Robo Nurse Study Lab / Cardiac Pharmacology · Series: Antidysrhythmics 3 of 4

Antidysrhythmics set I · Overview → II · Adenosine & Beta blockers → III · CCBs & Digoxin IV · LAP drugs →

Antidysrhythmics III 🫀

The C and the D of ABCD — Calcium Channel Blockers & Digoxin

NG-060 Cardio · Pharm ADHD-friendly visual edition

ABCD = the ATRIAL rhythm drugs. Adenosine · Beta blockers · Calcium channel blockers · Digoxin. Part III takes the last two. CCBs calm the couple: HR & BP both drop. Digoxin DIGS — a deeper, stronger squeeze and a slower rate, but it does not drop the blood pressure. That one difference drives most of the test questions on this page.

📄 Simple Nursing original — opens in Drive →

🔤 ABCD = AtrialAdenosine · Beta blockers · CCBs · Digoxin — A-Fib, A-Flutter, SVT.

💊 CCBs drop 2 thingsHR ↓ and BP ↓. Dizziness on standing → slow position changes.

💛 Digoxin drops 1 thingHR ↓ only. Deeper squeeze, slower rate — NOT the BP.

🚨 Before every dose of digApical pulse 1 full minute — hold if under 60. Level over 2.0 = toxic.

🤖 Meet your study buddy — Pulse, the cardio rescuer

🧠 “Say your ABCDs to the atria.” If the rhythm problem is above the ventricles — A-Fib, A-Flutter, SVT — reach for an ABCD drug. If the rhythm starts with a V, you need the LAP drugs instead → Antidysrhythmics IV, NG-062.

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WHAT THEY DO

STEP 1 · MECHANISM

One blocks calcium so the heart stops squeezing so hard and so fast — the other adds calcium inside the cell so it squeezes harder but beats slower.

🧱 Calcium channel blockers — block calcium, calm the heart

Calcium CONTRACTS muscle. So when you block calcium from entering the cardiac and vascular smooth-muscle cells, you get the exact opposite: less squeeze, slower conduction, wider vessels.

🧠 “CCBs lower the COUPLE.” A couple is two — and CCBs drop two heart vitals: HR and BP. Digoxin is single: it drops HR only.

💊 Know these two names cold

Verapamil — heart-selective, hits rate hardest
Diltiazem — heart + vessels, the classic A-Fib rate-control drip
Amlodipine — vessel-selective, mostly a blood pressure drug (the dizziness one)

Given for: Hypertension · Tachycardia · SVT · A-Fib · A-Flutter.

🧠 “Very Dill Amazing” — Verapamil, Diltiazem, Amlodipine. The first two slow the beat; the last one softens the pressure. Full class page: NG-195.

🎯 Intended effect = the ventricular rate comes DOWN

The classic stem: “A client in A-Fib is started on diltiazem. Which finding shows the intended effect?”

Answer: Ventricular rate decreased from 160 to the 70s.

Notice what the answer is not: the A-Fib did not convert. Rate control ≠ rhythm conversion. The atria are still fibrillating — you just slowed how many of those impulses get through the AV node.

🧠 “Slow the gate, not the storm.” The atrial storm keeps raging; the AV gate just lets fewer beats through.

🚪 Where they work: the AV node is the gate

🧠 “One gate, four keys.” Adenosine, Beta blockers, CCBs and Digoxin all throttle the AV node. Give two at once and the gate can slam shut — bradycardia and heart block.

💛 Digoxin — D is for DEEP contraction

Digoxin DIGS for a deeper, more forceful contraction and slows the heart rate — so cardiac output goes up while the heart works less. That is why it treats A-Fib and heart failure with the same pill.

🧠 “DIG DEEP, beat SLOW, pressure STAYS.” Three words, three answers. The trap answer on every dig question is “teach slow position changes” — that belongs to the CCBs, not dig.

