Amlodipine for hypertension – how does it work?
Amlodipine, sold under the brand name Norvasc among others, belongs to a class of medications called calcium channel blockers.1 Amlodipine is commonly prescribed to treat hypertension and a variety of conditions related to the cardiovascular system. How does amlodipine work, what is it used for, and what are the common side effects?
Amlodipine, which is available as amlodipine besylate, is a prescription medication approved by the Food and Drug Administration (FDA) to treat a variety of conditions. Amlodipine is commonly prescribed to treat high blood pressure (hypertension) as it can help lower blood pressure and in turn potentially decrease the risk of adverse cardiovascular events such as heart attacks and stroke.2,3 It is also prescribed to treat angina, which is chest pain caused by a lack of blood flow to the heart.3
Amlodipine is also prescribed off-label to treat a variety of complications associated with coronary artery disease , as amlodipine treatment may be associated with a reduced rate of carotid arterial plaques (atherosclerosis) and reduced occurrence of heart attacks in people with coronary artery disease.4
Amlodipine is a commonly prescribed calcium channel blocker because it has a long half-life of between 30 and 50 hours; this makes it convenient for many patients because they generally only have to take a pill once daily.1
How was amlodipine discovered?
Calcium channel blockers were studied in the 1960s for their effectiveness in dilating coronary blood vessels; this was based on older evidence that suggested that calcium played an important role in muscle contraction.5 Some examples of earlier calcium channel blockers developed in the 1960s and early 1970s include flunarizine, verapamil, nifedipine, and diltiazem.5
When amlodipine was developed in the early 1980s, it showed interesting pharmacological properties that made it stand out from other calcium channel blockers. It was slow-releasing, which was ideal for some hypertensive patients as it didn’t cause significant acute drops in blood pressure.6 The FDA approved amlodipine as a treatment in 1987.1
How does amlodipine work?
Constriction of the blood vessels, or vasoconstriction, can facilitate an increase in blood pressure because there is less intravascular space for blood to flow through. Vasoconstriction occurs when the smooth muscles in the blood vessels contract, and this is initiated by enzymes. These enzymes stimulate smooth muscle contraction when an influx of calcium enters the muscle cells through calcium channels.6
Amlodipine works by blocking these calcium channels, which reduces the amount of calcium that enters the smooth muscle cells.1 This helps reduce the extent to which the blood vessels constrict, leading to vasodilation and a decrease in blood pressure.
Amlodipine primarily inhibits the channels in vascular smooth muscle cells rather than cardiac muscle cells.7 As a result, its effects are selective towards vasodilation rather than impacting the function of other types of muscle cells.
Side effects of amlodipine
Although the side effects of amlodipine are often relatively mild compared to some other medications, patients taking amlodipine may report side effects including headache, fluid retention (edema) in the ankles, drowsiness, dizziness, skin flushing, and nausea.3 Call your doctor for medical advice about side effects if you are taking amlodipine and are concerned about your symptoms.
There are a few rare historical instances of calcium channel blockers being linked to liver disease and injury; however, this is very rare.8 A full recovery from this is generally expected, and symptoms generally subside within four to eight weeks of stopping amlodipine treatment.9
Some people may have conditions that could render amlodipine harmful; for example, people with an allergy to amlodipine should not take amlodipine as it could potentially initiate an allergic reaction. Some evidence suggests that amlodipine treatment could potentially trigger adverse reactions such as ventricular dysfunction in patients with severe aortic stenosis, which is narrowing of the aortic valve.1 However, recent research has shown conflicting results, so more research is needed.10
It is unknown whether amlodipine is safe during pregnancy; however, it is not generally prescribed for pregnant women given that the risk cannot be ruled out.11
Amlodipine could potentially have some drug interactions, including prescription medications such as certain antibiotics and antifungals, other antihypertensive medications, some antiretroviral medications, certain antiepileptics, certain immunosuppressants, and large doses of simvastatin.12 For this reason, it is important to tell your doctor about any medications and supplements that you are taking.
This article is not medical advice, and it is not intended to prescribe, diagnose, or promote specific treatments for any condition.
References
1. Bulsara, K.G., Cassagnol, M. (2020, November 4). Amlodipine. StatPearls [Internet]. Accessed 2021, March 18, from https://www.ncbi.nlm.nih.gov/books/NBK519508/
2. Steffen, H. (2004). Use of calcium channel antagonists for the treatment of hypertension in the elderly. Drugs Aging 21(9): 565-581. Doi: 10.2165/00002512-200421090-00002.
3. RxList Professional (2020, October 27). Norvasc. RxList. Accessed 2021, March 19, from https://www.rxlist.com/norvasc-drug.htm#description
4. Preston Mason, R. (2002, December). Mechanisms of plaque stabilization for the dihydropyridine calcium channel blocker amlodipine: review of the evidence. Atherosclerosis 165(2): 191-199. Doi: 10.1016/s0021-9150(01)00729-8.
5. Godfraind, T. (2017, May 29). Discovery and development of calcium channel blockers. Front Pharmacol 8(286). Doi: 10.3389/fpharm.2017.00286.
6. Burges, R.A., Dodd, M.G. (1990). Amlodipine. Cardiovascular Drug Reviews 8(1): 25-44. Accessed online from https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1527-3466.1990.tb00427.x
7. Ananchenko, G., Lewis, J., et al (2012). Chapter 2 – Amlodipine Besylate. Profiles of Drug Substances, Excipients, and related methodology 37: 31-77. Doi: 10.1016/B978-0-12-397200-0.00002-7.
8. National Institute of Diabetes and Digestive and Kidney Diseases (2017, January 11). Calcium Channel Blockers. LiverTox: Clinical and Research Information on Drug-Induced Liver Injury [Internet]. Accessed online 2021, March 19, from https://www.ncbi.nlm.nih.gov/books/NBK548577/
9. National Institute of Diabetes and Digestive and Kidney Diseases (2016, March 1). Amlodipine. LiverTox: Clinical and Research Information on Drug-Induced Liver Injury [Internet]. Accessed online 2021, March 19, from https://www.ncbi.nlm.nih.gov/books/NBK548585/
10. Kang, T.S., Park, S. (2018, June 22). Antihypertensive treatment in severe aortic stenosis. J Cardiovasc Imaging 26(2): 45-53. Doi: 10.4250/jcvi.2018.26.e9
11. Mito, A., Murashima, A., et al (2019, July 26). Safety of amlodipine in early pregnancy. Journal of the American Heart Association 2019(8). Doi: 10.1161/JAHA.119.012093
12. NHS UK (2018, December 18). Amlodipine. NHS, United Kingdom. Accessed 2021, March 20, from https://www.nhs.uk/medicines/amlodipine/
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