💊
Furosemide (Lasix) Clinical Suite
Evidence-based · Adult & Pediatric · PO / IV / IM · Amp: 20 mg/2 mL · 10 mg/mL
Clinical Modifiers
Loop diuretic naïve
Diuretic resistance
Hypoalbuminemia
Elderly (≥ 65 yrs)
📊 Dosing RecommendationEvidence-Based
—
🔁 Oral ↔ IV Converter
🧪 Urine Output Target
📊 Ceiling Dose Estimator
💉 Infusion Dilution Builder
⚡ Electrolyte Loss Estimator
ℹ️
Equipotent equivalents to Furosemide 40 mg PO. Starting estimates — titrate to clinical response.
Furosemide
Lasix · Reference
Equiv. PO40 mg
Equiv. IV20 mg
Bioavailability50–60%
Duration PO/IV6–8h / 2h
Torsemide
Preferred in HF
Equiv. PO10–20 mg
Equiv. IV10–20 mg
Bioavailability80–90% ✓
Duration PO/IV12–16h / 6h
Bumetanide
40× Potent
Equiv. PO1 mg
Equiv. IV1 mg
Bioavailability~80% ✓
Duration PO/IV4–6h / 2–3h
Ethacrynic Acid
Sulfa-free
Equiv. PO50 mg
Equiv. IV50 mg
Bioavailability~100% ✓
Duration PO/IV6–8h / 2h
Interactive Converter
| Drug & Route | Equiv. Dose | Note |
|---|
⚠️
Starting estimates. PO:IV = 2:1 for furosemide; ~1:1 for torsemide & bumetanide.
Key Differences
| Feature | Furosemide | Torsemide | Bumetanide | Ethacrynic |
|---|---|---|---|---|
| PO bioavailability | 50–60% | 80–90% | ~80% | ~100% |
| Potency vs furo | 1× | 2–4× | 40× | ~1× |
| PO:IV ratio | 2:1 | ~1:1 | ~1:1 | ~1:1 |
| Duration | 6–8 h | 12–16 h | 4–6 h | 6–8 h |
| Sulfonamide | Yes | Yes | Yes | No ✓ |
| HF evidence | Standard | TRANSFORM-HF ✓ | Limited | Limited |
| Ototoxicity | ++ | + | + | +++ |
ℹ️
Estimates K⁺ deficit and replacement dose. Always confirm with repeat levels. IV requires cardiac monitoring.
⚡ K⁺ Replacement PlanIndividualized
—
K⁺ Severity Reference
| Serum K⁺ | Severity | Est. Deficit | Approach |
|---|---|---|---|
| 3.5–5.0 | Normal | — | Dietary K⁺ |
| 3.0–3.4 | Mild | ~100–200 mEq | Oral KCl preferred |
| 2.5–2.9 | Moderate | ~200–400 mEq | Oral ± IV |
| <2.5 | Severe | >400 mEq | IV mandatory · Cardiac monitor |
IV KCl Rules
| Parameter | Peripheral | Central |
|---|---|---|
| Max conc. | 40 mEq/100 mL | 200 mEq/100 mL |
| Max rate | 10 mEq/h | 20–40 mEq/h (ICU) |
| Max/session | 40 mEq over 4h | 40–80 mEq |
| Monitoring | Cardiac monitor · Recheck K⁺ after each 40 mEq · Never IV push | |
ℹ️
Definition: UO <100 mL/h after 2h of IV furosemide, or <1 mL/kg/h despite adequate dosing.
