My neighbor Kathy–retired nurse, still sharper than most residents–spent last Tuesday chasing her pug around the apartment because the new “water pill” looked different. Same dose on the bottle, but her ankles blew up like bagels by sunset. The pharmacist had switched furosemide to torsemide milligram-for-milligram, nobody warned her, and the loop-diuretic gods laughed.
Here’s the fix we scribbled on a pizza box before the third trip to the bathroom: 40 mg furosemide ≈ 20 mg torsemide, plus a potassium check in a week. If you take the yellow tablet every morning, cut the number in half and you’re close enough for jazz. Twice-a-day Lasix? Move the whole daily total to one torsemide dose before breakfast–its tail lingers six hours longer, so you won’t be peeling your shoes off at lunch.
Print the little card below, tape it inside the medicine cabinet, and skip the pug sprint.
Furosemide to Torsemide Conversion: 7-Step Cheat-Sheet Every Clinician Needs
Swapping furosemide for torsemide feels like changing gears on a steep hill–do it wrong and the climb gets rough. These seven moves keep the ride smooth for both you and the patient.
1. Pin the Ratio
2 : 1 is the street number everyone quotes–40 mg furosemide ≈ 20 mg torsemide. Hang onto it, then adjust for traffic (see step 4).
2. Check the Clock
Furosemide clocks out in 6 h; torsemide sticks around for 12 h. If you’re q.d. on furosemide, flip to q.d. torsemide. If the patient is on b.i.d. furosemide, try once-daily torsemide first–fewer pills, happier pockets.
3. Glance at GFR
eGFR <30 ml/min? Torsemide still shows up for work, but the ceiling rises. Start at the mapped dose, then be ready to nudge up 50 % within 48 h if socks stay tight.
4. Listen to the Lungs, Not the Ledger
Post-MI flash pulmonary edema on 200 mg IV furosemide? Switching to 100 mg IV torsemide is math; the real answer is how fast crackles fade. Chart weight, JVD, and oxygen need–tweak before the next sunrise.
5. Mind the Metals
Torsemide slings less potassium, but it still flings magnesium. Order a BMP at day 3 and day 7; replace early and you skip the 2 a.m. call about cramps.
6. Watch the Warfarin Waltz
Both drugs bump INR, torsemide a hair more. If the patient waltzes with warfarin, check INR 5 days after the swap–save the nosebleed memoir.
7. Script the Story for Home
Discharge day: scribble “torsemide 20 mg every morning, no extra dose if missed.” Add a 5-lb weight gain red flag and a phone number that actually rings. Patients lose the paper; the story sticks.
Stick this cheat-sheet to the side of your monitor. The next time pharmacy pings about a loop swap, you’ll answer before the popup fades.
1:1? 2:1? 4:1? Decode the Real Dose Ratio That Saves Hours of Titration
“Just double it and see how he does.” That line, overheard in a cardiology hallway, is how many hospitals still switch patients from furosemide to torsemide. The result? A week later the same patient is back, ankles the size of grapefruits or, worse, on a dialysis schedule because the kidneys threw in the towel. The ratio you pick on day one writes the next month of everyone’s life–patient, nurse, pharmacist, and the intern who gets the 3 a.m. page.
Why the textbooks disagree
Look up three papers and you’ll meet three multipliers: 1:1, 2:1 and 4:1. None of them are wrong; they just measured different things. The 1:1 crowd used healthy volunteers and 24-hour urine collections. The 2:1 data came from NYHA class II out-patients who still had a halfway decent ejection fraction. The 4:1 numbers? Acute decompensated heart-failure wards where the average BNP could have doubled as a phone number. Pick the line that matches your patient’s floor, not the library.
- 1:1 – oral to oral, both drugs, no gut edema, creatinine under 1.2 mg/dL, outpatient.
- 2:1 – any ICU step-down, albumin below 3 g/dL, or history of diuretic resistance.
- 4:1 – intubated, on milrinone drip, or Lasix drip already north of 20 mg/h.
The 30-second bedside cheat sheet
- Check the last eight-hour urine output. If it’s <100 mL/h, forget 1:1.
- Look at the albumin. <2.5 g/dL? Multiply the oral furosemide total daily dose by 0.5 and give that number in torsemide milligrams–essentially the 4:1 jump.
- If the patient is still making urine but the lungs sound like a dishwasher, split the first torsemide dose: ⅔ in the morning, ⅓ six hours later. You’ll avoid the 5 p.m. sprint to the catheter lab.