⚖️ CCBs vs Digoxin — the confusion table

	🧱 Calcium channel blockers	💛 Digoxin
Examples	Verapamil · Diltiazem · Amlodipine	Digoxin (cardiac glycoside)
Heart rate	↓ Down	↓ Down
Blood pressure	↓ Down — vessels relax	Unchanged
Contractility	↓ or neutral	↑ Up — deeper squeeze
Signature side effect	Orthostatic hypotension · dizziness on standing	Toxicity — anorexia, N/V, vision changes
Signature teaching	Slow position changes	Apical pulse 1 min, hold if <60
Key lab	BP & HR trend	Potassium + digoxin level + creatinine
Also used for	HTN, SVT, A-Fib, A-Flutter, tachycardia	A-Fib & heart failure

🧠 Two drugs, one question: “which vital did the drug change?” Two vitals moved = CCB. One vital moved = digoxin.

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WATCH FOR

STEP 2 · ADVERSE EFFECTS

CCBs make them dizzy on the way up. Digoxin makes them nauseated, bradycardic and unable to read the newspaper.

😵‍💫 CCB #1 adverse effect: orthostatic hypotension

Vessels relaxed + rate slowed = the blood pressure cannot catch up when they stand. Dizziness on standing is the priority adverse effect to watch for — because the next step is a fall.

🧠 “Verapamil = Very a-pillow… get up slow.” Every CCB question about teaching lands on the same answer: change positions slowly.

🚨 Digoxin toxicity — the first signs are in the GUT and the EYES

🥄 Anorexia — usually the very first sign
🤢 Nausea & vomiting
👁️ Vision changes — “can't read my book,” blurred, yellow-green halos
😵 Dizziness & lightheadedness — report it
🐢 Bradycardia — the rate keeps sliding down

Do not give the next dose if toxicity signs are present — hold it and call the provider.

🧠 “A-N-V-D” = Anorexia · Nausea · Vision · Dizzy. Or picture the client pushing away a dinner tray because the food looks yellow-green. That's dig toxicity in one image.

🧪 Digoxin level: the narrow window

<0.5 sub-therapeutic

0.5 – 2.0 ng/mL therapeutic

>2.0 ng/mL TOXIC 🚨

Max safe = 2.0 ng/mL. Under 2.0 is safe; over 2.0 is toxic. In heart failure many providers aim lower — around 0.5–0.8 ng/mL — so always read the ordered target.

Antidote: digoxin immune Fab (DigiFab) for severe toxicity.

🧠 “Two is too much.” 2.0 is the ceiling — one number, one hand of two fingers, easy to picture at the bedside.

🧪 The lab that causes the toxicity: potassium under 3.5

Digoxin and potassium compete for the same site on the sodium-potassium pump. Low potassium = more room for digoxin to bind = toxicity at a “normal” level. This is why the diuretic on the same MAR is so dangerous.

So the NCLEX answer to “client on digoxin can't read her book — what lab do you check?” is the potassium (and the digoxin level). Vision change = toxicity, and low K is what pushed them there.

🧠 “Low K = high dig.” They see-saw. Any potassium-wasting diuretic (furosemide, HCTZ) on the same med list is a red flag — anticipate a potassium supplement.

🧪 Don't forget the kidneys — creatinine over 1.3

Digoxin is cleared by the kidneys. Bad kidneys = the drug stacks up = toxicity, even on the same old dose.

🧪 Creatinine — adult normal roughly 0.6–1.2 mg/dL; over 1.3 = worrying
👵 Older adults — lower muscle mass and lower GFR = higher risk
💧 Dehydration concentrates the drug

🧠 “Kidneys keep the key.” If the kidneys quit, the digoxin never leaves — same dose, rising level.

⚠️ Never stack the gate-blockers casually

A client already on a beta blocker who gets IV verapamil or diltiazem can drop into profound bradycardia, heart block or hypotension.

Hold the dose and clarify the order if the HR is already under 60 or the systolic BP is under 90.