1
Confirm True Resistance
Check compliance · Na <2 g/day · Rule out NSAIDs · MAP >65 mmHg · Exclude pseudo-resistance
Assess first
2
Optimize Dose
Double dose if no response after 1–2h · Switch to IV · Ensure ceiling dose reached for patient's eGFR
Dose optimization
3
Switch to Continuous Infusion
Loading 40–80 mg IV → Maintenance 10–40 mg/h → ↑ 5–10 mg/h Q2h → Target UO ≥1 mL/kg/h
Step-up
4
Add Thiazide — Sequential Nephron Blockade
Chlorothiazide 250–500 mg IV Q12h · OR Metolazone 2.5–10 mg PO 30 min before furosemide
Combination
5
Address Hypoalbuminemia
Albumin <2.5 g/dL → Albumin 25 g IV → immediately furosemide 40–80 mg IV
If applicable
6
Add Acetazolamide
500 mg IV QD · For metabolic alkalosis · ADVOR trial: benefit in decompensated HF
Advanced
7
Ultrafiltration / RRT
If all pharmacological steps fail · Severe volume overload unresponsive to diuretics
Last resort
⚠️
Monitor during combination therapy: electrolyte disturbances, prerenal AKI. BMP Q8–12h.
Baseline
BMP · Mg²⁺ · Ca²⁺ · Phosphate · UA · BG · BP · HR · Weight
1–2 h IV
UO ≥200 mL/h · BP · Response vs. resistance
Q8–12 h
K⁺ · Mg²⁺ · BUN · Creatinine · Hourly UO · Daily weight
Daily
Full BMP · Weight (0.5–1 kg/day loss) · Net fluid balance · Orthostatic BP
Weekly
BMP · Mg²⁺ · UA · K⁺ supplementation · Renal trend
Prolonged
Audiometry (ototoxicity) · Thiamine in chronic HF
Response Assessment
| Timepoint | UO | Result | Action |
|---|---|---|---|
| 1h post IV | >200 mL | Good | Continue |
| 1h post IV | 100–200 mL | Partial | ↑ dose |
| 1h post IV | <100 mL | Poor | → Resistance |
| 24h | 0.5–1 kg loss | On target | Continue |
| 24h | >1 kg loss | Over-diuresis | Reduce or hold |
Electrolyte Targets
| Electrolyte | Target | Action if Low |
|---|---|---|
| K⁺ | >3.5 mEq/L | KCl supplement · K-sparing diuretic |
| Mg²⁺ | >0.8 mmol/L | Mg sulfate IV or Mg oxide PO |
| Na⁺ | 135–145 mEq/L | Water restrict if hyponatremic |
| HCO₃⁻ | 22–26 mEq/L | Metabolic alkalosis → Acetazolamide |
🤰 Pregnancy
| FDA Category | C |
| 1st trimester | Avoid if possible |
| 2nd–3rd trimester | Lowest effective dose · Monitor fetal growth |
| Acceptable for | Pulmonary edema · NYHA III–IV · Hypertensive crisis |
| Fetal risks | Electrolyte imbalance · Possible ototoxicity · Neonatal thrombocytopenia (rare) |
🤱 Breastfeeding
| Transfer | Low amounts |
| Concern | May suppress lactation · Infant electrolyte effects |
| Recommendation | Avoid if possible · Lowest dose · Monitor infant |
👶 Neonates & Premature
| Parameter | Detail |
|---|---|
| IV / IM dose | 0.5–1 mg/kg · Max 2 mg/kg · Q12–24h |
| Oral dose | 1–4 mg/kg · Q12–24h · Bioavailability ~20% |
| Nephrocalcinosis | Risk ↑ <32 wks · Renal US Q4–8 wks |
| PDA | May worsen via ↑ renal prostaglandins |
👴 Elderly (≥ 65 years)
| Start | 20 mg/day — titrate cautiously |
| Key risks | Orthostatic hypotension · Falls · Electrolyte disturbances |
| Beers Criteria | Listed — avoid as 1st-line antihypertensive |
🫀 Cirrhosis
| Max dose | 160 mg/day · Always + spironolactone |
| Ratio | Furosemide:Spiro = 1:2.5 (40 mg : 100 mg) |
| Weight loss target | ≤0.5 kg/day (no edema) · ≤1 kg/day (with edema) |
| Avoid | Rapid diuresis · NSAIDs · High doses without spironolactone |
💉 IV Preparation & Stability — Complete Reference
📌 Ampule Specification
Concentration20 mg / 2 mL = 10 mg/mL
pH8.0–9.3 (alkaline)
