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Nursing Field Notes / Renal + Fluid · Pharmacology

Potassium-Sparing 🍌

Spironolactone (Aldactone) · eplerenone (Inspra) · triamterene · amiloride

NG-181 Renal + Fluid ADHD-friendly visual edition

The weakest diuretic — and the only one that doesn’t steal potassium. It works at the very end of the nephron: block aldosterone (or the sodium channel itself) and sodium + water leave while potassium stays in the blood. That is the benefit and the danger in one sentence: HYPERkalemia.

📄 Simple Nursing original — opens in Drive →

🍌 Site = late DCT + collecting ductBlocks aldosterone / the Na⁺ channel. Na⁺ + H₂O out, K⁺ stays in.
🚨 HYPERkalemia is the riskHold & report K⁺ over 5.0 mEq/L — peaked T waves.
🧂 NO salt substitutesThey are potassium chloride. No K⁺ supplements, no high-K⁺ foods.
🧍 Spironolactone = gynecomastiaIt blocks sex-hormone receptors too. Eplerenone if that’s a problem.
⚙️

WHAT IT DOES

STEP 1 · THE MECHANISM

Last stop on the nephron — the only segment where sodium and potassium are traded for each other.

🗺️ Where it works: the late DCT & collecting duct

Source wording: “Potassium-sparing diuretics reduce the excretion of potassium, block the reabsorption of sodium into the kidney, and thereby increase sodium and H₂O in the urine and reduce excretion of K⁺.”

THE NEPHRON — one tubule, four drug sites Filtrate runs left → right. Whatever the drug blocks stays in the tube and leaves as urine. blood in → Glomerulus + Bowman’s capsule filtration starts here proximal tubule (PCT) thin descending limb ↓ thick ASCENDING limb ↑ loop of Henle early DCT distal convoluted tubule → late DCT collecting duct principal cells — aldosterone acts here ↓ urine → bladder 1 2 3 4 ✕ ⛔ Na⁺/K⁺ SWAP OFF 1 OSMOTIC · mannitol Proximal tubule + thin descending limb — raises the osmolality of the filtrate so water cannot be reabsorbed 2 LOOP · furosemide, bumetanide, torsemide Thick ASCENDING limb — blocks the Na⁺/K⁺/2Cl⁻ (NKCC2) pump. Strongest class; wastes K⁺ AND Ca²⁺ 3 THIAZIDE · hydrochlorothiazide, metolazone EARLY distal convoluted tubule — blocks the Na⁺/Cl⁻ (NCC) pump. Wastes K⁺ but KEEPS Ca²⁺ 4 POTASSIUM-SPARING · spironolactone, triamterene ◀ YOU ARE HERE LATE DCT + collecting duct — blocks aldosterone / the Na⁺ channel, so K⁺ is NOT dumped
🧠 Last stop = last chance. By the time filtrate gets here only a few percent of the sodium is left — which is exactly why this class is the weakest diuretic and is usually a partner drug, not a solo act.

🔬 Zoom in: two different drugs, one canceled trade

INSIDE THE COLLECTING DUCT — the sodium-for-potassium trade Normally the body swaps Na⁺ back IN and throws K⁺ OUT. These drugs cancel the swap. TUBULE LUMEN the future urine PRINCIPAL CELL BLOOD Na⁺ channel ENaC Na⁺ K⁺ ✕ K⁺ does NOT get dumped ALDO receptor tells the cell to build more Na⁺ channels & pumps aldosterone the salt-saving hormone SPIRO ① spironolactone / eplerenone — block the HORMONE’s receptor ② triamterene / amiloride — plug the CHANNEL itself. Either way: Na⁺ out, K⁺ stays. TRIAM ② triamterene / amiloride block the CHANNEL directly — no hormone LEAVES IN THE URINE Na⁺ + H₂O 💧 only a mild diuresis K⁺ STAYS IN THE BLOOD → HYPERkalemia risk the point — and the danger
🧠 “Spiro fights the hormone, Triam plugs the hole.” Spironolactone & eplerenone sit on the aldosterone receptor; triamterene & amiloride plug the sodium channel. Either way: Na⁺ out, K⁺ stays.

