Diltiazem Drug Profile

What is Diltiazem?

Diltiazem is a calcium channel blocker medication primarily used to treat high blood pressure and certain heart rhythm disorders. It belongs to the benzothiazepine class of calcium channel blockers, which work by relaxing blood vessels and reducing the heart’s workload. This prescription medication is available in both immediate-release and extended-release formulations for oral administration, as well as an injectable form for hospital use.

Uses

Diltiazem is FDA-approved and commonly prescribed for several cardiovascular conditions:

• Hypertension (high blood pressure): Helps lower blood pressure by relaxing arterial walls, reducing the risk of stroke, heart attack, and kidney problems
• Angina pectoris: Prevents chest pain episodes by improving blood flow to the heart muscle and reducing cardiac workload
• Atrial fibrillation and atrial flutter: Controls rapid heart rate by slowing electrical conduction through the heart’s AV node
• Paroxysmal supraventricular tachycardia: Treats episodes of abnormally fast heart rhythm originating above the ventricles
• Coronary artery spasm: Prevents arterial spasms that can reduce blood flow to the heart muscle

How it works

Diltiazem blocks calcium channels in the smooth muscle cells of blood vessels and heart tissue, preventing calcium from entering these cells. Without adequate calcium, blood vessel walls relax and widen, reducing blood pressure and improving blood flow. In the heart, this action slows electrical conduction and reduces the force of contractions, which decreases oxygen demand and helps control abnormal heart rhythms.

Side effects

Common side effects include:

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• Dizziness or lightheadedness
• Headache
• Fatigue or weakness
• Swelling of ankles, feet, or legs (peripheral edema)
• Nausea
• Constipation
• Skin rash
• Slow heart rate (bradycardia)

Serious side effects requiring immediate medical attention:

• Severe dizziness or fainting
• Chest pain or worsening angina
• Difficulty breathing or shortness of breath
• Severe swelling or rapid weight gain
• Signs of liver problems (yellowing of skin or eyes, dark urine)

Warnings and precautions

• Heart conditions: Patients with sick sinus syndrome, second or third-degree AV block, severe left ventricular dysfunction, or acute myocardial infarction with pulmonary congestion should avoid diltiazem unless a pacemaker is present
• Liver impairment: Diltiazem is extensively metabolized by the liver, requiring dose reduction in patients with hepatic dysfunction
• Pregnancy and breastfeeding: Classified as pregnancy category C; should be used only when potential benefits justify risks to the fetus. The drug passes into breast milk
• Elderly patients: May be more sensitive to the blood pressure-lowering effects and require lower starting doses
• Sudden discontinuation: Should not be stopped abruptly as this may worsen angina or cause rebound hypertension

Interactions

Diltiazem has significant interactions with many medications due to its effects on liver enzymes:

• Beta-blockers: Combined use may cause excessive slowing of heart rate and dangerous drops in blood pressure
• Digoxin: Diltiazem increases digoxin levels, potentially causing toxicity
• Statins (simvastatin, lovastatin): Increased risk of muscle damage due to elevated statin levels
• Cyclosporine: Diltiazem significantly increases cyclosporine concentrations
• Warfarin: May enhance anticoagulant effects, requiring closer monitoring
• Rifampin: Reduces diltiazem effectiveness by increasing its metabolism
• Grapefruit juice: Inhibits diltiazem metabolism, potentially increasing side effects
• CYP3A4 substrates: Diltiazem inhibits this enzyme, affecting metabolism of many drugs

Check interactions with the GMJ Interaction Checker

Dosage

Typical adult dosages vary based on the condition being treated and formulation used. For hypertension, immediate-release tablets typically start at 30-60 mg twice daily, with maintenance doses ranging from 180-360 mg per day. Extended-release formulations usually begin at 120-180 mg once daily, with maximum doses up to 480 mg daily. For angina, similar dosing ranges apply, while intravenous administration in hospital settings follows specific protocols for acute situations. Dosage should always be individualized and determined by a healthcare provider based on patient response, kidney and liver function, and concurrent medications.

Sources: FDA DailyMed drug labels (public domain), BNF, WHO Essential Medicines List. This article is for informational purposes only and does not constitute medical advice. Always consult your healthcare provider before starting or stopping any medication.

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