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{{BioPsy}}
  
{{BioPsy}}
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{{PsyPerspective}}
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{{Main|Channel blockers}}
   
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A '''calcium channel blocker''' ('''CCB''') is a chemical that disrupts the movement of [[calcium]] (Ca<sup>2+</sup>) through [[calcium channel]]s.<ref>{{DorlandsDict|nine/20112461|calcium channel blocker}}</ref> Calcium channel blockers are used as [[antihypertensive drug]]s, i.e. as medications to decrease [[blood pressure]] in patients with [[hypertension]]. CCBs are particularly effective against large vessel stiffness, one of the common causes of elevated systolic blood pressure in elderly patients.<ref name=nps01>{{ cite journal | author = Nelson M | title = Drug treatment of elevated blood pressure | journal = Australian Prescriber | year = 2010 | volume = 33 | issue = 4 | pages = 108–112 | url = http://www.australianprescriber.com/upload/pdf/articles/1120.pdf | format = pdf }}</ref> Calcium channel blockers are also frequently used to alter [[heart rate]], to prevent [[cerebral vasospasm]], and to reduce [[chest pain]] caused by [[angina pectoris]]. One type of calcium channel blocker is used experimentally to prevent [[migraine]], and another one is used as a powerful painkiller.
−
'''Calcium channel blockers''' are a class of [[medication|drugs]] with effects on many excitable cells of the body, like the muscle of the [[heart]], smooth muscles of the vessels or [[neuron]] cells. The latter are used as [[antiepileptics]] and are not covered in this article.
  
   
  +
Despite their effectiveness, CCB's often have a high mortality rate over extended periods of use, and have been known to have multiple side effects.<ref>{{cite web|url=http://www.medicinenet.com/calcium_channel_blockers/page2.htm#side%20effects|title=Calcium Channel Blockers|page=2|work=MedicineNet}}</ref> Potential major risks however were mainly found to be associated with short-acting CCBs.<ref>{{cite web|url=http://cmbi.bjmu.edu.cn/uptodate/hypertension/drg%20therpy/Major%20side%20effects%20and%20safety%20of%20calcium%20channel%20blockers.htm|title=Major side effects and safety of calcium channel blockers|author1=Norman M Kaplan, MD|author2=Burton D Rose, MD|date=Apr 3, 2000|work=Chinese Medical & Biological Information}}</ref>
−
The main action of calcium channel blockers is to lower the [[blood pressure]]. It is for this action that it is used in individuals with [[hypertension]].
  
   
  ⚫
==Mechanism of action==
−
== Explanation ==
  
  +
[[File:Calciumkanal_Förstermann.jpg|thumb|right|250px|A calcium channel embedded in a cell membrane.]]
  +
In the body's tissues, the concentration of calcium ions (Ca<sup>2+</sup>) outside of cells is normally about tenthousandfold higher than the concentration inside of cells. Embedded in the [[cell membrane|membrane]] of some cells are [[calcium channel]]s. When these cells receive a certain signal, the channels open, letting calcium rush into the cell. The resulting increase in intracellular calcium has different effects in different types of cells. Calcium channel blockers prevent or reduce the opening of these channels and thereby reduce these effects.
   
  +
There are several types of calcium channels, and a number of classes of calcium channel blockers, but almost all of them preferentially or exclusively block the [[L-type calcium channel|L-type]] [[voltage-gated calcium channel]].<ref name=mech>{{cite journal|author=Yousef ''et al.''|title=The mechanism of action of calcium channel blockers in the treatment of diabetic nephropathy|journal=Int J Diabetes & Metabolism|year=2005|volume=13|pages=76–82|pmid=|url=http://ijod.uaeu.ac.ae/iss_1302/b.pdf}}</ref>
−
Most calcium channel blockers decrease the force of contraction of the [[myocardium]] (muscle of the heart). This is known as the negative inotropic effect of calcium channel blockers. It is because of the negative inotropic effects of most calcium channel blockers that they are avoided (or used with caution) in individuals with [[cardiomyopathy]].
  
