Diltiazem: Nursing Drug Guide, Heart Block & NCLEX Review

Diltiazem is widely known as Cardizem (immediate-release tablets) and available in multiple extended-release formulations such as Cardizem CD, Cardizem LA, Tiazac, and generic diltiazem hydrochloride extended-release capsules. IV products are labeled as diltiazem hydrochloride injection (5 mg/mL). Always verify formulation on the MAR during medication reconciliation—IR, ER, and IV are not interchangeable.

Do not confuse diltiazem with dihydropyridine agents such as amlodipine or with verapamil; all are calcium channel blockers but diltiazem and verapamil slow heart rate and AV conduction, unlike amlodipine.

Per Cardizem and diltiazem hydrochloride extended-release labeling, diltiazem is used for hypertension, chronic stable angina, and angina due to coronary artery spasm. IV diltiazem is indicated for temporary ventricular rate control in atrial fibrillation or flutter (without accessory bypass tract) and for conversion of paroxysmal supraventricular tachycardia when vagal maneuvers fail.

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Diltiazem blocks L-type calcium channels in vascular smooth muscle and cardiac tissue, causing arterial vasodilation and slowing AV nodal conduction. Unlike dihydropyridines, diltiazem can reduce heart rate and prolong the PR interval—patients may perceive rhythm changes when rate slows abruptly or when an irregular heartbeat resolves after rate control. Negative inotropic effects are possible but hemodynamic impact varies with ventricular function per labeling.

IV diltiazem slows ventricular response in atrial fibrillation by blocking AV node conduction; it rarely converts AF to sinus rhythm. In Wolff-Parkinson-White syndrome, blocking the AV node can force conduction through the accessory pathway and dangerously increase ventricular rate.

Dosing depends on formulation (IR tablet, ER capsule, IV). Titrate slowly in elderly patients, hepatic impairment, and when adding nodal drugs. Verify strength and release mechanism before administration.

IV continuous infusion (AF/flutter rate control)

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Missed dose (oral): Take when remembered unless near the next dose—do not double. After a missed day, reassess pulse and blood pressure before restarting if the patient felt dizzy or had low readings at home.

Pretreatment checks

• Count apical pulse for a full minute and obtain blood pressure using proper blood pressure measurement technique
• Review rhythm strip or electrocardiogram (ECG) for PR prolongation, second- or third-degree block, or pre-excitation suggesting WPW before IV use
• Reconcile nodal drugs: digoxin, beta-blockers, ivabradine, clonidine
• Confirm formulation (IR vs ER vs IV), allergy status, and hold parameters on the MAR

Contraindications (oral and IV — labeling)

• Sick sinus syndrome without functioning ventricular pacemaker
• Second- or third-degree AV block without functioning ventricular pacemaker
• Hypotension (systolic BP <90 mmHg oral labeling; severe hypotension or cardiogenic shock for IV)
• Known diltiazem hypersensitivity
• Acute myocardial infarction with pulmonary congestion on admission chest x-ray (oral labeling)
• IV only: atrial fibrillation or flutter with accessory bypass tract (WPW or short PR syndrome)
• IV only: ventricular tachycardia; do not give IV diltiazem and IV beta-blockers together or within a few hours

Important warnings

• Cardiac conduction: May cause abnormally slow heart rates or second-/third-degree AV block; additive with beta-blockers or digitalis
• Hypotension: Symptomatic BP drops reported (3.2% symptomatic with IV in labeling)
• Heart failure: Use caution in impaired ventricular function—worsening CHF reported
• Acute hepatic injury: Rare transaminase elevations—monitor and discontinue if persistent reaction
• IV WPW risk: Life-threatening ventricular rate increase with hypotension if WPW present with AF/flutter

Important interactions

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Oral: IR tablets may be swallowed whole, crushed, or chewed per Cardizem labeling (30 mg tablets should not be split). ER capsules must be swallowed whole—do not crush or chew unless pharmacy confirms a specific formulation is safe to open.