💊 Two families — know which one causes the breast tissue

FamilyDrugsHow it works & what’s different
Aldosterone antagonistsSpironolactone (Aldactone)
Eplerenone (Inspra)		 Block the aldosterone (mineralocorticoid) receptor. Spironolactone also blocks sex-hormone receptors → gynecomastia, hirsutism. Takes days for the full effect. Proven survival benefit in heart failure.
Sodium-channel blockersTriamterene (Dyrenium)
Amiloride (Midamor)		 Plug the ENaC sodium channel directly — no hormone involved, so no hormone side effects. Often combined with HCTZ in one tablet.
🧠 “-one blocks the hormone.” Spironolactone and eplerenone end in -one, like aldosterone. The -terene / -oride pair just plugs the pipe.

🎯 Why do we give it? “Reason”

  • 🩺 Hypertension — often with other antihypertensives
  • 🍌 To protect potassium when a loop or thiazide is dumping it
  • ❤️ Heart failure — spironolactone improves survival in HF with reduced EF
  • 🩸 To reduce edema — the drug of choice in cirrhosis with ascites, where aldosterone is high
  • 🧪 Hyperaldosteronism
🧠 High aldosterone states = spironolactone’s home turf: heart failure, cirrhosis/ascites, hyperaldosteronism. Fight the hormone that is causing the retention.

💊 The drug — generic, trade, safe dose, route SOURCE

GenericTradeDose · route
SpironolactoneAldactone25–400 mg/day as a single dose · PO

Also on the shelf: eplerenone (Inspra), triamterene (Dyrenium), amiloride (Midamor), and fixed combinations of triamterene + HCTZ.

🧠 Give it in the MORNING as a single dose — same rule as every diuretic. And warn her: spironolactone takes several days to show its full effect, so don’t expect a flood on day one.
🚨

WATCH FOR

STEP 2 · ADVERSE EFFECTS

One number owns this page: potassium over 5.0.

🧪 The lab picture — the ONE diuretic that raises K⁺

WHAT A POTASSIUM-SPARING DIURETIC DOES TO THE LABS Standard adult reference ranges — your facility’s lab sheet is the final word. Potassium K⁺ normal 3.5–5.0 mEq/L NORMAL LOW ↑ hyperkalemia risk Sodium Na⁺ normal 135–145 mEq/L NORMAL HIGH ↓ excreted with water Chloride Cl⁻ normal 98–106 mEq/L NORMAL HIGH ↓ mild loss Magnesium Mg²⁺ normal 1.5–2.5 mEq/L NORMAL LOW HIGH SPARED too BUN / creatinine BUN 10–20 mg/dL · creat 0.6–1.2 NORMAL LOW ↑ if kidneys decline
↑ K⁺ — the danger↓ Na⁺↓ Cl⁻ Mg²⁺ spared↑ BUN/creat if dry
🚩 Source note: the original card’s shared F & E list contains both “hyperkalemia” and “hypokalemia.” For this class, only one is true: potassium-sparing diuretics cause HYPERkalemia. Hypokalemia belongs to the loop and thiazide pages.
🧠 Every other diuretic dumps K⁺. This one banks it. If a question mixes classes, ask first: “which way is the potassium moving?”

🚨 Hyperkalemia — the emergency this drug creates

POTASSIUM CLIMBING — read it on the monitor Normal K⁺ 3.5–5.0 mEq/L. Every step right is a step closer to cardiac arrest. 3.5–5.0 NORMAL normal P-QRS-T 5.1–6.0 HOLD & REPORT tall PEAKED T waves 6.1–7.0 EMERGENCY WIDE QRS · flat P · slow > 7.0 ARREST SINE WAVE → asystole Also feel for it: muscle weakness · tingling · bradycardia · irregular pulse · diarrhea HOLD the dose and report a serum K⁺ over 5.0 mEq/L.
🧠 “Peaked T = peaked K.” The T wave stands up and points at the answer. Tall, tight, tented T waves = potassium is too high.

