Amlodipine (Norvasc)

Amlodipine is a calcium channel blocker of the dihydropyridine type. It blocks calcium entry into the smooth muscle of the arterial wall. Without calcium the muscle cannot contract, the vessels widen, peripheral resistance falls and blood pressure with it.

The point that makes it interesting in a training context: amlodipine acts almost exclusively on the vessels and barely on the heart itself. It does not lower heart rate. A beta blocker caps your maximum heart rate and with it, measurably, your endurance performance. A calcium channel blocker does not.

This information is for research and educational purposes only. No medical advice.

The half-life of 30 to 50 hours is unusually long for a blood pressure agent and explains three things at once. First, one dose per day is enough. Second, it takes seven to ten days for the full effect to appear, because the level has to build. Third, it keeps working for days after stopping.

In practice: anyone measuring after three days and finding the target range unmet measured too early. Increasing at that point regularly drives pressure unnecessarily low once the build-up finishes. Conversely, a missed dose does not need catching up, the buffer is too large for that.

The evidence is unusually dense for a blood pressure agent, and it is not uniformly flattering. ALLHAT (JAMA 2002) compared over 33,000 high-risk patients and found no difference in the primary endpoint between amlodipine and the diuretic chlorthalidone. But heart failure occurred 38 percent more often under amlodipine. That is the single most important caveat about the substance and belongs, honestly, on every page about it.

ASCOT-BPLA (Lancet 2005) came out clearly in amlodipine's favour: an amlodipine-based regimen beat an atenolol-based one on strokes and all-cause mortality. VALUE (Lancet 2004) showed faster pressure reduction in the first months and fewer heart attacks under amlodipine than under valsartan.

PRAISE (NEJM 1996) is the reason amlodipine may be used at all in existing heart failure: it proved safe, while older calcium channel blockers caused harm in that setting.

• Swollen ankles: by far the most common report, mostly in the evening and mostly at 10mg. Important to understand: this is not fluid retention in the sense of an excess, it is a local shift of fluid into tissue, because the small arteries widen more than the veins do. Diuretics do not help against it. Anyone affected usually does better on a lower dose plus a second agent than on 10mg alone.
• Headache and flushing: typical in the first days, usually settles on its own.
• Dizziness on standing: a sign that pressure sits too low.
• Gum overgrowth: rare, but documented and relevant with long-term use.

Store dry, at room temperature and protected from light. Keep out of reach of children.