   
  +
L-type calcium channels are responsible for excitation-[[muscle contraction|contraction]] coupling of [[skeletal muscle|skeletal]], [[smooth muscle|smooth]], and [[cardiac muscle]] and for [[hormone]] secretion in [[endocrine system|endocrine cells]]. In the heart they are also involved in the conduction of the [[pacemaker]] signals. CCBs used as medications primarily have three effects:
⚫
:Many calcium channel blockers also slow down the conduction of electrical activity within the heart, by blocking the calcium channel during the plateau phase of the [[action potential]] of the heart (see: [[cardiac action potential]]). This causes a lowering of the [[heart rate]] and may cause [[heart block]]s. This is known as the negative chronotropic effect of calcium channel blockers. The negative chronotropic effects of calcium channel blockers make them a commonly used class of agents in individuals with [[atrial fibrillation]] or [[atrial flutter|flutter]] in whom control of the heart rate is an issue.
  
  +
* by acting on [[vascular smooth muscle]] they reduce contraction of the arteries and cause an increase in [[artery|arterial]] diameter, a phenomenon called [[vasodilation]] (CCBs do not work on [[vein|venous]] smooth muscle)
  +
* by acting on cardiac muscles ([[myocardium]]), they reduce the force of contraction of the heart
  +
* by slowing down the conduction of electrical activity within the heart, they slow down the heart beat.
   
  +
Since blood pressure is determined by cardiac output and peripheral resistance, CCBs reduce blood pressure. With relatively low blood pressure, the [[afterload]] on the heart decreases; this decreases how hard the heart must work to eject blood into the aorta, and so the amount of oxygen required by the heart decreases accordingly. This can help ameliorate symptoms of [[ischaemic heart disease]] such as [[angina pectoris]].
⚫
==Mechanism of action==
  
   
  ⚫
Reducing the force of contraction of the myocardium is known as the negative [[inotropic]] effect of calcium channel blockers. Slowing down the conduction of electrical activity within the heart, by blocking the calcium channel during the plateau phase of the [[action potential]] of the heart (see: [[cardiac action potential]]), results in a negative [[chronotropic]] effect, or a lowering of [[heart rate]]. This can increase the potential for [[heart block]]. The negative chronotropic effects of calcium channel blockers make them a commonly used class of agents in individuals with [[atrial fibrillation]] or [[atrial flutter|flutter]] in whom control of the heart rate is generally a goal. Negative chronotropy can be beneficial when treating a variety of disease processes because lower heart rates represent lower cardiac oxygen requirements. Elevated heart rate can result in significantly higher "cardiac work," which can result in symptoms of angina.
−
Calcium channel blockers work by blocking L-type voltage gated calcium channels ([[VGCC]]) in the [[heart]] and in the [[blood vessel]]s. This prevents calcium levels from increasing as much in the cells when stimulated, leading to less contraction.
  
   
  +
The class of CCBs known as ''dihydropyridines'' mainly affect arterial vascular smooth muscle and lower blood pressure by causing vasodilation. The ''phenylalkylamine'' class of CCBs mainly affect the cells of the heart and have negative inotropic and negative chronotropic effects. The ''benzothiazepine'' class of CCBs combine effects of the other two classes.
−
This decreases [[total peripheral resistance]] by dilating the blood vessels, and decreases [[cardiac output]] by lowering the force of contraction. Because resistance and output drop, so does blood pressure.
  
   
  +
It is because of the negative inotropic effects that the nondihydropyridine calcium channel blockers should be avoided (or used with caution) in individuals with [[cardiomyopathy]].<ref>{{cite book | author = Lehne R | title = Pharmacology for Nursing Care | edition = 7th | year = 2010| publisher = Saunders Elsevier | location = St. Louis, Missouri | isbn = 978-1-4160-6249-3 | page = 505 }}</ref>
−
With low blood pressure, the heart does not have to work as hard; this can ease problems with [[cardiomyopathy]] and [[coronary heart disease|coronary disease]].
  