❌ Never add more potassium

THREE WAYS EXTRA POTASSIUM SNEAKS IN — block all three KCl SALT SUBSTITUTE it IS potassium chloride K⁺ K⁺ SUPPLEMENTS and ACE inhibitors / ARBs 🍌 🥑 🥔 HIGH-K⁺ FOODS banana · avocado · potato… The drug already keeps her potassium — adding more is how the heart stops.

No potassium supplements. No salt substitutes. No “low-sodium salt.”

🧠 The shaker is the trap. “Salt substitute” sounds heart-healthy and is literally potassium chloride — the single most missed teaching point on this drug.

🧍 Spironolactone’s hormone effects

SPIRONOLACTONE ALSO BLOCKS SEX-HORMONE RECEPTORS 🧍 Gynecomastia breast enlargement & tenderness in men — the #1 reason it gets stopped 🧔 Hirsutism · deepened voice unwanted hair growth in women 🗓️ Menstrual irregularity · impotence · ↓ libido EPLERENONE (Inspra) = same job, far fewer hormone effects.
🧠 “Spirono-LACT-one” — the LACT in the middle is your reminder: breast tissue. Gynecomastia in men, hirsutism and irregular periods in women.

⚠️ Adverse effects by system SOURCE LIST

NeuroDizziness, headache, lightheadedness, weakness, fatigue
CVOrthostatic hypotension, arrhythmias from ↑K⁺
GUElectrolyte imbalances
GIAnorexia, nausea, vomiting, diarrhea / cramping
DermRash, photosensitivity
EndoGynecomastia, hirsutism, menstrual irregularity, impotence
F & EHYPERkalemia, hyponatremia, dehydration
MSArthralgia, muscle cramps, myalgia
🧠 Confusing overlap: muscle weakness and cramps show up in BOTH high and low potassium. Don’t guess — get the level.

❌ Contraindications & cautions SOURCE

  • 🚫 Hyperkalemia — the absolute one
  • 🚫 Hypersensitivity
  • 🚫 Severe kidney or liver dysfunction
  • 🚫 Anuria
  • 🚫 Addison’s disease — already low aldosterone, already high K⁺
  • ⚠️ Caution: diabetes & older adults — both retain potassium more easily
🧠 Addison’s + a potassium-sparing diuretic = two hits of the same problem.

🧠 NCLEX traps that live on this drug

The stem says…The answer is…
Client on spironolactone uses a salt substituteSTOP — it is KCl → hyperkalemia
K⁺ comes back 5.8 mEq/LHold the dose and notify the HCP
Peaked T waves on the monitorHyperkalemia — check the level, priority
Client also takes an ACE inhibitor or ARBBoth raise K⁺ — monitor closely
Male client reports breast tendernessSpironolactone side effect — report; eplerenone may be substituted
Which foods to limit?Banana, avocado, spinach, potato, salmon, beans, coconut water
“Which diuretic raises potassium?”Potassium-sparing — the only one
🧠 K.E.E.P. — K⁺ climbs · ECG peaked T · Endocrine effects · Potassium sources banned.
🗣️

TEACH

STEP 3 · NURSING MANAGEMENT

Same diuretic teaching as the other classes — with the potassium instruction flipped upside down.

✅ The teaching ladder

1
🍌 AVOID high-potassium foods, potassium supplements and salt substitutes — the exact opposite of the loop/thiazide instruction.
2
🌅 Take it early in the morning, as a single daily dose.
3
⚖️ Weigh yourself daily; keep intake & output. 1 kg = 1 L.
4
🚫 Do not stop the drug abruptly unless you speak with the HCP.
5
🍽️ GI upset? Take it with food or milk. Do not reduce fluid intake on your own.
6
🍺 Avoid alcohol and non-prescription drugs — especially NSAIDs.
🧠 “Spare the K, skip the shaker.” One sentence covers the food list, the supplement and the salt substitute.

