Furosemide = 20-40 mg OM. Can be increased up to 120 mg.
Can be taken BD if necessary, last dose taken at 4pm
Resistant hypertension
Bumetanide (most potent)
Torasemide (musculoskeletal pain)
Furosemide
Monitoring
Electrolytes
