From the FDA Drug Label
The plasma elimination half-life following single or multiple drug administration is approximately 3.0 to 4.5 hours. The duration of effect of Diltiazem is related to its plasma elimination half-life, which is approximately 3.0 to 4.5 hours 1.
- The half-life indicates the time it takes for the plasma concentration of the drug to reduce by half.
- Based on this information, the duration of effect of Diltiazem can be estimated to be around 6 to 9 hours, considering the time it takes for the drug to be eliminated from the body.
From the Research
Diltiazem's duration of effect can last up to 24 hours with extended-release formulations, allowing for once or twice daily dosing, as seen in the study by 2, which demonstrated a novel diltiazem HCl extended-release tablet formulation for evening administration. The duration of effect of diltiazem varies based on its formulation.
- Immediate-release diltiazem typically lasts 6-8 hours, requiring multiple daily doses.
- Extended-release formulations provide 12-24 hours of effect, allowing for once or twice daily dosing. The standard extended-release versions are dosed once daily, while some formulations like Dilacor XR may require twice-daily administration. When used for acute situations like atrial fibrillation with rapid ventricular response, IV diltiazem's effects last about 2-4 hours. Diltiazem works by blocking calcium channels in cardiac and vascular smooth muscle, reducing heart rate, contractility, and blood pressure. The drug's duration is influenced by its half-life of 3-8 hours, which extends to 5-10 hours with extended-release formulations, as shown in the study by 3. Patients with liver dysfunction may experience prolonged effects due to decreased metabolism of the drug. For optimal therapeutic effect, it's essential to maintain consistent blood levels by taking extended-release formulations at the same time each day, as demonstrated by the study 2, which found that evening administration of diltiazem HCl ER tablets exhibited 17% and 22% greater bioavailability compared to morning administration. This suggests that evening administration of extended-release diltiazem formulations may provide better coverage during the critical morning hours, when blood pressure and cardiovascular events are highest, as supported by the study 2. Overall, the choice of diltiazem formulation and administration time should be based on individual patient needs and response to treatment, with consideration of the pharmacokinetic properties and duration of effect, as discussed in the studies 3, 4, 5, 6, 2.