What is the recommended dosage of diltiazem (calcium channel blocker) for a 71-year-old patient with potential hypotension (low blood pressure) and impaired renal (kidney) or hepatic (liver) function?

Diltiazem Dosing in a 71-Year-Old Patient

Start with diltiazem 120 mg once daily using an extended-release formulation, and titrate cautiously over several weeks while closely monitoring blood pressure and heart rate, particularly given the increased risk of hypotension in elderly patients. 1, 2

Initial Dosing Strategy

• Begin with 120 mg once daily of an extended-release formulation (such as Cardizem CD), which represents the minimum effective starting dose for elderly patients 1, 3
• The 120 mg starting dose is specifically recommended for elderly patients (age 65-85 years) to minimize adverse effects while maintaining efficacy 2
• Extended-release formulations provide consistent 24-hour blood pressure control and allow once-daily dosing, improving adherence 1, 4

Titration and Dose Adjustment

• Titrate gradually at 1-2 week intervals based on blood pressure response and tolerability 1, 2
• The therapeutic range extends from 120-360 mg daily, though elderly patients often respond optimally to lower doses 1, 3
• For elderly patients specifically, 180-200 mg once daily is often the optimal dose, with one study demonstrating that 180 mg/day provided adequate angina control with fewer adverse effects than higher doses in patients aged 71-82 years 5
• If blood pressure control is inadequate at 200 mg, the dose can be increased to 300 mg once daily 2
• Maximum dose is 360 mg daily, though doses above 240 mg show incremental but modest additional benefit 6, 4

Critical Monitoring Requirements

Blood Pressure and Heart Rate:

• Monitor blood pressure and heart rate at each dose adjustment (every 1-2 weeks initially) 1
• Reassess patients 1 month after initiation or dose changes 1
• Hypotension is the most common adverse effect, particularly in elderly patients, and requires careful monitoring 1, 7

Cardiac Monitoring:

• Obtain baseline ECG and monitor for conduction abnormalities, especially if the patient has any pre-existing conduction system disease 1
• Watch for bradycardia, which may be dose-limiting 1

Liver Function:

• Check liver function tests if clinically indicated, as diltiazem is hepatically metabolized 1

Special Considerations for Elderly Patients

Renal and Hepatic Impairment:

• If renal or hepatic dysfunction is present, titration must be carried out with particular caution, as no specific dosing guidelines exist for these populations 3
• Start at the lowest dose (120 mg) and increase more slowly than in younger patients 3

Common Adverse Effects in the Elderly:

• Constipation is particularly problematic in elderly patients and may be severe enough to require discontinuation 5
• Peripheral edema occurs in a dose-dependent manner and is more common in women; consider adding a diuretic if this develops 1
• Dizziness and lightheadedness from hypotension 2, 7

Absolute Contraindications

Do not use diltiazem if the patient has: 1, 3

• Second or third-degree AV block without a functioning pacemaker
• Sick sinus syndrome without a pacemaker
• Decompensated systolic heart failure or severe left ventricular dysfunction
• Cardiogenic shock
• Wolff-Parkinson-White syndrome with atrial fibrillation/flutter
• Hypotension (systolic BP <90 mmHg)

Drug Interactions to Avoid

• Do not combine with beta-blockers unless absolutely necessary, as this significantly increases the risk of bradycardia, heart block, and heart failure 1
• Exercise caution with other CYP3A4 substrates and inhibitors (diltiazem is both a CYP3A4 substrate and moderate inhibitor), including cyclosporine, simvastatin, and certain anticoagulants 1
• Avoid concurrent use with medications that affect SA/AV nodal conduction 1

Practical Dosing Algorithm

1. Start: 120 mg once daily (extended-release formulation) 1, 2
2. Week 2-4: Assess response - if blood pressure not at goal and no adverse effects, increase to 180-200 mg once daily 2, 5
3. Week 6-8: Reassess - if still inadequate control, increase to 240-300 mg once daily 2, 6
4. Maximum: 360 mg once daily if needed, though elderly patients rarely require this dose 1, 3

Common Pitfalls to Avoid

• Do not split, crush, or attempt to "half" extended-release formulations - they must be swallowed whole to maintain their controlled-release properties 1
• Do not use immediate-release formulations once daily - these require 3-4 times daily dosing 3
• Do not escalate doses too rapidly in elderly patients - this increases the risk of hypotension and other adverse effects 1, 5
• Do not assume diltiazem requires tapering when discontinuing - unlike beta-blockers, there is no significant withdrawal syndrome, and the medication can be stopped abruptly if needed 8