Cardizem HCl vs. Cardizem CD: Key Differences
No, Cardizem HCl (immediate-release) and Cardizem CD (controlled delivery) are not the same—they differ fundamentally in their formulation, dosing frequency, and pharmacokinetic profiles, which directly impacts patient adherence and blood pressure control throughout the day.
Formulation Differences
Cardizem HCl refers to the immediate-release formulation of diltiazem hydrochloride that requires multiple daily doses 1.
Cardizem CD is an extended-release, once-daily formulation specifically designed for controlled delivery over 24 hours 2.
Dosing Frequency
- Immediate-release diltiazem (Cardizem HCl): Available in 30-90 mg tablets, typically dosed multiple times daily 1
- Cardizem CD: Dosed once daily with a range of 180-420 mg for hypertension and angina 2
Clinical Implications
Pharmacokinetic Profile
The once-daily CD formulation maintains more consistent blood levels over 24 hours compared to immediate-release formulations 3. Research demonstrates that:
- Diltiazem CD provides effective 24-hour blood pressure control with once-daily dosing 3
- The CD formulation significantly decreases the slope of early morning rise in diastolic and mean blood pressure, which is clinically important for cardiovascular protection 3
- Both formulations exhibit nonlinear pharmacokinetics, with apparent oral clearance decreasing 35-51% over higher dose ranges 4
Efficacy Comparison
Studies comparing once-daily CD to twice-daily SR formulations show:
- Equal efficacy: 60% of CD patients vs. 55% of SR patients achieved target diastolic BP <90 mmHg (p=0.685) 5
- Similar safety profiles: Adverse effects occurred in 37% of CD patients vs. 42.1% of SR patients, with headache and edema being most common 5
- Maintained circadian rhythm: Both formulations preserve normal blood pressure circadian patterns 3
Practical Prescribing Considerations
Starting Doses
- CD formulation: Initiate at 120-180 mg once daily, titrate to maximum 360-420 mg daily 2, 1
- Immediate-release: Requires divided dosing throughout the day 1
Patient Selection
Once-daily CD formulation is preferred for:
- Patients requiring improved medication adherence (single daily dose) 3, 5
- Those needing consistent 24-hour blood pressure control 3
- Individuals with early morning blood pressure surge 3
Common Pitfall
Do not substitute immediate-release for extended-release formulations on a milligram-per-milligram basis—the pharmacokinetic profiles differ substantially, and immediate-release requires more frequent dosing to maintain therapeutic levels 1, 4.
Monitoring Requirements
Regardless of formulation, monitor 1:
- Blood pressure and heart rate regularly
- Signs of heart failure in at-risk patients
- Liver function tests if clinically indicated
- ECG in patients with conduction system disease
Contraindications (Apply to All Formulations)
- AV block greater than first degree without pacemaker
- Decompensated systolic heart failure or severe LV dysfunction
- Wolff-Parkinson-White syndrome with atrial fibrillation/flutter
- Cardiogenic shock
- Sick sinus syndrome without pacemaker