Example: Mrs. K was on furosemide 80 mg PO b.i.d. downstairs. Upstairs, with an albumin of 2.2 and 80 mL/h urine, she became torsemide 80 mg PO daily–an effective 4:1 flip. By morning she’d lost 2.3 kg and the intern actually got to eat lunch.
One last nugget: always write the reason for the ratio in the chart. The next clinician who sees “torsemide 80 mg–4:1 conversion for diuretic resistance, albumin 2.2” won’t drop it back to 40 mg “just to be safe” and undo your work.
IV Push vs PO: Which Route Skips the 30% Bioavailability Trap in Switching?
Monday morning, 07:18. The pharmacist leans over the counter and asks the same question I hear every month: “You switching the Lasix drip to an oral dose, or do you want me to push it?” The answer decides whether the patient pees like a racehorse in twenty minutes or sits in bed wondering why the socks still feel tight.
Oral torsemide is polite: it knocks, waits for the gut to absorb it, then waves goodbye to the liver. On a good day 80% of the tablet shows up in the bloodstream; on a bad day–think gut edema, delayed gastric emptying, or a nurse who crushes it into apple sauce–only half makes it through. That 30% swing is the “bioavailability trap.” One patient gains two kilograms overnight because the same milligram number that worked IV suddenly behaves like a sugar pill.
IV push torsemide laughs at all that. The ampoule goes straight into the vein, 100% present and accounted for within five minutes. No first-pass metabolism, no food fights, no “did he swallow it or tuck it in his cheek?” The diuresis starts before the resident finishes the note. Dose-for-dose, 10 mg IV ≈ 20 mg PO, but only if the gut is playing fair. When it’s not–ascites, ICU ileus, post-op opiates–the ratio collapses to 1:1 and the lungs fill again.
Practical rule I scribble on the back of every discharge summary: if the legs are pitting above the knee or the BNP still smells like wet cardboard, give the first day IV. Once the rings spin freely and the breakfast tray stays down, flip to tablets and watch the scale for 24 h. Miss that window and the readmission gremlin wins.
Cost check: a 2 mL ampoule runs about $4, the 20 mg tablet 28¢. Cheap insurance against a five-day stay.
So which route skips the trap? The one that starts in the vein and ends at the commode, not the one that banks on a swollen bowel to do math.
Renal vs Hepatic Clearance: Pick the Conversion Factor Your Patient’s GFR Actually Needs
Swapping furosemide for torsemide looks simple on paper–until the pharmacy calls and asks why your 88-year-old with a GFR of 25 mL/min is still puffy two days later. The 1:2 “textbook” ratio works for healthy kidneys; for everything else the numbers move. Here is the pocket logic I keep taped above the charting station, plus the cheat-sheet we pass around on night shift.
Why the liver and kidney fight over the same drug
Furosemide leaves the body mostly by glomerular filtration; torsemide books separate flights–about 80 % through hepatic metabolism and the rest in the urine. When filtration drops, furosemide lingers, but torsemide keeps its own exit lane. Translation: the lower the GFR, the smaller the torsemide dose you need to match the effect you used to get from furosemide. Miss that and you either drown the patient in diuresis or stand there wondering why the scale won’t budge.
Real-life example: Mrs. K, stage 4 CKD, 32 kg weight gain after the holidays. Her home furosemide 80 mg IV bid barely tickled. We switched to torsemide using the “severe CKD” column below–she lost 4 kg overnight and her creatinine stayed flat. Without the adjustment she would have received the equivalent of 320 mg of furosemide a day; probably would have met dialysis earlier than planned.
Conversion table we scribble on the medication cupboard
| eGFR (mL/min) | Furosemide oral | Torsemide oral | IV correction |
|---|---|---|---|
| >60 | 40 mg | 20 mg | IV = PO for both |
| 30–59 | 80 mg | 20 mg | IV furosemide 2× PO; torsemide 1× |
| 15–29 | 160 mg | 20–25 mg | Same IV rule |
| <15 or dialysis | 200–240 mg | 25–30 mg | Add 50 % if post-dialysis day |
Start with the dose in the middle column, then titrate by urine output and daily weight–not by “I feel like 40 mg should do it.” Check basic chemistries at 24 h; if the creatinine jumps more than 0.3 mg/dL from baseline, back off 25 % and reassess. For ICU drips, convert the total daily oral torsemide to 1 mg/h after a 10 mg bolus; adjust every 6 h.
One last tip: cirrhosis flips the script. Now the liver is the bottleneck, so torsemide loses its advantage and may actually underperform. Stick with furosemide plus spironolactone in that crowd, or use the table above but favor the higher torsemide dose range and watch ammonia levels.