🧠 “Two brakes, one hill.” Two AV-node brakes on the same patient is how a rate-control order becomes a rapid response.

🧑‍🏫

TEACH

STEP 3 · SAFETY & TEACHING

Three sentences the client has to be able to repeat back — and the three test questions built from them.

✅ Before EVERY dose of digoxin — the ABCD check

Apical pulse for a FULL minute — stethoscope at the apex, not the wrist. Hold if under 60 in an adult and notify the provider.

Baseline symptoms — ask about appetite, nausea, vision. “Any trouble reading today?”

Check the labs — potassium 3.5–5.0, digoxin level under 2.0, creatinine.

Document the rate you counted before you give it. If you didn't chart it, you didn't check it.

🧠 “Apical for a minute, hold at sixty.” Say it as a rhyme before you ever pick up the pill cup. Deeper dive: NG-208 Digoxin.

🥬 If they're also on warfarin for A-Fib

🧪 Monitor the INR
💉 Antidote = vitamin K
🥗 Consistent — not zero — green leafy vegetables. Keep vitamin K intake steady, don't swing it.

🧠 “Warfarin wants routine.” The diet rule is consistency, and the classic wrong answer is “avoid all green vegetables.”

🗣️ Say it in the client's words

CCB: “Sit on the edge of the bed and count to ten before you stand.”
Digoxin: “Take your pulse for a full minute every morning. If it's under 60, call before you take the pill.”
Digoxin: “If food stops tasting right, or the print looks blurry or yellow, call us.”
Both: “Don't stop it on your own, and bring the bottle to every visit.”

🧠 Teach-back is the win condition: if she can say it back, it's charted as understood.

⭐ The three questions this infographic is built to answer

Question stem	Answer
Intended effect for diltiazem?	Ventricular rate decreased from 160 to the 70s
Priority adverse effect for amlodipine?	Dizziness (orthostatic hypotension)
Most important teaching for verapamil?	Slow position changes
Client on digoxin can't read her book — key lab?	Potassium (with the digoxin level) — low K drives toxicity

🧠 “Rate down, dizzy up, stand slow, check the K.” Four beats, four answers — chant it once and this whole page is stored.

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QUICK RECALL

SAY IT OUT LOUD

🧱 CCB = 2 vitalsHR ↓ and BP ↓ → dizziness → slow position changes.

💛 Dig = 1 vitalHR ↓ only. Deeper squeeze. BP untouched.

👁️ Blurry + yellow= digoxin toxicity. Check level (>2.0) and potassium (<3.5).

🩺 Apical <60 = HOLDOne full minute, every dose, then chart it.

🎯 Cover & check — 6 rapid-fire questions

Q1: What does ABCD stand for, and which rhythms does it treat?

Adenosine · Beta blockers · Calcium channel blockers · Digoxin — the ATRIAL rhythm drugs: A-Fib, A-Flutter and SVT (plus rate/BP control).

Q2: A client on diltiazem for A-Fib. Which finding shows the drug worked?

Ventricular rate dropped from 160 to the 70s. Rate control — the rhythm itself is still A-Fib.

Q3: Which two vital signs do CCBs lower, and which one does digoxin leave alone?

CCBs lower HR and BP. Digoxin lowers HR only — blood pressure is unchanged, so slow-position-change teaching is not the digoxin answer.

Q4: Apical pulse before digoxin is 54. Now what?

HOLD the dose and notify the provider. Count apically for a full minute; hold if under 60 in an adult, and document the rate.

Q5: Name the first signs of digoxin toxicity in order.

Anorexia first, then nausea/vomiting, then vision changes (blurred, yellow-green halos, “can't read”). Also dizziness and worsening bradycardia. Level above 2.0 ng/mL is toxic; antidote is digoxin immune Fab.

Q6: Which electrolyte makes digoxin toxicity more likely, and at what value?

Potassium — below 3.5 mEq/L. Low potassium frees up binding sites so digoxin acts stronger. Watch anyone on a potassium-wasting diuretic.