Amlodipine half life
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Amlodipine Half-Life: Pharmacokinetics and Clinical Implications
Introduction to Amlodipine Half-Life
Amlodipine, a dihydropyridine calcium antagonist, is widely used for the treatment of hypertension and angina. One of its key pharmacokinetic properties is its long elimination half-life, which significantly influences its clinical use and dosing regimen.
Pharmacokinetic Profile of Amlodipine
Intravenous and Oral Administration
Studies have shown that the half-life of amlodipine varies slightly depending on the mode of administration. When administered intravenously at a single dose of 10 mg, the mean plasma half-life is approximately 34 hours 1. In contrast, oral administration of the same dose results in a mean plasma half-life of about 36 hours 1. This slight difference is attributed to the drug's pharmacokinetic properties, including its high volume of distribution and extensive protein binding 4.
Repeated Dosing and Steady-State Concentrations
With repeated oral administration (once daily for 14 days), the half-life of amlodipine extends to around 45 hours, indicating a threefold accumulation and steady-state plasma concentrations being reached after seven doses 1. This extended half-life supports the drug's suitability for once-daily dosing, ensuring consistent therapeutic levels with minimal fluctuations 4.
Variability in Half-Life
Influence of Age and Health Conditions
The half-life of amlodipine can be significantly prolonged in certain populations. For instance, elderly patients exhibit a longer half-life (48 hours) compared to younger individuals, likely due to decreased clearance 57. Similarly, patients with severe hepatic impairment may experience a half-life of up to 60 hours, suggesting greater drug accumulation due to reduced metabolic clearance 3.
Comparison with Other Calcium Channel Blockers
Amlodipine's half-life is notably longer than that of other dihydropyridine calcium antagonists, which typically range from 3 to 10 hours, and nondihydropyridine calcium antagonists, which have half-lives of 3 to 6 hours 3. This extended half-life contributes to its prolonged duration of action and makes it more effective in maintaining blood pressure control even during short interruptions in therapy 8.
Clinical Implications
Efficacy in Hypertension and Angina
The long half-life of amlodipine ensures sustained antihypertensive and antianginal effects over a 24-hour period, with minimal trough-to-peak variability 10. This characteristic is particularly beneficial for patients with chronic stable angina, as it reduces both symptomatic and asymptomatic ischemic events throughout the day 2.
Dosing Convenience and Compliance
The extended half-life of amlodipine allows for once-daily dosing, which enhances patient compliance and simplifies the treatment regimen. This is especially advantageous for elderly patients and those with comorbid conditions, who may have difficulty adhering to more frequent dosing schedules 57.
Conclusion
Amlodipine's long elimination half-life, ranging from 34 to 50 hours depending on various factors, underpins its effectiveness as a once-daily medication for hypertension and angina. This pharmacokinetic property not only ensures sustained therapeutic effects but also improves patient compliance, making amlodipine a valuable option in the management of cardiovascular conditions.
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