Diltiazem is a non-dihydropyridine calcium channel blocker belonging to the benzothiazepine class. It has been in widespread clinical use since the 1970s, especially for its dual effect of lowering blood pressure and controlling abnormal heart rhythms. Unlike dihydropyridines (e.g., amlodipine) that act mainly on vascular smooth muscle, diltiazem exerts both vascular and cardiac effects. It works by inhibiting calcium ion influx through L-type calcium channels in cardiac and vascular tissues, which leads to relaxation of smooth muscle, vasodilation, reduced myocardial oxygen demand, and slowed atrioventricular (AV) nodal conduction.
Because of this combined profile, diltiazem is particularly useful in treating hypertension, angina pectoris (chest pain), and certain supraventricular tachyarrhythmias, such as atrial fibrillation. Its unique position among calcium channel blockers lies in its ability to reduce heart rate and cardiac workload while still producing significant vasodilation. This makes it versatile in both cardiac and vascular indications. It is available in immediate-release, extended-release, and intravenous formulations, allowing for both acute and long-term use.
Diltiazem is included in major international treatment guidelines for hypertension and atrial fibrillation rate control. It is often considered when beta-blockers are contraindicated or not tolerated. Its safety and efficacy profile has been confirmed through decades of use, though careful monitoring is required because of its potential to cause bradycardia, heart block, or interactions with other cardiovascular medications.
Patients should be instructed to take extended-release formulations at the same time each day, swallow whole, and not crush or chew. Abrupt discontinuation should be avoided, particularly in angina patients, as this can worsen symptoms.
Most adverse effects are dose-related and reversible with dose adjustment or discontinuation. Patients should be advised to report persistent swelling, unusual fatigue, or palpitations.
Patients should be educated on symptoms of bradycardia (slow pulse, dizziness, fainting) and hypotension (lightheadedness, blurred vision). Regular monitoring of blood pressure, heart rate, and ECG may be necessary during long-term therapy.
Patients should maintain an updated medication list, including over-the-counter and herbal supplements, and consult their clinician before starting any new drug.
Overdose: Presents with profound hypotension, severe bradycardia, AV block, or cardiac arrest. Supportive care includes IV fluids, vasopressors, calcium administration, and pacing if necessary.
Accidental double dose: May result in excessive dizziness, fainting, or slowed heart rate. Contact a healthcare provider immediately if symptoms occur.
Missed dose: Take as soon as remembered unless it is close to the next scheduled dose. Skip the missed dose if nearly time for the next dose. Do not double up.
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