   
  +
Unlike [[beta blocker]]s, calcium channel blockers do not decrease the responsiveness of the heart to input from the [[sympathetic nervous system]]. Since moment-to-moment blood pressure regulation is carried out by the sympathetic nervous system (via the [[baroreceptor reflex]]), calcium channel blockers allow blood pressure to be maintained more effectively than do beta blockers. However, because dihydropyridine calcium channel blockers result in a decrease in blood pressure, the baroreceptor reflex often initiates a reflexive increase in sympathetic activity leading to increased heart rate and contractility.
−
Unlike with [[beta-blocker]]s, the heart is still responsive to [[sympathetic nervous system]] stimulation, so blood pressure can be maintained more effectively.
  
   
  +
Ionic calcium is antagonized by magnesium ions in the nervous system. Because of this, bioavailable supplements of magnesium, possibly including [[magnesium chloride]], [[magnesium lactate]], and [[magnesium aspartate]], may increase or enhance the effects of calcium channel blockade.<ref>{{ cite journal | author = Iseri LT, French JH | title = Magnesium: Nature's Physiologic Calcium Blocker | journal = American Heart Journal | year = 1984 | volume = 108 | issue = 1 | pages = 188–193 | doi = 10.1016/0002-8703(84)90572-6 | pmid = 6375330 }}</ref>
⚫
==List of calcium channel blockers==
  
  +
−
'''Dihydropyridine calcium channel blockers''' often used to reduce systemic vascular resistance and arterial pressure, but is not used to treat angina because the vasodilation and hypotension can lead to reflex tachycardia. This CCB class is easily identified by the suffix "-pine".
  
  +
[[N-type calcium channel]]s are found in [[neuron]]s and are involved in the release of [[neurotransmitter]] at [[synapse]]s. [[Ziconotide]] is a selective blocker of these calcium channels and acts as an [[analgesic]].
  +
  +
==Classes==
  +
  +
===Dihydropyridine ===
  +
  +
'''Dihydropyridine calcium channel blockers''' are derived from the molecule [[dihydropyridine]] and often used to reduce systemic vascular resistance and arterial pressure, but are not used to treat [[angina pectoris|angina]] (with the exception of amlodipine, nicardipine, and nifedipine, which carry an indication to treat chronic stable angina as well as [[Prinzmetal's angina|vasospastic angina]]) because the vasodilation and hypotension can lead to reflex [[tachycardia]]. Dihydropiridine calcium channel blockers can worsen [[proteinuria]] in patients with [[nephropathy]].<ref>{{ cite journal | author = Remuzzi G, Scheppati A, Ruggenenti P | title = Clinical Practice. Nephropathy in Patients with Type 2 Diabetes | journal = New England Journal of Medicine | year = 2002 | volume = 346 | issue = 15 | pages = 1145–1151 | pmid = 11948275 | doi = 10.1056/NEJMcp011773 }}</ref>
  +
  +
This CCB class is easily identified by the suffix "-dipine".
 
* [[Amlodipine]] (Norvasc)
  
* [[Amlodipine]] (Norvasc)
  +
* [[Aranidipine]] (Sapresta)
  +
* [[Azelnidipine]] (Calblock)
  +
* [[Barnidipine]] (HypoCa)
  +
* [[Benidipine]] (Coniel)
  +
* [[Cilnidipine]] (Atelec, Cinalong, Siscard) Not available in US
  +
* [[Clevidipine]] (Cleviprex)
  +
* [[Isradipine]] (DynaCirc, Prescal)
  +
* [[Efonidipine]] (Landel)
 
* [[Felodipine]] (Plendil)
  
* [[Felodipine]] (Plendil)
−
* [[Nicardipine]] (Cardene, Carden SR)
 +
* [[Lacidipine]] (Motens, Lacipil)
⚫
* [[Nifedipine]] (Procardia, Adalat)
  
−
* [[Nimodipine]] (Nimotop)
  
⚫
* [[Nisoldipine]] (Sular)
  
⚫
* [[Nitrendipine]] (Cardif, Nitrepin)
  
−
* [[Lacidipine]] (Motens)
  
 
* [[Lercanidipine]] (Zanidip)
  
