Onset of Action for Cardizem CR (Diltiazem Controlled-Release)
Cardizem CR begins lowering blood pressure within 2 hours of administration, with peak effects occurring at approximately 4-5 hours, and sustained action maintained throughout the 12-hour dosing interval. 1
Blood Pressure Lowering Timeline
- Initial onset occurs within 2 hours of the first dose, with measurable reductions in both systolic and diastolic blood pressure documented at this timepoint 1
- Peak antihypertensive effect is achieved at 4-5 hours post-dose, with the nadir blood pressure typically occurring around hour 5 (mean reduction from 154/101 mmHg at baseline to 139/84 mmHg at peak effect) 1
- Sustained effect persists through 12 hours, maintaining significant blood pressure reduction at the end of the dosing interval (149/91 mmHg at hour 12) 1
The controlled-release formulation demonstrates a longer time to maximum concentration (tmax of 4.4 hours) compared to immediate-release formulations (2.9 hours), but provides more consistent blood pressure control throughout the dosing interval 2
Angina Relief Timeline
- Antianginal effects begin within 3 hours of oral administration, with significant improvements in exercise tolerance and reduction in ST-segment depression documented at this timepoint 3
- Plasma concentrations at 3 hours (mean 13.9 ng/ml) correlate significantly with increased time to onset of ischemic ST-segment changes and decreased extent of myocardial ischemia 3
- Symptomatic improvement for variant (Prinzmetal's) angina occurs within the first week of therapy, with 41% reduction in angina frequency at 120 mg daily and 68% reduction at 240 mg daily 4
Clinical Dosing Considerations
- Starting dose is typically 120 mg twice daily, with blood pressure and symptom assessment after one week to determine if dose escalation to 240 mg or 360 mg twice daily is needed 5, 1
- Optimal therapeutic response is usually achieved within 4 weeks of maintenance therapy at the appropriate dose 2
- Heart rate reduction during exercise occurs within hours of administration, decreasing from 119 to 107 beats/min during submaximal exercise at 3 hours post-dose 3
Important Safety Caveats
- Avoid in patients with severe left ventricular dysfunction or pulmonary edema, as diltiazem has prominent negative inotropic effects and can worsen heart failure 6
- Contraindicated in second- or third-degree AV block without a functioning pacemaker, as diltiazem has significant AV and sinus node depressant effects 6
- Exercise caution when combining with beta-blockers, as the combination may cause additive depression of cardiac function, heart rate, and AV conduction—though this combination can be effective for refractory angina when carefully monitored 6, 7