What are the dosages, side effects, and teaching instructions for Furosemide (Lasix) and Digoxin (Digitalis)?

Furosemide and Digoxin: Dosing, Side Effects, and Patient Teaching

Furosemide (Lasix)

Dosing Recommendations

For acute decompensated heart failure, start with 20-40 mg IV in diuretic-naïve patients, or give at least the equivalent of the patient's oral dose if already on chronic diuretic therapy. 1

• Diuretic-naïve patients: Initial dose 20-40 mg IV furosemide 2, 1
• Patients on chronic oral diuretics: Initial IV dose should be at least equivalent to their oral maintenance dose 1, 3
• Oral maintenance dosing: Starting dose 20-40 mg daily, with maximum recommended daily dose of 250-500 mg 2
• Administration route: Can be given as intermittent boluses or continuous infusion, adjusted according to symptoms and clinical status 1, 3
• Dose titration: For cirrhotic ascites, combine with spironolactone in a 40 mg:100 mg ratio (furosemide:spironolactone), increasing every 3-5 days while maintaining this ratio up to maximum 160 mg furosemide and 400 mg spironolactone daily 2

Major Side Effects

Furosemide causes significant electrolyte disturbances that require close monitoring, particularly hypokalemia, hypomagnesemia, and hyponatremia. 2

• Electrolyte abnormalities: Hypokalemia, hypomagnesemia, hyponatremia 2
• Metabolic effects: Hyperuricemia, glucose intolerance, acid-base disturbances 2
• Cardiovascular: Orthostatic hypotension (aggravated by alcohol, barbiturates, or narcotics) 4
• Gastrointestinal: Pancreatitis, hepatic encephalopathy in hepatocellular insufficiency, nausea, vomiting, diarrhea, constipation 4
• Neurological: Tinnitus, hearing loss, vertigo, dizziness, headache, blurred vision 4
• Hematologic: Aplastic anemia, thrombocytopenia, agranulocytosis, leukopenia 4
• Severe hypersensitivity: Anaphylactic reactions, systemic vasculitis, interstitial nephritis, Stevens-Johnson Syndrome, toxic epidermal necrolysis 4
• Dermatologic: Photosensitivity, rash, pruritus, urticaria 4

Monitoring Requirements

Monitor serum creatinine and potassium every 5-7 days after initiation until stable, then every 3-6 months. 2

• Initial monitoring: Check symptoms, urine output, renal function, and electrolytes regularly during IV therapy 1, 3
• Frequency: Measure serum creatinine and potassium every 5-7 days after starting treatment until values stabilize 2
• Long-term monitoring: After stabilization, check every 3-6 months 2
• Consider bladder catheterization: To accurately monitor urinary output and rapidly assess treatment response 1

Patient Teaching

Teach patients to take furosemide in the morning to avoid nighttime urination, monitor daily weights, and report signs of dehydration or electrolyte imbalance immediately. 2, 3

• Timing: Take single morning dose to maximize compliance and minimize nighttime urination 2
• Daily weights: Monitor weight daily; target weight loss of 0.5-1.0 kg daily to avoid excessive diuresis 5
• Fluid intake: In severe hyponatremia (sodium <120-125 mmol/L), fluid restriction may be necessary 2
• Warning signs to report: Dizziness, lightheadedness, muscle cramps, weakness, excessive thirst, confusion, or decreased urination 4
• Orthostatic precautions: Rise slowly from sitting or lying positions to prevent falls from orthostatic hypotension 4
• Avoid: Alcohol, which can worsen orthostatic hypotension 4
• Sun protection: Use sunscreen due to photosensitivity risk 4

Critical Clinical Pitfalls

Patients with hypotension (SBP <90 mmHg), severe hyponatremia, or acidosis are unlikely to respond well to diuretic treatment. 1

• Poor responders: Hypotension, severe hyponatremia, or acidosis predict inadequate diuretic response 1
• High-dose risks: Excessive diuresis can cause hypovolemia, hyponatremia, and increase likelihood of hypotension when initiating ACE inhibitors or ARBs 1
• Not monotherapy: Diuretics should not be used alone in chronic heart failure but combined with other guideline-directed medical therapy 3
• Oral bioavailability: Good oral bioavailability in cirrhotic patients favors oral over IV route; IV furosemide causes acute GFR reductions 2