* [[Lercanidipine]] (Zanidip)
  +
* [[Manidipine]] (Calslot, Madipine)
  +
* [[Nicardipine]] (Cardene, Carden SR)
  ⚫
* [[Nifedipine]] (Procardia, Adalat)
  +
* [[Nilvadipine]] (Nivadil)
  +
* [[Nimodipine]] (Nimotop) This substance can pass the [[Blood brain barrier|blood-brain barrier]] and is used to prevent [[cerebral vasospasm]].
  ⚫
* [[Nisoldipine]] (Baymycard, Sular, Syscor)
  ⚫
* [[Nitrendipine]] (Cardif, Nitrepin, Baylotensin)
  +
* [[Pranidipine]] (Acalas)
  +
  +
Side effects of these drugs may include but are not limited to:
  +
* Dizziness, headache, redness in the face
  +
* Fluid buildup in the legs and ankle [[edema]]
  +
* Rapid heart rate
  +
* Slow heart rate
  +
* [[Constipation]]
  +
* [[Gingiva]]l overgrowth
  +
  +
===Non-dihydropyridine===
   
  +
====Phenylalkylamine ====
−
'''Phenylalkylamine calcium channel blockers''' are relatively selective for mycardium, reduces myocardial oxygen demand and reverses coronary vasospasm and is often used to treat angina. It has minimal vasodilatory effects compared with dihydropyridines.
 
  +
[[Image:Verapamil skeletal.svg|thumb|[[Skeletal formula]] of [[verapamil]]]]
  +
'''Phenylalkylamine calcium channel blockers''' are relatively selective for myocardium, reduce myocardial oxygen demand and reverse coronary vasospasm, and are often used to treat angina. They have minimal vasodilatory effects compared with dihydropyridines and therefore cause less reflex tachycardia, making it appealing for treatment of angina, where tachycardia can be the most significant contributor to the heart's need for oxygen. Therefore, as vasodilation is minimal with the phenylalkylamines, the major mechanism of action is causing negative inotropy. Phenylalkylamines are thought to access calcium channels from the intracellular side, although the evidence is somewhat mixed.<ref>{{ cite journal |author1=Hockerman, G.H. |author2=Peterson, B.Z. |author3=Johnson, B.D. |author4=Catterall, W.A. | title = Molecular Determinants of Drug Binding and Action on L-Type Calcium Channels | journal = Annual Review of Pharmacology and Toxicology | year = 1997 | volume = 37 | pages = 361–396 | doi = 10.1146/annurev.pharmtox.37.1.361 |pmid=9131258}}</ref>
 
* [[Verapamil]] (Calan, Isoptin)
  
* [[Verapamil]] (Calan, Isoptin)
−
* [[Gallopamil]] (D600)
 +
* [[Gallopamil]]
  +
* [[Fendiline]]
   
  +
====Benzothiazepine ====
⚫
'''Benzothiazepine calcium channel blockers''' is an intermediate class between phenylalkylamine and dihydropyridines in its selectivity for vascular calcium channels. By having both cardiac depressant and vasodilator actions, benzothiazepines are able to reduce arterial pressure without producing the same degree of reflex cardiac stimulation caused by dihydropyridines.
  
  +
[[Image:Diltiazem Structural Formulae V.1.svg|thumb|[[Structural formula]] of [[diltiazem]]]]
−
* [[Diltiazem]] (Cardizem)
  
  ⚫
'''Benzothiazepine calcium channel blockers''' belong to the [[Thiazepine|benzothiazepine]] class of compounds and are an intermediate class between phenylalkylamine and dihydropyridines in their selectivity for vascular calcium channels. By having both cardiac depressant and vasodilator actions, benzothiazepines are able to reduce arterial pressure without producing the same degree of reflex cardiac stimulation caused by dihydropyridines.
  +
* [[Diltiazem]] (Cardizem) (also used experimentally to prevent migraine)
   
  +
====Nonselective====
−
'''Other'''
  