AppearanceClear, colorless · Discard if discolored
StorageRoom temperature · Protect from light
🔵 IV Bolus (Intermittent)
DiluentNS (preferred) or D5W · Undiluted OK if dose ≤ 40 mg
Volume≤ 40 mg → undiluted (≤ 4 mL)
> 40 mg → dilute in 50–100 mL NS or D5W
> 40 mg → dilute in 50–100 mL NS or D5W
Final conc.≤ 10 mg/mL undiluted · Aim 1–5 mg/mL when diluting
Max rate4 mg/min = 0.4 mL/min (adult) · 0.5 mg/kg/min (peds)
Min time20 mg → ≥5 min · 40 mg → ≥10 min · 80 mg → ≥20 min · 200 mg → ≥50 min
StabilityIn NS: 24 h RT · In D5W: 24 h RT · Protect from light
🟢 IV Continuous Infusion
Loading dose40–80 mg IV bolus first, then start infusion
DiluentNS (preferred) or D5W · Do NOT use LR
VolumeDilute in 100–250 mL NS or D5W
Final conc.≤ 2 mg/mL · e.g. 200 mg in 100 mL ✓
Starting rate10–20 mg/h → ↑ 5–10 mg/h Q2h → Max 40 mg/h
StabilityIn NS: 24 h RT · In D5W: 24 h RT · Protect from light throughout
🟡 IM Injection
PreparationGive undiluted (10 mg/mL) · Max 20 mg per site
Onset~30 min · Not preferred if IV access available
StabilityUse immediately · Do not store drawn-up syringe
⚠️ pH 8–9.3 — incompatible with acidic solutions. Do NOT mix with: amiodarone, ciprofloxacin, dobutamine, dopamine, gentamicin, milrinone. Compatible with: NS, D5W, morphine, KCl in NS.
Adult Dosing by Indication
| Indication | Oral | IV Dose | Volume | Freq |
|---|---|---|---|---|
| Edema | 20–80 mg | 20–40 mg | 2–4 mL | QD–BID |
| Heart Failure | 20–600 mg/day | = oral ÷ 2 | Varies | QD–BID |
| Acute Pulm. Edema | — | 40–80 mg slow IV | 4–8 mL | Repeat 1h PRN |
| Hypertension | 40 mg BID | — | — | BID |
| AKI | — | 100–200 mg | 10–20 mL | Single or CI |
| Hypercalcemia | — | 80–100 mg | 8–10 mL | Q1–2h + NS |
| Ascites | 40–160 mg + spiro | — | — | QD |
🚫
Absolute Contraindications: Anuria · Hypersensitivity to furosemide or sulfonamides · Hepatic coma with electrolyte depletion
Relative Contraindications
| Condition | Risk | Guidance |
|---|---|---|
| Hypokalemia | Severe K⁺ depletion | Correct first |
| Hyponatremia | Further Na⁺ loss | Monitor closely |
| Severe CKD | ↓ Efficacy · Ototoxicity | High-dose protocol |
| Gout | ↑ Uric acid | Monitor UA |
| Diabetes | Hyperglycemia | Monitor BG |
| Sulfa allergy | Cross-reactivity (rare) | Assess individually |
Drug–Drug Interactions
| Drug | Interaction | Severity |
|---|---|---|
| Aminoglycosides | ↑ Ototoxicity & nephrotoxicity | Major |
| Cisplatin | ↑ Nephrotoxicity & ototoxicity | Major |
| Digoxin | Hypokalemia → ↑ toxicity | Major |
| Lithium | ↓ Renal clearance → toxicity | Major |
| NSAIDs | ↓ Diuretic effect · ↑ AKI risk | Moderate |
| ACE-I / ARBs | First-dose hypotension | Moderate |
| Corticosteroids | Additive hypokalemia | Moderate |
| Warfarin | Protein binding displacement | Moderate |
| Sucralfate / Cholestyramine | ↓ Oral absorption | Minor |
Made by Dr. Ahmed Khaled|Reviewed by Dr. Mohamed Tayea
💊
Furosemide (Lasix) Clinical Suite
Evidence-based · Adult & Pediatric · PO / IV / IM · Amp: 20 mg/2 mL · 10 mg/mL
Clinical Modifiers
Loop diuretic naïve
Diuretic resistance
Hypoalbuminemia
Elderly (≥ 65 yrs)
📊 Dosing RecommendationEvidence-Based
—
🔁 Oral ↔ IV Converter
🧪 Urine Output Target
📊 Ceiling Dose Estimator
💉 Infusion Dilution Builder
⚡ Electrolyte Loss Estimator
ℹ️
Equipotent equivalents to Furosemide 40 mg PO. Starting estimates — titrate to clinical response.
