CC Pharm | Diltiazem

Diltiazem (Cardizem) Clinical Summary 1. Action & Class: Benzothiazepine Class IV anti-arrhythmic/anti-anginal. Inhibits calcium influx across myocardial and vascular smooth muscle membranes. This slows AV conduction (prolonging the PR interval), decreases heart rate, and dilates coronary and systemic arteries, reducing afterload and blood pressure. It has fewer negative inotropic effects than verapamil. 2. Therapeutic Uses: Hypertension, stable/variant (Prinzmetal's) angina, and ventricular rate control in atrial fibrillation (AFib), atrial flutter, or PSVT. 3. Administration & Dosages: IV Push: Undiluted, over 2 minutes (0.25 mg/kg bolus; can repeat at 0.35 mg/kg in 15 minutes if needed). Continuous IV: 1 mg/mL dilution, starting at 10 mg/hour; titrate to a maximum of 15 mg/hour (duration >24 hours is not recommended). Oral: IR tablets (30–90 mg, 3–4 times daily). ER formulations (12- or 24-hour) range 120–360 mg/day (maximum 360–540 mg/day depending on formulation). Do not crush or chew ER formulations. 4. Complications & Adverse Effects: Severe: Bradycardia, high-degree AV block, asystole, heart failure, and life-threatening dermatologic reactions like Stevens-Johnson syndrome (SJS) or toxic epidermal necrolysis (TEN). Common: Peripheral edema (up to 15%), hypotension (4.3%), constipation (3.6%), headache (8.9%), and dizziness (10%). 5. Contraindications & Interactions: Contraindications: Severe heart failure, sick sinus syndrome, 2nd/3rd-degree AV block (without a functioning pacemaker), cardiogenic shock risk, or atrial arrhythmias presenting with pre-excitation (e.g., Wolff-Parkinson-White). Interactions: CYP3A4 substrate and inhibitor; can significantly raise levels of co-administered CYP3A4 substrates. Avoid/limit grapefruit juice (increases drug half-life). Concurrent beta-blockers severely compound the risk of AV block. 6. Nursing Interventions: Monitoring: Monitor ECG (PR interval) and blood pressure/heart rate continuously during IV therapy. Hold Parameters: Hold the dose and immediately notify the provider for severe bradycardia, new-onset heart block, or profound hypotension. Organ Function: Reduce dosage in hepatic impairment (increases half-life and bioavailability); no renal adjustments are required. 7. Client Education: Never split, crush, or chew ER formulations. However, Tiazac capsules can be opened and sprinkled on cool, non-hot applesauce. Change positions slowly to prevent orthostatic hypotension and syncope. Report severe rashes, swelling in lower extremities, or extreme fatigue immediately.