  +
While most of the agents listed above are relatively selective, there are additional agents that are considered nonselective. These include [[mibefradil]], [[bepridil]], [[flunarizine]] ([[blood–brain barrier|BBB]] crossing), [[fluspirilene]] ([[blood–brain barrier|BBB]] crossing),<ref name="pmid7565636">{{ cite journal | author = Bezprozvanny I, Tsien RW | title = Voltage-Dependent Blockade of Diverse Types of Voltage-Gated Ca<sup>2+</sup> Channels Expressed in ''Xenopus'' Oocytes by the Ca<sup>2+</sup> Channel Antagonist Mibefradil (Ro 40-5967) | journal = Molecular Pharmacology | year = 1995 | volume = 48 | issue = 3 | pages = 540–549 | pmid = 7565636 | url = http://molpharm.aspetjournals.org/content/48/3/540.abstract }}</ref> and [[fendiline]].<ref name="pmid1755331">{{ cite journal | author = Scultéty S, Tamáskovits E | title = Effect of Ca<sup>2+</sup> Antagonists on Isolated Rabbit Detrusor Muscle | journal = Acta Physiologica Hungarica | year = 1991 | volume = 77 | issue = 3–4 | pages = 269–278 | pmid = 1755331 }}</ref>
−
* [[Menthol]] ([[mint]] [[Vegetable oil|oil]])
  
   
  +
====Ziconotide====
−
==Other drugs with similar uses==
  
  +
[[Ziconotide]], a [[peptide]] compound derived from the omega-[[conotoxin]], is a selective [[N-type calcium channel]] blocker that has potent [[analgesic]] properties that are equivalent to approximate 1,000 times that of [[morphine]]. It must be delivered via the intrathecal (directly into the cerebrospinal fluid) route via an intrathecal infusion pump.
   
  +
==Toxicity==
−
Other classes of pharmaceutical agents that have overlapping effects as calcium channel blockers include [[ACE inhibitor]]s, [[beta-blocker]]s, and nitrates.
  
  +
Mild CCB toxicity is treated with supportive care. Non-dihydropyridine CCB may produce profound toxicity and early decontamination, especially for slow release agents, is essential. For severe overdoses, treatment usually includes close monitoring of vital signs and the addition of vasopressive agents and intravenous fluids for blood pressure support. IV calcium gluconate (or calcium chloride if a central line is available) and atropine are first-line therapies. If the time of the overdose is known and presentation is within two hours of ingestion, activated charcoal, gastric lavage, and polyethylene glycol may be used to decontaminate the gut. Efforts for gut decontamination may be extended to within 8 hours of ingestion with extended release preparations.
  +
  +
Hyperinsulinemia-euglycemia (HIE) therapy has emerged as a viable form of treatment. Although the mechanism is unclear, it has been hypothesized that increased insulin mobilizes glucose from peripheral tissues to serve as an alternative fuel source for the heart (the heart mainly relies on oxidation of fatty acids). Theoretical treatment with lipid emulsion therapy has been considered in severe cases, but is not yet standard of care.
  +
  +
Caution should be taken when using verapamil with a Beta blocker due to the risk of severe bradycardia. If unsuccessful, ventricular pacing should be used.<ref>{{ cite journal | author = Buckley N, Dawson A, Whyte I | title = Calcium Channel Blockers | journal = Medicine | year = 2007 | volume = 35 | issue = 11 | pages = 599–602 | doi = 10.1016/j.mpmed.2007.08.025 }}</ref>
  +
  +
==History==
  +
Calcium channel blockers were first identified in the lab of German pharmacologist [[Albrecht Fleckenstein]] beginning in 1964.<ref>{{cite pmid|6339106}}</ref>
   
 
==See also==
  
==See also==
  +
* [[ACE inhibitor]]
−
* [[Voltage-dependent calcium channel]]
  
  +
* [[Nitrate]]
   
  +
==References==
⚫
{{Calcium channel blockers}}
  
  +
{{Reflist}}
   
  +
==External links==
−
[[Category:Calcium channel blockers|*]]
  
  +
* {{MeshName|Calcium+Channel+Blockers}}
  +
* [http://www.adalat.com Official Adalat (Nifedipine) site, Bayer]
  +
* Video - [http://www.youtube.com/watch?v=t7EWidfUIYA Calcium Channel Blockers]
   