Furosemide
Lasix · Reference
Equiv. PO40 mg
Equiv. IV20 mg
Bioavailability50–60%
Duration PO/IV6–8h / 2h
Torsemide
Preferred in HF
Equiv. PO10–20 mg
Equiv. IV10–20 mg
Bioavailability80–90% ✓
Duration PO/IV12–16h / 6h
Bumetanide
40× Potent
Equiv. PO1 mg
Equiv. IV1 mg
Bioavailability~80% ✓
Duration PO/IV4–6h / 2–3h
Ethacrynic Acid
Sulfa-free
Equiv. PO50 mg
Equiv. IV50 mg
Bioavailability~100% ✓
Duration PO/IV6–8h / 2h
Interactive Converter
| Drug & Route | Equiv. Dose | Note |
|---|
⚠️
Starting estimates. PO:IV = 2:1 for furosemide; ~1:1 for torsemide & bumetanide.
Key Differences
| Feature | Furosemide | Torsemide | Bumetanide | Ethacrynic |
|---|---|---|---|---|
| PO bioavailability | 50–60% | 80–90% | ~80% | ~100% |
| Potency vs furo | 1× | 2–4× | 40× | ~1× |
| PO:IV ratio | 2:1 | ~1:1 | ~1:1 | ~1:1 |
| Duration | 6–8 h | 12–16 h | 4–6 h | 6–8 h |
| Sulfonamide | Yes | Yes | Yes | No ✓ |
| HF evidence | Standard | TRANSFORM-HF ✓ | Limited | Limited |
| Ototoxicity | ++ | + | + | +++ |
ℹ️
Estimates K⁺ deficit and replacement dose. Always confirm with repeat levels. IV requires cardiac monitoring.
⚡ K⁺ Replacement PlanIndividualized
—
K⁺ Severity Reference
| Serum K⁺ | Severity | Est. Deficit | Approach |
|---|---|---|---|
| 3.5–5.0 | Normal | — | Dietary K⁺ |
| 3.0–3.4 | Mild | ~100–200 mEq | Oral KCl preferred |
| 2.5–2.9 | Moderate | ~200–400 mEq | Oral ± IV |
| <2.5 | Severe | >400 mEq | IV mandatory · Cardiac monitor |
IV KCl Rules
| Parameter | Peripheral | Central |
|---|---|---|
| Max conc. | 40 mEq/100 mL | 200 mEq/100 mL |
| Max rate | 10 mEq/h | 20–40 mEq/h (ICU) |
| Max/session | 40 mEq over 4h | 40–80 mEq |
| Monitoring | Cardiac monitor · Recheck K⁺ after each 40 mEq · Never IV push | |
ℹ️
Definition: UO <100 mL/h after 2h of IV furosemide, or <1 mL/kg/h despite adequate dosing.