• Take oral ER at the same time each day; avoid alcohol with ER capsules because labeling notes alcohol may increase drug release rate
• Assist patients at fall risk when orthostatic dizziness appears after dosing
• For IV: continuous ECG and frequent BP monitoring required; defibrillator and emergency equipment readily available per IV labeling
• IV bolus over 2 minutes; dedicated line preferred—many drugs are physically incompatible in the same line per IV labeling
• Refrigerate IV vials; may store at room temperature up to 1 month per current IV labeling—verify institutional policy

• Gradual blood pressure reduction on oral ER therapy without symptomatic bradycardia or hypotension
• Decreased angina episodes or improved exercise tolerance when prescribed for coronary disease
• IV bolus: measurable heart rate reduction within about 3 minutes for AF/flutter; PSVT conversion in most patients within 3 minutes of first or second bolus per labeling
• Patient remains alert with adequate perfusion—excessive slowing or hypotension is not an acceptable “response”
• Transition plan to oral antiarrhythmic or rate-control therapy before stopping prolonged IV infusion when used beyond brief control

Conduction collapse and perfusion failure can develop quickly when nodal drugs stack. Escalate immediately when hemodynamic or high-grade block cues appear.

• Heart rate below prescriber threshold or symptomatic bradycardia—hold diltiazem and notify prescriber
• New or worsening second- or third-degree AV block on monitor or ECG
• Syncope, near-fainting, or systolic BP below 90 mmHg after oral or IV dose
• After IV bolus in AF: sudden wide-complex tachycardia with hypotension—suspect WPW pathway acceleration; stop infusion and escalate emergently
• Worsening dyspnea, pulmonary congestion, or rapid weight gain suggesting heart failure decompensation

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Diltiazem overdose may cause bradycardia, hypotension, heart block, and cardiac failure. There is no specific antidote. Hemodialysis is not beneficial per labeling.

Supportive management (labeling)

• Bradycardia: Atropine 0.6–1.0 mg; isoproterenol cautiously if no response
• High-degree AV block: Treat as bradycardia; transvenous pacing for fixed block
• Cardiac failure: Inotropic agents (isoproterenol, dopamine, dobutamine) and diuretics
• Hypotension: Vasopressors such as dopamine or norepinephrine; IV fluids when appropriate
• IV calcium (chloride or gluconate) may improve response to atropine in some refractory cases—monitor for hypercalcemia
• Gastrointestinal decontamination when oral overdose and timing allow; ventilatory support as needed
• Contact local poison control or medical toxicology services per facility protocol

• Diltiazem vs diazepam / dexamethasone—verify generic name; all may appear as “D” orders on busy units
• Cardizem vs Cardene (nicardipine)—both IV antihypertensives/rate controllers but different classes and monitoring
• IR vs ER vs IV—dosing errors occur when ER capsules are given QID or IV concentration is programmed as mg/day
• Diltiazem vs amlodipine—non-dihydropyridine vs dihydropyridine; diltiazem slows HR, amlodipine often increases reflex HR
• Strength confusion—ER 120, 180, 240, 360 mg and IV 5 mg/mL require independent double-check

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Monitor

• Apical heart rate and rhythm before each oral dose; continuous telemetry during IV therapy
• Blood pressure supine and standing when symptomatic hypotension is possible
• PR interval and evidence of AV block on ECG after initiation or dose increase
• Signs of heart failure, hepatic injury, or statin myopathy when interacting drugs are present
• IV site and infusion rate in mg/h with pump double-check

Document

• Formulation, dose, time, pre-dose heart rate, and rhythm interpretation
• Hold events with prescriber notification and response
• WPW exclusion documentation before IV rate-control bolus when protocol requires
• Simvastatin dose verification and interaction checks with pharmacy

• Take ER capsules at the same time daily; swallow whole; do not double a missed dose without prescriber guidance
• Learn to count pulse and report slow heart rate, dizziness, fainting, or new irregular heartbeat sensations
• Rise slowly from sitting or lying—report lightheadedness before it leads to a fall
• Tell all clinicians about diltiazem before starting new medicines, including over-the-counter and herbal products
• Avoid alcohol with extended-release diltiazem unless prescriber advises otherwise per labeling
• Contact local poison control or toxicology services per facility guidance if too many tablets were taken

Do not give and contact the prescriber/pharmacist when:

Hold parameters may vary by institutional protocol. Follow prescriber orders, pharmacy guidance, and facility policy.

Rehearse NCLEX-style clinical judgment practice for diltiazem using a tabbed case (MAR, labs, vitals, nursing notes), then priority action, cue recognition, trend interpretation, ordered IV safety steps, WPW contraindication, and matrix urgency sorting—recognise cues → analyse → prioritise → act → evaluate outcomes.

This medication guide is written and reviewed using NurseOnShift editorial and clinical review standards.

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Educational use only. This content does not replace clinical judgment, prescriber orders, pharmacist guidance, product labeling, or institutional protocols.