−
{{Link FA|ar}}
 +
{{Major drug groups}}
  +
{{Channel blockers}}
  +
{{PAH rx}}
  +
{{Antiarrhythmic agents}}
  +
  +
{{DEFAULTSORT:Calcium Channel Blocker}}
  ⚫
[[Category:Calcium channel blockers|*]]
   
−
ar:حاصرات قنوات الكالسيوم
  
−
[[de:Kalziumantagonist]]
  
−
[[es:Bloqueador de canales de calcio]]
  
−
[[fr:Antagoniste du calcium]]
  
−
[[ja:カルシウム拮抗剤]]
  
−
[[nl:Calciumantagonist]]
  
−
[[pt:Bloqueador dos canais de cálcio]]
  
−
[[th:แคลเซียมแชนแนลบล็อกเกอร์]]
  
 
{{enWP|Calcium channel blocker}}
  
{{enWP|Calcium channel blocker}}

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Main article: Channel blockers

A calcium channel blocker (CCB) is a chemical that disrupts the movement of calcium (Ca2+) through calcium channels.[1] Calcium channel blockers are used as antihypertensive drugs, i.e. as medications to decrease blood pressure in patients with hypertension. CCBs are particularly effective against large vessel stiffness, one of the common causes of elevated systolic blood pressure in elderly patients.[2] Calcium channel blockers are also frequently used to alter heart rate, to prevent cerebral vasospasm, and to reduce chest pain caused by angina pectoris. One type of calcium channel blocker is used experimentally to prevent migraine, and another one is used as a powerful painkiller.

Despite their effectiveness, CCB's often have a high mortality rate over extended periods of use, and have been known to have multiple side effects.[3] Potential major risks however were mainly found to be associated with short-acting CCBs.[4]

Mechanism of action

File:Calciumkanal Förstermann.jpg

A calcium channel embedded in a cell membrane.

In the body's tissues, the concentration of calcium ions (Ca2+) outside of cells is normally about tenthousandfold higher than the concentration inside of cells. Embedded in the membrane of some cells are calcium channels. When these cells receive a certain signal, the channels open, letting calcium rush into the cell. The resulting increase in intracellular calcium has different effects in different types of cells. Calcium channel blockers prevent or reduce the opening of these channels and thereby reduce these effects.

There are several types of calcium channels, and a number of classes of calcium channel blockers, but almost all of them preferentially or exclusively block the L-type voltage-gated calcium channel.[5]

L-type calcium channels are responsible for excitation-contraction coupling of skeletal, smooth, and cardiac muscle and for hormone secretion in endocrine cells. In the heart they are also involved in the conduction of the pacemaker signals. CCBs used as medications primarily have three effects:

  • by acting on vascular smooth muscle they reduce contraction of the arteries and cause an increase in arterial diameter, a phenomenon called vasodilation (CCBs do not work on venous smooth muscle)
  • by acting on cardiac muscles (myocardium), they reduce the force of contraction of the heart
  • by slowing down the conduction of electrical activity within the heart, they slow down the heart beat.

Since blood pressure is determined by cardiac output and peripheral resistance, CCBs reduce blood pressure. With relatively low blood pressure, the afterload on the heart decreases; this decreases how hard the heart must work to eject blood into the aorta, and so the amount of oxygen required by the heart decreases accordingly. This can help ameliorate symptoms of ischaemic heart disease such as angina pectoris.

Reducing the force of contraction of the myocardium is known as the negative inotropic effect of calcium channel blockers. Slowing down the conduction of electrical activity within the heart, by blocking the calcium channel during the plateau phase of the action potential of the heart (see: cardiac action potential), results in a negative chronotropic effect, or a lowering of heart rate. This can increase the potential for heart block. The negative chronotropic effects of calcium channel blockers make them a commonly used class of agents in individuals with atrial fibrillation or flutter in whom control of the heart rate is generally a goal. Negative chronotropy can be beneficial when treating a variety of disease processes because lower heart rates represent lower cardiac oxygen requirements. Elevated heart rate can result in significantly higher "cardiac work," which can result in symptoms of angina.