1
Confirm True Resistance
Check compliance · Na <2 g/day · Rule out NSAIDs · MAP >65 mmHg · Exclude pseudo-resistance
Assess first
2
Optimize Dose
Double dose if no response after 1–2h · Switch to IV · Ensure ceiling dose reached for patient's eGFR
Dose optimization
3
Switch to Continuous Infusion
Loading 40–80 mg IV → Maintenance 10–40 mg/h → ↑ 5–10 mg/h Q2h → Target UO ≥1 mL/kg/h
Step-up
4
Add Thiazide — Sequential Nephron Blockade
Chlorothiazide 250–500 mg IV Q12h · OR Metolazone 2.5–10 mg PO 30 min before furosemide
Combination
5
Address Hypoalbuminemia
Albumin <2.5 g/dL → Albumin 25 g IV → immediately furosemide 40–80 mg IV
If applicable
6
Add Acetazolamide
500 mg IV QD · For metabolic alkalosis · ADVOR trial: benefit in decompensated HF
Advanced
7
Ultrafiltration / RRT
If all pharmacological steps fail · Severe volume overload unresponsive to diuretics
Last resort
⚠️
Monitor during combination therapy: electrolyte disturbances, prerenal AKI. BMP Q8–12h.
Baseline
BMP · Mg²⁺ · Ca²⁺ · Phosphate · UA · BG · BP · HR · Weight
1–2 h IV
UO ≥200 mL/h · BP · Response vs. resistance
Q8–12 h
K⁺ · Mg²⁺ · BUN · Creatinine · Hourly UO · Daily weight
Daily
Full BMP · Weight (0.5–1 kg/day loss) · Net fluid balance · Orthostatic BP
Weekly
BMP · Mg²⁺ · UA · K⁺ supplementation · Renal trend
Prolonged
Audiometry (ototoxicity) · Thiamine in chronic HF
Response Assessment
| Timepoint | UO | Result | Action |
|---|---|---|---|
| 1h post IV | >200 mL | Good | Continue |
| 1h post IV | 100–200 mL | Partial | ↑ dose |
| 1h post IV | <100 mL | Poor | → Resistance |
| 24h | 0.5–1 kg loss | On target | Continue |
| 24h | >1 kg loss | Over-diuresis | Reduce or hold |
Electrolyte Targets
| Electrolyte | Target | Action if Low |
|---|---|---|
| K⁺ | >3.5 mEq/L | KCl supplement · K-sparing diuretic |
| Mg²⁺ | >0.8 mmol/L | Mg sulfate IV or Mg oxide PO |
| Na⁺ | 135–145 mEq/L | Water restrict if hyponatremic |
| HCO₃⁻ | 22–26 mEq/L | Metabolic alkalosis → Acetazolamide |
🤰 Pregnancy
| FDA Category | C |
| 1st trimester | Avoid if possible |
| 2nd–3rd trimester | Lowest effective dose · Monitor fetal growth |
| Acceptable for | Pulmonary edema · NYHA III–IV · Hypertensive crisis |
| Fetal risks | Electrolyte imbalance · Possible ototoxicity · Neonatal thrombocytopenia (rare) |
🤱 Breastfeeding
| Transfer | Low amounts |
| Concern | May suppress lactation · Infant electrolyte effects |
| Recommendation | Avoid if possible · Lowest dose · Monitor infant |
👶 Neonates & Premature
| Parameter | Detail |
|---|---|
| IV / IM dose | 0.5–1 mg/kg · Max 2 mg/kg · Q12–24h |
| Oral dose | 1–4 mg/kg · Q12–24h · Bioavailability ~20% |
| Nephrocalcinosis | Risk ↑ <32 wks · Renal US Q4–8 wks |
| PDA | May worsen via ↑ renal prostaglandins |
👴 Elderly (≥ 65 years)
| Start | 20 mg/day — titrate cautiously |
| Key risks | Orthostatic hypotension · Falls · Electrolyte disturbances |
| Beers Criteria | Listed — avoid as 1st-line antihypertensive |
🫀 Cirrhosis
| Max dose | 160 mg/day · Always + spironolactone |
| Ratio | Furosemide:Spiro = 1:2.5 (40 mg : 100 mg) |
| Weight loss target | ≤0.5 kg/day (no edema) · ≤1 kg/day (with edema) |