🍌 Foods to AVOID SOURCE LIST

🥑Avocado
🎃Acorn squash
🥬Spinach
🍠Sweet potato
🐟Salmonwild-caught
🍑Dried apricots
🫛Pomegranate
🥥Coconut water
🥫White beans
🍌Banana
🧠 Same tray, opposite order. On a loop diuretic she eats this plate; on spironolactone she pushes it away. That flip is worth two exam questions.

📞 Notify the HCP for… SOURCE

  • 💪 Muscle cramps or weakness
  • 🧠 Numbness or tingling (hyperkalemia)
  • 😵 Dizziness, restlessness
  • 💩 Diarrhea, GI distress
  • 💓 Irregular or slow pulse, palpitations
  • 🧍 Breast tenderness or enlargement
🧠 Tingling + weak + slow pulse = think potassium too HIGH on this drug — not too low.

👩‍⚕️ Nurse’s checklist

  • 🧪 Serum K⁺ before dosing and routinely — the single most important lab
  • 📈 Monitor BP and pulse frequently
  • 📊 Strict I&O + daily weight
  • 💓 Cardiac monitor / ECG if the K⁺ is climbing
  • 🧪 Also follow Na⁺, BUN, creatinine
  • 💊 Review the whole med list for ACE inhibitors, ARBs, K⁺ supplements, NSAIDs
🧠 “Check the K⁺ before you pass it.” Make it a reflex with this class the way apical pulse is a reflex with digoxin.

🔄 Interactions SOURCE

With…What happens
ACE inhibitors / ARBsIncreased risk of hyperkalemia
Potassium supplements & salt substitutesIncreased risk of hyperkalemia
NSAIDsDecreased diuretic effect + higher K⁺
AnticoagulantsDecreased diuretic effect
DigoxinSpironolactone can raise digoxin levels — monitor
LithiumLithium retained → toxicity risk
🧠 “ACE + spiro = ↑K⁺.” Two of the most common heart-failure drugs in the same client. Someone has to watch that potassium — it is you.
⚡

QUICK RECALL

SAY IT OUT LOUD
🍌 Late DCT + collecting ductAldosterone / Na⁺ channel blocked · weakest class
🚨 K⁺ over 5.0Hold · report · peaked T waves
🧂 Salt substitute = KClNo supplements · no high-K⁺ foods · watch ACE/ARBs
🧍 GynecomastiaSpironolactone only — swap to eplerenone

🧠 The one mnemonic for this page: K · E · E · P — this drug KEEPs potassium, so you add none.

  • K — K⁺ climbs: hold & report over 5.0 mEq/L
  • E — ECG: tall peaked T waves → wide QRS → sine wave
  • E — Endocrine: gynecomastia, hirsutism, menstrual changes (spironolactone)
  • P — Potassium sources banned: supplements, salt substitutes, high-K⁺ foods, ACE/ARBs
🎯 Cover & check — 6 rapid-fire questions
Q1: Where do potassium-sparing diuretics act?
The late distal convoluted tubule and collecting duct — on the principal cell, by blocking aldosterone (spironolactone, eplerenone) or the sodium channel itself (triamterene, amiloride).
Q2: Which electrolyte does this class spare, and what is the danger?
Potassium — it stays in the blood. The danger is HYPERkalemia: hold the dose and report a K⁺ over 5.0 mEq/L.
Q3: Why is a salt substitute dangerous here?
Salt substitutes are potassium chloride — they add exactly the electrolyte the drug is already saving.
Q4: What is the first ECG change of a rising potassium?
Tall, peaked (tented) T waves — later a flattened P wave, widened QRS, then a sine wave and arrest.
Q5: A male client on spironolactone reports enlarged, tender breasts. What is happening?
Gynecomastia — spironolactone blocks sex-hormone receptors as well as aldosterone. Report it; eplerenone has far fewer hormone effects.
Q6: Why is spironolactone the diuretic of choice in cirrhosis with ascites?
Those clients have high aldosterone levels driving sodium and water retention — this drug blocks aldosterone directly.