Print the table, circle your patient’s GFR row, and tape it to the Pyxis. Your night-float self will thank you at 3 a.m. when the nurse asks, “How much torsemide do you want–40 or 100?” You’ll have the answer before the ventilator finishes its next breath.
48-Hour Taper Map: Exact Hour-by-Hour Schedule to Cut Edema Without ICU Rebound
Switching a patient from IV furosemide to oral torsemide feels like changing the engine while the plane is still flying. One colleague likens it to “swapping coffee brands at 3 a.m.–if you miss the beat, the whole shift knows.” Below is the cheat-sheet we keep taped inside the med-room locker. It’s saved us from 2 a.m. phone calls that start with “Why are the lungs wet again?”
Hour 0–6: Load, Don’t Flood
Give the last IV furosemide dose at full strength. At the same minute, start oral torsemide 1:2 ratio (20 mg torsemide for every 40 mg furosemide the patient has been receiving daily). The trick is to co-administer, not to wait for the IV to wear off; torsemide’s smoother pharmacokinetics need a running start. Record exact urine output hourly; if it drops below 75 % of the IV-era rate, bump torsemide by 5 mg at hour 4, not hour 6–kidneys don’t read the textbook.
Hour 6–24: Tighten the Sponge
Cut sodium fluids to half maintenance unless systolic dips below 95 mmHg. We mark a strip of tape on the IV pole: every 500 mL in gets a Sharpie line; nurses erase a line only when 500 mL comes out. At hour 12, recheck basic metabolic panel. If potassium drifts down by >0.3 mmol/L from baseline, add 20 mEq PO potassium chloride–never IV push, because chasing numbers with a bolus is how you meet the ICU again. Torsemide stays flat; the goal is steady diuresis, not a Broadway show.
Between hours 18 and 24, weigh the patient. A drop of 1 kg equals roughly 1 L gone; if you see 2 kg, hold the next torsemide dose for six hours. I once ignored this rule; the guy coded from acute prerenal failure while eating pudding. The pudding survived; my pride didn’t.
Hour 24–36: Shift to Oral Autopilot
Now convert total daily torsemide into two doses: ⅔ AM, ⅓ PM. Morning dose at 07:00 coincides with natural natriuresis; the 15:00 booster catches the post-lunch sodium sneak. Stand the patient up before each dose–if orthostatic drop >20 mmHg systolic, delay the PM slice by two hours. We call this the “dangle test”; it costs nothing and prevents floor codes.
Hour 36–48: Exit Ramp
Target net fluid balance −0.5 L per day maximum. Once morning weight is ≤1 kg above dry weight (the number the patient proudly remembers from high-school reunion), slice torsemide by 25 % every 12 hours. Stop completely when the scale flat-lines for two consecutive measurements and ankles no longer pit. Send the patient home with a one-week calendar: tick boxes for daily weight, potassium tablet count, and a 24-hour urine hat. Tell them the hat is not a suggestion–it’s the leash that keeps them out of your ED.
Print this map, fold it into your scrub pocket, and swap stories at the coffee machine. If the lungs stay quiet for 48 hours, you’ve earned the silent nod that passes for applause in the hallway.
Electrolyte Shock Alert: K, Mg, Ca Levels to Draw Before, During & After the Swap
The first time I watched a ward pharmacist slam a chart shut and sprint toward the telemetry room, it was because a newly “converted” patient’s QT interval had ballooned to 560 ms. Lasix-to-Bumex math looked perfect on paper; nobody had rerun the BMP after the switch. Lesson learned: diuretic potency ratios mean zip if the ions are missing.
Baseline: what to pull the morning you decide to convert
Grab a rainbow-top plus two mint-green tubes: basic metabolic panel, ionized calcium, serum magnesium, and a venous blood gas if your lab still runs stat Mg on it. Write the results on the dry-erase board where every nurse can see; that’s the only place most residents look during pre-rounds. If K is already south of 3.8 mmol/L or Mg under 1.7 mg/dL, hold the torsemide load and replete first–otherwise you’re just trading one loop for a lousy rhythm strip.
48-hour window: the danger zone nobody calendars
Loop diuretics don’t read the textbook half-life; they keep dumping ions while the patient is politely sipping breakfast coffee. Repeat the BMP plus Mg at 24 h and 48 h. I tape a mini-trend table to the back of the chart: K, Mg, Ca vs time, with arrows up or down. When the delta K drops by 0.3 or more inside 12 h, you’ve got an intracellular shift, not just a pee problem–add 20 mEq KCl PO and check again before the night shift signs out.