| Avoid | Rapid diuresis · NSAIDs · High doses without spironolactone |
💉 IV Preparation & Stability — Complete Reference
📌 Ampule Specification
Concentration20 mg / 2 mL = 10 mg/mL
pH8.0–9.3 (alkaline)
AppearanceClear, colorless · Discard if discolored
StorageRoom temperature · Protect from light
🔵 IV Bolus (Intermittent)
DiluentNS (preferred) or D5W · Undiluted OK if dose ≤ 40 mg
Volume≤ 40 mg → undiluted (≤ 4 mL)
> 40 mg → dilute in 50–100 mL NS or D5W
> 40 mg → dilute in 50–100 mL NS or D5W
Final conc.≤ 10 mg/mL undiluted · Aim 1–5 mg/mL when diluting
Max rate4 mg/min = 0.4 mL/min (adult) · 0.5 mg/kg/min (peds)
Min time20 mg → ≥5 min · 40 mg → ≥10 min · 80 mg → ≥20 min · 200 mg → ≥50 min
StabilityIn NS: 24 h RT · In D5W: 24 h RT · Protect from light
🟢 IV Continuous Infusion
Loading dose40–80 mg IV bolus first, then start infusion
DiluentNS (preferred) or D5W · Do NOT use LR
VolumeDilute in 100–250 mL NS or D5W
Final conc.≤ 2 mg/mL · e.g. 200 mg in 100 mL ✓
Starting rate10–20 mg/h → ↑ 5–10 mg/h Q2h → Max 40 mg/h
StabilityIn NS: 24 h RT · In D5W: 24 h RT · Protect from light throughout
🟡 IM Injection
PreparationGive undiluted (10 mg/mL) · Max 20 mg per site
Onset~30 min · Not preferred if IV access available
StabilityUse immediately · Do not store drawn-up syringe
⚠️ pH 8–9.3 — incompatible with acidic solutions. Do NOT mix with: amiodarone, ciprofloxacin, dobutamine, dopamine, gentamicin, milrinone. Compatible with: NS, D5W, morphine, KCl in NS.
Adult Dosing by Indication
| Indication | Oral | IV Dose | Volume | Freq |
|---|---|---|---|---|
| Edema | 20–80 mg | 20–40 mg | 2–4 mL | QD–BID |
| Heart Failure | 20–600 mg/day | = oral ÷ 2 | Varies | QD–BID |
| Acute Pulm. Edema | — | 40–80 mg slow IV | 4–8 mL | Repeat 1h PRN |
| Hypertension | 40 mg BID | — | — | BID |
| AKI | — | 100–200 mg | 10–20 mL | Single or CI |
| Hypercalcemia | — | 80–100 mg | 8–10 mL | Q1–2h + NS |
| Ascites | 40–160 mg + spiro | — | — | QD |
🚫
Absolute Contraindications: Anuria · Hypersensitivity to furosemide or sulfonamides · Hepatic coma with electrolyte depletion
Relative Contraindications
| Condition | Risk | Guidance |
|---|---|---|
| Hypokalemia | Severe K⁺ depletion | Correct first |
| Hyponatremia | Further Na⁺ loss | Monitor closely |
| Severe CKD | ↓ Efficacy · Ototoxicity | High-dose protocol |
| Gout | ↑ Uric acid | Monitor UA |
| Diabetes | Hyperglycemia | Monitor BG |
| Sulfa allergy | Cross-reactivity (rare) | Assess individually |
Drug–Drug Interactions
| Drug | Interaction | Severity |
|---|---|---|
| Aminoglycosides | ↑ Ototoxicity & nephrotoxicity | Major |
| Cisplatin | ↑ Nephrotoxicity & ototoxicity | Major |
| Digoxin | Hypokalemia → ↑ toxicity | Major |
| Lithium | ↓ Renal clearance → toxicity | Major |
| NSAIDs | ↓ Diuretic effect · ↑ AKI risk | Moderate |
| ACE-I / ARBs | First-dose hypotension | Moderate |
| Corticosteroids | Additive hypokalemia | Moderate |
| Warfarin | Protein binding displacement | Moderate |
| Sucralfate / Cholestyramine | ↓ Oral absorption | Minor |
Made by Dr. Ahmed Khaled|Reviewed by Dr. Mohamed Tayea