What is the elimination half‑life of amlodipine in healthy adults, and how is it altered in patients with hepatic impairment or in the elderly?

Amlodipine Half-Life

The elimination half-life of amlodipine is 30-50 hours in healthy adults, extending to approximately 56-60 hours in patients with hepatic impairment and 48-58 hours in elderly patients. 1

Half-Life in Healthy Adults

• The FDA label specifies a terminal elimination half-life of approximately 30-50 hours for amlodipine in healthy adults 1
• Research studies consistently report a half-life of 34-50 hours, with most values clustering around 40-50 hours 2, 3, 4
• Steady-state plasma levels are reached after 7-8 days of consecutive daily dosing, reflecting this prolonged elimination 1

Half-Life in Hepatic Impairment

• Patients with severe hepatic impairment have a significantly prolonged elimination half-life of approximately 56 hours (compared to 34 hours in healthy subjects), representing a 65% increase 1, 2
• The FDA label explicitly warns that the plasma elimination half-life is 56 hours in patients with impaired hepatic function, necessitating slow dose titration 1
• This prolongation occurs because amlodipine is extensively metabolized by the liver (approximately 90% converted to inactive metabolites), making hepatic clearance the primary elimination pathway 1, 2

Half-Life in Elderly Patients

• Elderly patients demonstrate a significantly prolonged elimination half-life of 48-58 hours (versus 35-42 hours in younger patients), representing a 30-40% increase 2, 5
• This prolongation results from decreased clearance (19 L/hr in elderly versus 25 L/hr in young patients) rather than changes in volume of distribution 5
• The FDA label notes that elderly patients have decreased clearance with a resulting 40-60% increase in AUC, warranting consideration of lower initial doses 1

Clinical Context from Adherence Testing

• Amlodipine's long half-life (34-50 hours) means the drug is cleared slowly, allowing sporadic dosing to still produce analytically positive results up to a week after the last ingestion 6
• Despite theoretical concerns about false positives in adherence testing due to this long half-life, recent evidence shows no correlation between half-life and adherence detection rates for antihypertensive medications 6

Renal Impairment

• The pharmacokinetics of amlodipine are not significantly influenced by renal impairment, as only 10% of the parent compound is excreted renally 1, 3
• Patients with renal failure may receive the usual initial dose without adjustment 1