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Digoxin (Digitalis)

Dosing Recommendations

Start digoxin at 0.125-0.25 mg daily, adjusting the dose to achieve a therapeutic serum concentration of 0.5 to <0.9 ng/mL. 2, 6

• Initial dose: 0.125-0.25 mg daily (modified according to patient factors) 2, 6
• Target serum concentration: 0.5 to <0.9 ng/mL 2
• Dose individualization factors: Body weight (use lean/ideal body weight), renal function (creatinine clearance), age, concomitant medications 6
• Advanced age consideration: May indicate diminished renal function even with normal serum creatinine (<1.5 mg/dL) 6

Therapeutic Drug Monitoring

Draw digoxin levels at least 6-8 hours after the last dose, ideally just before the next scheduled dose, to allow adequate tissue equilibration. 6

• Timing of blood draw: Just before next scheduled dose is optimal; if not possible, wait at least 6-8 hours after last dose 6
• Concentration variation: On once-daily dosing, levels will be 10-25% lower at 24 hours versus 8 hours post-dose, depending on renal function 6
• Therapeutic range: About two-thirds of adequately digitalized patients have levels of 0.8-2.0 ng/mL 6
• Toxicity correlation: About two-thirds of patients with clinical toxicity have levels >2.0 ng/mL, but one-third have levels <2.0 ng/mL 6
• Clinical context: Always interpret serum concentration in overall clinical context; isolated measurements should not solely determine dose adjustments 6

Indications in Heart Failure

Digoxin is indicated for atrial fibrillation with any degree of symptomatic heart failure to slow ventricular rate and improve symptoms. 2

• Primary indication: Atrial fibrillation with symptomatic heart failure of any degree 2
• Mechanism: Slows ventricular rate, improving ventricular function and symptoms 2
• Level of evidence: Class I recommendation, Level B evidence 2

Major Side Effects and Toxicity

Digoxin toxicity can occur even at therapeutic levels in some patients, presenting with gastrointestinal, cardiac, and neurological symptoms. 6

• Individual sensitivity: Rare patients cannot tolerate digoxin at levels below 0.8 ng/mL 6
• Toxicity threshold: Two-thirds of toxic patients have levels >2.0 ng/mL, but toxicity can occur at lower levels 6
• Common toxic manifestations: Gastrointestinal symptoms (nausea, vomiting, anorexia), cardiac arrhythmias, visual disturbances (yellow-green vision), confusion, weakness 6

Drug Interactions

Furosemide does not significantly affect digoxin excretion or serum levels when renal function is normal. 7, 8

• No dose adjustment needed: Furosemide does not alter digoxin renal clearance or serum concentrations in patients with normal renal function 7, 8
• Electrolyte monitoring: However, furosemide-induced hypokalemia can increase digoxin toxicity risk, requiring careful electrolyte monitoring 2

Patient Teaching

Teach patients to check their pulse before each dose and report rates below 60 bpm or above 100 bpm, along with any signs of toxicity. 6

• Pulse monitoring: Check pulse before each dose; hold dose and call provider if heart rate <60 or >100 bpm
• Signs of toxicity to report: Nausea, vomiting, loss of appetite, visual changes (yellow-green halos), confusion, unusual fatigue, palpitations 6
• Consistent timing: Take at same time each day to maintain steady levels
• Do not double doses: If a dose is missed, do not take two doses to make up for it
• Electrolyte awareness: Report symptoms of low potassium (muscle weakness, cramps, irregular heartbeat) as this increases toxicity risk 2
• Drug interactions: Inform all healthcare providers about digoxin use, as many medications can interact

Critical Clinical Pitfalls

Discrepancies between serum digoxin concentration and clinical response should prompt investigation of analytical problems, sampling timing, or altered patient sensitivity. 6

• Investigate discrepancies: Consider analytical assay problems, inappropriate sampling time, administration of other digitalis glycosides, or conditions altering patient sensitivity 6
• Exercise effect: Serum digoxin may decrease acutely during exercise due to increased skeletal muscle binding, without change in clinical efficacy 6
• Renal impairment: Requires significant dose reduction; calculate creatinine clearance for proper dosing 6
• Elderly patients: May have reduced renal function despite normal serum creatinine, requiring lower doses 6