The class of CCBs known as dihydropyridines mainly affect arterial vascular smooth muscle and lower blood pressure by causing vasodilation. The phenylalkylamine class of CCBs mainly affect the cells of the heart and have negative inotropic and negative chronotropic effects. The benzothiazepine class of CCBs combine effects of the other two classes.

It is because of the negative inotropic effects that the nondihydropyridine calcium channel blockers should be avoided (or used with caution) in individuals with cardiomyopathy.[6]

Unlike beta blockers, calcium channel blockers do not decrease the responsiveness of the heart to input from the sympathetic nervous system. Since moment-to-moment blood pressure regulation is carried out by the sympathetic nervous system (via the baroreceptor reflex), calcium channel blockers allow blood pressure to be maintained more effectively than do beta blockers. However, because dihydropyridine calcium channel blockers result in a decrease in blood pressure, the baroreceptor reflex often initiates a reflexive increase in sympathetic activity leading to increased heart rate and contractility.

Ionic calcium is antagonized by magnesium ions in the nervous system. Because of this, bioavailable supplements of magnesium, possibly including magnesium chloride, magnesium lactate, and magnesium aspartate, may increase or enhance the effects of calcium channel blockade.[7]

N-type calcium channels are found in neurons and are involved in the release of neurotransmitter at synapses. Ziconotide is a selective blocker of these calcium channels and acts as an analgesic.

Classes

Dihydropyridine

Dihydropyridine calcium channel blockers are derived from the molecule dihydropyridine and often used to reduce systemic vascular resistance and arterial pressure, but are not used to treat angina (with the exception of amlodipine, nicardipine, and nifedipine, which carry an indication to treat chronic stable angina as well as vasospastic angina) because the vasodilation and hypotension can lead to reflex tachycardia. Dihydropiridine calcium channel blockers can worsen proteinuria in patients with nephropathy.[8]

This CCB class is easily identified by the suffix "-dipine".

  • Amlodipine (Norvasc)
  • Aranidipine (Sapresta)
  • Azelnidipine (Calblock)
  • Barnidipine (HypoCa)
  • Benidipine (Coniel)
  • Cilnidipine (Atelec, Cinalong, Siscard) Not available in US
  • Clevidipine (Cleviprex)
  • Isradipine (DynaCirc, Prescal)
  • Efonidipine (Landel)
  • Felodipine (Plendil)
  • Lacidipine (Motens, Lacipil)
  • Lercanidipine (Zanidip)
  • Manidipine (Calslot, Madipine)
  • Nicardipine (Cardene, Carden SR)
  • Nifedipine (Procardia, Adalat)
  • Nilvadipine (Nivadil)
  • Nimodipine (Nimotop) This substance can pass the blood-brain barrier and is used to prevent cerebral vasospasm.
  • Nisoldipine (Baymycard, Sular, Syscor)
  • Nitrendipine (Cardif, Nitrepin, Baylotensin)
  • Pranidipine (Acalas)

Side effects of these drugs may include but are not limited to:

  • Dizziness, headache, redness in the face
  • Fluid buildup in the legs and ankle edema
  • Rapid heart rate
  • Slow heart rate
  • Constipation
  • Gingival overgrowth

Non-dihydropyridine

Phenylalkylamine

Verapamil skeletal

Skeletal formula of verapamil

Phenylalkylamine calcium channel blockers are relatively selective for myocardium, reduce myocardial oxygen demand and reverse coronary vasospasm, and are often used to treat angina. They have minimal vasodilatory effects compared with dihydropyridines and therefore cause less reflex tachycardia, making it appealing for treatment of angina, where tachycardia can be the most significant contributor to the heart's need for oxygen. Therefore, as vasodilation is minimal with the phenylalkylamines, the major mechanism of action is causing negative inotropy. Phenylalkylamines are thought to access calcium channels from the intracellular side, although the evidence is somewhat mixed.[9]

  • Verapamil (Calan, Isoptin)
  • Gallopamil
  • Fendiline

Benzothiazepine

File:Diltiazem Structural Formulae V.1.svg

Structural formula of diltiazem

Benzothiazepine calcium channel blockers belong to the benzothiazepine class of compounds and are an intermediate class between phenylalkylamine and dihydropyridines in their selectivity for vascular calcium channels. By having both cardiac depressant and vasodilator actions, benzothiazepines are able to reduce arterial pressure without producing the same degree of reflex cardiac stimulation caused by dihydropyridines.

