Amlodipin: the pathway in the body

Amlodipin is part of the pathway “Amlodipine”. This page shows the whole pathway; the station of Amlodipin is highlighted.

Where this laboratory value sits: Amlodipine — tablet, swallowed. Amlodipine is swallowed as a tablet. It belongs to the dihydropyridines and is already the form that acts at the channel; nothing has to be cleaved off first in the body. It inhibits calcium inflow into vessel muscle. Source 8

In brief

Amlodipine is a dihydropyridine. It settles into a niche of the voltage-gated calcium channel of the L-type and lets less calcium flow into the vessel muscle cell. The channel is a door, not a store. The vessel muscle thus relaxes, and the vessel widens.

The pathway step by step

Each station states what the compound does there. Three signs: ↑ supplies — builds up or makes available · ↓ depletes — inhibits, consumes or withholds · ↕ both, depending on amount. Behind it stands what the statement rests on: established physiology, observed in studies, or contested. The signs do not grade; they name the direction.

1. Amlodipine → Slow absorption The substance is absorbed slowly. The label puts the peak in the blood several hours after swallowing and notes that food does not change the amount absorbed. The amount in the blood thus rises gradually. Source 8↑ supplies Absorption in the gut brings the active substance into the blood. Because this happens slowly, the amount in the blood rises over hours, and the substance arrives at the channel gradually. established physiology Source 8
   ⚖ When the balance tips

   too much — If more active substance enters the blood than the liver breaks down in the same time, the amount in the blood keeps rising over days until inflow and breakdown balance.

   too little — If little active substance enters the blood, the amount there stays low, and correspondingly little amlodipine is present at the channel.

   established physiology · Source 8

2. Slow absorption → Charged in the body At the pH that prevails in the body, amlodipine carries a charge. It settles onto the channel only gradually and comes off just as gradually; the action therefore sets in slowly. The widening of the vessels thus lasts evenly. Source 8↑ supplies The charged form binds to the channel slowly and stays there for a long time. This produces not a sudden widening of the vessels but an even one that lasts through the day. established physiology Source 8, 3
   ⚖ When the balance tips

   too much — If a lot of bound amlodipine is present, it comes off only gradually because binding is slow; the widening of the vessels then persists even after the blood level falls.

   too little — If little is bound, this too has an effect only gradually because of the slow kinetics: the channels become free again step by step.

   established physiology · Source 8

3. Charged in the body → Elimination The liver converts the greater part into inactive breakdown products. These leave the body mostly in the urine. The conversion is slow; amlodipine stays in the body for a long time. Source 8↓ depletes The liver removes the active substance from the blood by converting it into inactive breakdown products. This conversion is slow, which is why amlodipine stays in the body for a long time. established physiology Source 8
   ⚖ When the balance tips

   too much — If the liver breaks it down briskly, the amount in the blood falls faster, and less active substance is present at the channel.

   too little — If the liver works more slowly, for example with reduced liver function or in older age, amlodipine stays longer in the blood, and its amount there is higher.

   established physiology · Source 8

4. Voltage at the cell wall → L-type channel · voltage sensor The voltage-gated calcium channel of the L-type opens. In the smooth muscle of the vessel wall it is the main route by which calcium comes into the cell from outside. Much inflow narrows the vessel, little inflow widens it. Source 2, 8↑ supplies The open L-type channel lets calcium into the vessel muscle cell from outside. This inflow is the signal that makes the muscle cell contract. established physiology Source 2
   ⚖ When the balance tips

   too much — If many channels are open, a lot of calcium flows in; the muscle cell contracts more strongly, and the vessel becomes narrower.

   too little — If few channels are open, little calcium enters the cell from outside; the muscle cell relaxes, and the vessel widens.

   established physiology · Source 2, 6

5. L-type channel → Calcium in the cell L-type channel The inflowing calcium makes the amount of free calcium inside the cell rise. It is this rise alone that is read; at rest the cell holds the amount very low. Pumps quickly move it out again. Source 6, 2↕ both, depending on amount A brief rise in free calcium is the signal for contraction. If calcium stays high for long, it also switches on processes in the cell that strain it; the cell therefore pumps it out again quickly. established physiology Source 6
   ⚖ When the balance tips

   too much — If a lot of free calcium remains inside the cell, pumps and exchangers run at full speed and use up ATP; at the same time the muscle cell stays tense.

   too little — If free calcium hardly rises, little binds to calmodulin, the kinase stays idle, and the muscle cell remains relaxed.

   established physiology · Source 6

6. Calcium in the cell → Calcium-calmodulin · calmodulin Calcium binds to calmodulin, a small protein. The loaded calmodulin changes its shape and can now dock onto myosin light chain kinase. The calcium rise thus becomes enzyme activity. Source 6, 5↑ supplies Loaded calmodulin switches on myosin light chain kinase. It translates the rise in calcium into enzyme activity. established physiology Source 6, 5
   ⚖ When the balance tips

   too much — If a lot of calcium-calmodulin is present, the kinase is fully active, and the light chain of myosin is loaded with phosphate quickly.