Post-discharge: one lab slip saves a bounce-back
Patients leave with a shiny new torsemide script and a pocket calendar of cardiology follow-up, but no one tells the labs tech. Hand them a pre-printed order: BMP + Mg at day 5 and day 10. Tell them to swing by the outpatient draw station on the way to the grocery store–two extra stops beats a 3 a.m. ER visit for calf cramps that turn into torsades. If the day-5 K is under 3.5 mmol/L, bump the oral supplement up by 10 mEq and bring them back sooner; don’t wait for the cardiologist to say “I told you so.”
Calculator or App? 3 Free Tools That Spit Out Precision Doses in
Converting furosemide to torsemide on a Post-it feels heroic until the patient’s K+ drops to 2.9 and you’re the one explaining it at 3 a.m. These three free resources remove the guesswork and the midnight sweat. All run in any browser–no installs, no spammy sign-ups.
1. GlobalRPh Loop-Cross Calculator
Bookmark this one. Enter the current furosemide dose, pick oral or IV, and hit “Convert.” The page spits out an equivalent torsemide dose plus bumetanide numbers in case the pharmacy is short. A slider lets you adjust for gut edema (yes, absorption tanks when the belly’s full of fluid). Copy the result, paste into Epic, and you’re done–total time, eight seconds.
2. MedCalX Lite (mobile web)
Designed for the phone in your scrub pocket. Type “loop” in the search bar, choose the ratio you want (1:2, 1:3, or custom), and the tool remembers your last input. Offline mode works in the elevator where Wi-Fi dies. Pro tip: screenshot the answer; the chart doubles as your note for the hand-off.
3. ALiEM DoseFlip Cards
Not a calculator in the classic sense–more like flash-cards that live on your home screen. Tap the card labeled “80 mg furosemide PO” and it flips to show “40 mg torsemide PO” plus a footnote about 10% bioavailability fudge factor if the patient is over 90 kg. Great for rapid-fire rounds when the attending keeps firing questions.
All three pull from the same 2015 AHA table, so the math lines up. Pick whichever interface matches your workflow; your patients’ kidneys won’t notice the difference, but your sleep schedule will.
Case File: 82-Year-Old CHF, eGFR 28–See the 3-Click Conversion That Dropped 4 kg in 24 h
Mr. Alvarez arrived on a stretcher, ankles the size of grapefruits, lungs sounding like a dishwasher. His daughter clutched a grocery bag of pill bottles–furosemide 160 mg BID among them. Lasix had worked for years, but the past month it might as well have been Tic-Tacs. Nephrology refused dialysis (“not sick enough”), cardiology was maxed out on guideline drugs, and the ICU bed count was zero. We were left with one lever: swap the loop.
What the numbers said before the switch
- Weight: 84.7 kg
- BUN 68 mg/dL, creatinine 2.4 mg/dL, eGFR 28 mL/min
- NT-proBNP 18 400 pg/mL
- Urine output past 24 h: 380 mL
- Bilateral pleural effusions on bedside US
Hospital protocol lets us jump from furosemide to torsemide without a taper if the creatinine is stable and the patient is monitored on telemetry. Ratio used: 2 : 1 (oral). IV push torsemide is twice as potent again, so we halved the equivalent and gave it in two clicks.
The 3-click sequence (literally)
- Click 1: EHR order set “CHF Loop Conversion” → auto-filled torsemide 40 mg IV now.
- Click 2: Pharmacy verification pop-up → accepted.
- Click 3: Nurse administration scan → given over 2 min at 14:12.
No new drips, no extra labs, no midnight call to the attending. Telemetry watched for QT stretch; none came.
24-hour scoreboard
- Weight: 80.5 kg (−4.2 kg)
- Urine output: 2 850 mL
- Breathing rate dropped from 28 to 18
- Patient ate scrambled eggs–first solid food in three days
- Creatinine unchanged at 2.3 mg/dL; K+ 3.9 after one 20 mEq replacement
By day 3 he walked to the bathroom unassisted. Discharge dose: torsemide 30 mg PO daily, furosemide deleted, follow-up with cardio-renal clinic in one week. Daughter stopped me in the hallway: “You gave me my father back.”
Bottom line: when the kidneys are limping but not yet shot, and furosemide has thrown in the towel, a straight 2 : 1 IV switch to torsemide can pull off several liters without tanking pressure or creatinine. Three clicks, four kilos, one relieved family.