How calcium channel blockers are tested on Step 1

Questions ask which class fits rate control versus blood-pressure control, explain ankle edema or constipation, or warn about combining verapamil with a beta blocker.

workspace_premium Vessel vs heart

Selectivity runs on a spectrum: nifedipine and amlodipine (vessels) > diltiazem > verapamil (heart). Remember "verapamil = ventricle."

Mechanism

In vascular smooth muscle, Ca²⁺ entry activates calmodulin and myosin light-chain kinase, causing contraction. In the SA and AV nodes, the upstroke of the action potential is carried by Ca²⁺.

L-typechannelBlocked↓ Ca²⁺entryInto smoothmuscleCalmodulinLessactivatedMLCKLess myosinphosphorylationRelaxationArteriolardilation
Smooth-muscle relaxation. CCBs dilate arterioles much more than veins, so preload is little affected.

Dihydropyridines vs non-dihydropyridines

The two groups have different targets, uses, and adverse effects.

DihydropyridinesAmlodipine, nifedipine, nicardipine,clevidipine, nimodipineVascular smooth muscleHypertension, angina (vasospastic),RaynaudReflex tachycardia (short-acting)Edema, flushing, headache, gingivalhyperplasiaNon-dihydropyridinesVerapamil, diltiazemHeart: SA and AV nodes, myocardiumRate control of AF and flutter, SVT,anginaBradycardia, AV block, ↓ contractilityConstipation (verapamil), gingivalhyperplasiavs
Two kinds of CCB. Short-acting nifedipine is avoided in acute coronary syndromes because reflex tachycardia can worsen ischemia.
AgentNotable use
AmlodipineLong-acting, first-line for hypertension; safe in HFrEF
Nifedipine (extended-release)Hypertension in pregnancy; Raynaud phenomenon
Nicardipine, clevidipineIV for hypertensive emergency
NimodipinePrevents cerebral vasospasm after subarachnoid hemorrhage
VerapamilSVT, rate control, cluster headache prophylaxis
DiltiazemRate control of atrial fibrillation; angina

Verapamil inhibits P-glycoprotein and CYP3A4, raising digoxin and statin levels.

Adverse effects and interactions

Adverse effects follow the tissue each group targets.

CCB adverse effectsPeripheraledemaPrecapillarydilation (DHP)ReflextachycardiaShort-actingDHPBradycardia,AV blockVerapamil,diltiazemConstipationVerapamilGingivalhyperplasiaBoth groups
CCB adverse effects. The edema does not respond to diuretics because it reflects capillary pressure, not volume overload; adding an ACE inhibitor or ARB helps.
AvoidReason
Verapamil or diltiazem + β blockerAdditive AV block, bradycardia, heart failure
Verapamil or diltiazem in HFrEFNegative inotropy worsens heart failure
Verapamil in Wolff-Parkinson-White with AFAV nodal block can accelerate conduction through the accessory pathway
Short-acting nifedipine in ACSReflex tachycardia and hypotension

CCB overdose: hypotension, bradycardia, and hyperglycemia (insulin release depends on Ca²⁺) — treat with calcium, high-dose insulin, and vasopressors.

Clinical application

The choice of CCB follows the goal: lower pressure or slow the heart.

functions Worked example — why are the ankles swollen?

A 66-year-old started amlodipine 10 mg for hypertension. Six weeks later her ankles are swollen. Weight, JVP, and albumin are normal. Why did edema develop, and will furosemide help?

  1. Amlodipine dilates precapillary arterioles more than postcapillary venules.
  2. Capillary hydrostatic pressure rises, pushing fluid into the interstitium.
  3. Total body volume is not increased, so diuretics have little effect.
  4. Lowering the dose or adding an ACE inhibitor or ARB (which dilates venules) reduces the edema.

Answer. Edema from increased capillary hydrostatic pressure, not volume overload. Furosemide will not help much; reduce the dose or add an ACE inhibitor or ARB.