   too little — If little calcium-calmodulin is present, the kinase stays largely switched off, and the phosphatase wins the contest.

   established physiology · Source 5

7. Calcium-calmodulin → Phosphate on myosin MLCK · Mg-ATP Only with calcium-calmodulin bound does myosin light chain kinase work. It transfers phosphate from Mg-ATP onto the light chain of myosin; after that, myosin and actin engage with each other. The vessel wall tenses. Source 5, 4↑ supplies With phosphate on the light chain, myosin and actin engage; the muscle cell contracts, and the vessel wall tenses. On this depends how wide the vessel is. established physiology Source 4, 5
   ⚖ When the balance tips

   too much — If a lot of myosin is loaded with phosphate, the vessel muscle stays tense, the vessel narrow and the resistance in the circulation high.

   too little — If little myosin is loaded with phosphate, myosin and actin separate, the vessel muscle relaxes, and the vessel widens.

   established physiology · Source 4

8. Store inside the cell → Calcium in the cell IP3 receptor The inflowing calcium makes the amount of free calcium inside the cell rise. It is this rise alone that is read; at rest the cell holds the amount very low. Pumps quickly move it out again. Source 6, 2↕ both, depending on amount A brief rise in free calcium is the signal for contraction. If calcium stays high for long, it also switches on processes in the cell that strain it; the cell therefore pumps it out again quickly. established physiology Source 6
   ⚖ When the balance tips

   too much — If a lot of free calcium remains inside the cell, pumps and exchangers run at full speed and use up ATP; at the same time the muscle cell stays tense.

   too little — If free calcium hardly rises, little binds to calmodulin, the kinase stays idle, and the muscle cell remains relaxed.

   established physiology · Source 6

Further stations

• Amlodipine — tablet, swallowed Amlodipine is swallowed as a tablet. It belongs to the dihydropyridines and is already the form that acts at the channel; nothing has to be cleaved off first in the body. It inhibits calcium inflow into vessel muscle. Source 8↓ depletes Amlodipine inhibits the inflow of calcium into the smooth muscle of the vessels and, more weakly, into heart muscle. The vessel muscle relaxes, the vessel widens, and the resistance in the circulation falls. established physiology Source 8
  ⚖ When the balance tips

  too much — If a lot of amlodipine is present, more L-type channels in the vessel wall are occupied; the vessels widen further, and blood pressure falls further.

  too little — If little amlodipine is present, most channels remain free; calcium flows in as usual, and the tension of the vessel muscle stays almost unchanged.

  established physiology · Source 8

• Niche at the channel — to the side, not in the pore Dihydropyridines do not settle in the middle of the pore but into a niche on the side of the channel wall. Structural images place this spot at the junction between the third and the fourth repeat of the channel. The channel then opens less often. Source 3, 1, 8↓ depletes In the side niche, the dihydropyridine holds the channel preferentially in the closed, inactivated state. It opens less often, and less calcium enters the cell from outside. established physiology Source 3, 1
  ⚖ When the balance tips

  too much — If many niches are occupied, a large share of the channels stays closed; the calcium inflow is so small that the muscle cell barely builds up tension.

  too little — If few niches are occupied, the channels open as usual when the voltage changes, and the inflow of calcium is maintained.

  established physiology · Source 1, 2

• Voltage at the cell wall — set by potassium channels The voltage across the cell wall decides whether the channel opens. Potassium channels set it; when the cell becomes less negative, the channel opens. Open potassium channels keep it shut. Source 7, 2↑ supplies If the cell wall becomes less negative, the voltage opens the L-type channel. Open potassium channels keep the voltage negative and thus the channel closed; in this way they set the basic tone of the vessel wall. established physiology Source 7, 2
  ⚖ When the balance tips

  too much — If the cell wall becomes much less negative, for example when potassium channels close, more L-type channels open, more calcium flows in, and the vessel contracts.

  too little — If the cell wall stays strongly negative because many potassium channels are open, the L-type channels stay shut; little calcium flows in, and the vessel relaxes.

  established physiology · Source 7

• Store inside the cell — endoplasmic reticulum Calcium can also come from within: the messenger IP3 opens channels at the endoplasmic reticulum, the store of the cell. This route does not pass through the cell wall. Amlodipine does not act here. Source 6↑ supplies The internal store supplies calcium in response to a signal from outside, such as a messenger at a receptor. Amlodipine does not act here; this route stays open even when L-type channels are occupied. established physiology Source 6
  ⚖ When the balance tips

  too much — If the store releases a lot of calcium, free calcium rises even without inflow from outside; the SERCA pump then refills the store using ATP.