  • Diltiazem (Cardizem) (also used experimentally to prevent migraine)

Nonselective

While most of the agents listed above are relatively selective, there are additional agents that are considered nonselective. These include mibefradil, bepridil, flunarizine (BBB crossing), fluspirilene (BBB crossing),[10] and fendiline.[11]

Ziconotide

Ziconotide, a peptide compound derived from the omega-conotoxin, is a selective N-type calcium channel blocker that has potent analgesic properties that are equivalent to approximate 1,000 times that of morphine. It must be delivered via the intrathecal (directly into the cerebrospinal fluid) route via an intrathecal infusion pump.

Toxicity

Mild CCB toxicity is treated with supportive care. Non-dihydropyridine CCB may produce profound toxicity and early decontamination, especially for slow release agents, is essential. For severe overdoses, treatment usually includes close monitoring of vital signs and the addition of vasopressive agents and intravenous fluids for blood pressure support. IV calcium gluconate (or calcium chloride if a central line is available) and atropine are first-line therapies. If the time of the overdose is known and presentation is within two hours of ingestion, activated charcoal, gastric lavage, and polyethylene glycol may be used to decontaminate the gut. Efforts for gut decontamination may be extended to within 8 hours of ingestion with extended release preparations.

Hyperinsulinemia-euglycemia (HIE) therapy has emerged as a viable form of treatment. Although the mechanism is unclear, it has been hypothesized that increased insulin mobilizes glucose from peripheral tissues to serve as an alternative fuel source for the heart (the heart mainly relies on oxidation of fatty acids). Theoretical treatment with lipid emulsion therapy has been considered in severe cases, but is not yet standard of care.

Caution should be taken when using verapamil with a Beta blocker due to the risk of severe bradycardia. If unsuccessful, ventricular pacing should be used.[12]

History

Calcium channel blockers were first identified in the lab of German pharmacologist Albrecht Fleckenstein beginning in 1964.[13]

See also

References

  1. ↑ Template:DorlandsDict
  2. ↑ Nelson M (2010). Drug treatment of elevated blood pressure. Australian Prescriber 33 (4): 108–112.
  3. ↑ Calcium Channel Blockers. MedicineNet.
  4. ↑ Major side effects and safety of calcium channel blockers. Chinese Medical & Biological Information.
  5. ↑ Yousef et al. (2005). The mechanism of action of calcium channel blockers in the treatment of diabetic nephropathy. Int J Diabetes & Metabolism 13: 76–82.
  6. ↑ Lehne R (2010). Pharmacology for Nursing Care, 7th, St. Louis, Missouri: Saunders Elsevier.
  7. ↑ Iseri LT, French JH (1984). Magnesium: Nature's Physiologic Calcium Blocker. American Heart Journal 108 (1): 188–193.
  8. ↑ Remuzzi G, Scheppati A, Ruggenenti P (2002). Clinical Practice. Nephropathy in Patients with Type 2 Diabetes. New England Journal of Medicine 346 (15): 1145–1151.
  9. ↑ (1997). Molecular Determinants of Drug Binding and Action on L-Type Calcium Channels. Annual Review of Pharmacology and Toxicology 37: 361–396.
  10. ↑ Bezprozvanny I, Tsien RW (1995). Voltage-Dependent Blockade of Diverse Types of Voltage-Gated Ca2+ Channels Expressed in Xenopus Oocytes by the Ca2+ Channel Antagonist Mibefradil (Ro 40-5967). Molecular Pharmacology 48 (3): 540–549.
  11. ↑ Scultéty S, Tamáskovits E (1991). Effect of Ca2+ Antagonists on Isolated Rabbit Detrusor Muscle. Acta Physiologica Hungarica 77 (3–4): 269–278.
  12. ↑ Buckley N, Dawson A, Whyte I (2007). Calcium Channel Blockers. Medicine 35 (11): 599–602.
  13. ↑ PMID 6339106 (PMID 6339106)
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