From the Guidelines
The half-life of amlodipine is approximately 34-50 hours. This is based on the most recent and highest quality study available, which suggests that amlodipine is cleared slowly, with a half-life ranging from 34 to 50 hours 1. The long half-life of amlodipine allows for once-daily dosing, which is beneficial for maintaining stable blood pressure control throughout a 24-hour period and improves medication adherence due to the convenience of once-daily dosing. Some key points to consider about the pharmacokinetics of amlodipine include:
- Amlodipine's half-life may be extended further in elderly patients or those with hepatic impairment, sometimes necessitating dose adjustments in these populations
- The drug's extended duration of action means that if a dose is missed, blood pressure control is generally maintained, though patients should take their next scheduled dose as normal rather than doubling up
- Amlodipine is primarily metabolized in the liver, and its clearance may be altered in patients with impaired renal function, as the fraction of renal elimination is also important for those drugs that are excreted in urine 1.
From the FDA Drug Label
Elimination from the plasma is biphasic with a terminal elimination half-life of about 30 to 50 hours. The half-life of amlodipine is 30 to 50 hours 2.
From the Research
Half-Life of Amlodipine
- The half-life of amlodipine, a calcium channel blocker, is reported to be between 40-60 hours 3, 40-50 hours 4, and 35-50 hours 5.
- This long elimination half-life allows for once-daily dosing and sustains the anti-hypertensive effect for more than 24 hours following a single dose 5.
- The pharmacokinetic profile of amlodipine is characterized by low clearance, high volume of distribution, and high degree of protein binding, resulting in a long elimination half-life 4, 6.
Factors Influencing Half-Life
- Age, severe hepatic impairment, and severe renal impairment may influence the pharmacokinetic profile of amlodipine, leading to higher plasma concentrations and longer half-lives 4.
- However, the pharmacokinetics of amlodipine are not significantly altered in elderly or renally impaired patients 6.
Clinical Implications
- The long half-life of amlodipine allows for maintained blood pressure control even when a dose has been missed, providing continuous protection in case of incidental noncompliance 5.
- Amlodipine's pharmacokinetic properties avoid sharp fluctuations in plasma levels, reducing the risk of vasodilatation-induced side effects such as tachycardia, headache, and flushing 6.