  too little — If the store is poorly filled, it can release only a little calcium in response to a signal, and the rise inside the cell is smaller.

  established physiology · Source 6

• Myosin phosphatase — counterpart of the kinase Myosin light chain phosphatase takes the phosphate off again. How heavily the light chain is loaded follows at any moment from the contest between kinase and phosphatase. The muscle cell then relaxes. Source 4↓ depletes The phosphatase removes the phosphate from the light chain and lets the muscle cell relax. If it is inhibited via kinases, tension stays higher at the same calcium level. established physiology Source 4
  ⚖ When the balance tips

  too much — If the phosphatase is very active, myosin quickly loses its phosphate; the muscle cell relaxes even if some calcium is still present.

  too little — If the phosphatase is inhibited, phosphate stays on myosin longer; the muscle cell stays tense even with little calcium.

  established physiology · Source 4

What depends on the calcium influx

• Calcium — The L-type channel is the route by which calcium flows from outside into the smooth muscle cell of the vessel wall Source 2, 8

What takes part in these steps

• Magnesium — Myosin light chain kinase transfers phosphate from Mg-ATP; without magnesium it does not work; then myosin engages Source 5
• Potassium — Potassium channels set the voltage at the cell wall; on it hangs whether the L-type channel opens Source 7
• Sodium — Drive of the NCX exchanger, which carries calcium out of the cell in trade against sodium; inner calcium thus falls Source 6
• ATP — Supplies the kinase with phosphate and drives the pumps SERCA and PMCA that fetch calcium out of the cytoplasm Source 6, 5
• Inositol — Building block of PIP2, from which the messenger IP3 is cleaved that opens the store of the cell; calcium is released Source 6

What the prescribing information states

Controlled trials in the United States in which amlodipine was compared directly against placebo. The prescribing information sorts these four reactions by the amount of the substance: steps 1 to 3 are the three amounts studied, from the smallest to the largest. The figures apply to these trials.

How to read the table: each row carries four figures, and only the comparison says something. For fluid retention the gap to placebo grows markedly with the amount of the substance; for dizziness it stays small. There is no column with another medicine here — this prescribing information compares against placebo alone. And for this table it selected only reactions that were more frequent on amlodipine.

Four further reactions are named without a link to the amount; they come from all placebo-controlled trials together, 1,730 adults on amlodipine against 1,250 on placebo: fatigue 4.5 against 2.8 of 100, nausea 2.9 against 1.9, abdominal pain 1.6 against 0.3, sleepiness 1.4 against 0.6. Reactions reported after approval are not listed here — the prescribing information notes that neither a frequency nor a causal relationship can be derived from them.

Sources

1. Catterall WA, Swanson TM. Structure and Pharmacology of Voltage-Gated Sodium and Calcium Channels. Annu Rev Pharmacol Toxicol 2020 · PubMed 31537174
2. Zamponi GW, Striessnig J, Koschak A et al. The Physiology, Pathology, and Pharmacology of Voltage-Gated Calcium Channels and Their Future Therapeutic Potential. Pharmacol Rev 2015 · PubMed 26362469
3. Zhao Y, Huang G, Wu J et al. Molecular Basis for Ligand Modulation of a Mammalian Voltage-Gated Ca2+ Channel. Cell 2019 · PubMed 31150622
4. Somlyo AP, Somlyo AV. Ca2+ sensitivity of smooth muscle and nonmuscle myosin II: modulated by G proteins, kinases, and myosin phosphatase. Physiol Rev 2003 · PubMed 14506307
5. Ran Q, Tian H, Lin J et al. Action and therapeutic targets of myosin light chain kinase, an important cardiovascular signaling mechanism. Pharmacol Res 2024 · PubMed 38944220
6. Berridge MJ, Bootman MD, Roderick HL. Calcium signalling: dynamics, homeostasis and remodelling. Nat Rev Mol Cell Biol 2003 · PubMed 12838335
7. Jackson WF. Potassium Channels in Regulation of Vascular Smooth Muscle Contraction and Growth. Adv Pharmacol 2017 · PubMed 28212804
8. US prescribing information (United States): Amlodipine Besylate Tablets, DailyMed, version of 17 Sept 2026, sections 12.1 Mechanism of Action, 12.2 Pharmacodynamics and 12.3 Pharmacokinetics · Prescribing information
9. US prescribing information (United States): Amlodipine Besylate Tablets, DailyMed, version of 17 Sept 2026, sections 6.1 Clinical Trials Experience and 6.2 Postmarketing Experience · Prescribing information

Whole pathway: Amlodipine

Related pathways

• Candesartan — calcium in the cell

As of 2026-09-25. Draft, written by Claude to schema v2; sources checked in PubMed; expert approval pending
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