Amlodipine is used in the management of hypertension (high blood pressure)[17] and coronary artery disease in people with either stable angina (where chest pain occurs mostly after physical or emotional stress)[18]orvasospastic angina (where it occurs in cycles) and without heart failure. It can be used as either monotherapy or combination therapy for the management of hypertension or coronary artery disease. Amlodipine can be administered to adults and to children 6–17 years of age.[7] Calcium channel blockers, including amlodipine, may provide greater protection against stroke than beta blockers.[19][20] Evidence from two meta-analyses has reported no significant difference between calcium channel blockers, ACE inhibitors, diuretics[21][19] and angiotensin receptor blockers[21] in stroke protection while one 2015 meta-analysis has suggested that calcium channel blockers offer greater protection against stroke than other classes of antihypertensive.[20]
Amlodipine along with other calcium channel blockers are considered the first choice in the pharmacological management of Raynaud's phenomenon.[22]
Amlodipine can be given as a combination therapy with a variety of medications:[10][23]
Amlodipine/atorvastatin, where amlodipine is given for hypertension or CAD and atorvastatin prevents cardiovascular events, or if the person also has high cholesterol.
The only absolute contraindication to amlodipine is an allergy to amlodipine or any other dihydropyridines.[7]
Other situations occur, however, where amlodipine generally should not be used. In patients with cardiogenic shock, where the heart's ventricles are not able to pump enough blood, calcium channel blockers exacerbate the situation by preventing the flow of calcium ions into cardiac cells, which is required for the heart to pump.[24] While use in patients with aortic stenosis (narrowing of the aorta where it meets the left ventricle) since it does not inhibit the ventricle's function is generally safe, it can still cause collapse in cases of severe stenosis.[25]Inunstable angina (excluding variant angina), amlodipine can cause a reflex increase in cardiac contractility (how hard the ventricles squeeze) and heart rate, which together increase the demand for oxygen by the heart itself.[26] Patients with severe hypotension can have their low blood pressure exacerbated, and patients in heart failure can get pulmonary edema. Those with impaired liver function are unable to metabolize amlodipine to its full extent, giving it a longer half-life than typical.[7][6]
Amlodipine's safety in pregnancy has not been established, although reproductive toxicity at high doses is known. Whether amlodipine enters the milk of breastfeeding mothers is also unknown.[7][6]
Those who have heart failure, or recently had a heart attack, should take amlodipine with caution.[27]
Some common dose-dependent adverse effects of amlodipine include vasodilatory effects, peripheral edema, dizziness, palpitations, and flushing.[7][28] Peripheral edema (fluid accumulation in the tissues) occurs at rate of 10.8% at a 10-mg dose (versus 0.6% for placebos), and is three times more likely in women than in men.[7] It causes more dilation in the arterioles and precapillary vessels than the postcapillary vessels and venules. The increased dilation allows for more blood, which is unable to push through to the relatively constricted postcapillary venules and vessels; the pressure causes much of the plasma to move into the interstitial space.[29] Amlodipine-association edema can be avoided by adding ACE inhibitors or angiotensin II receptor antagonist.[10] Of the other dose-dependent side effects, palpitations (4.5% at 10 mg vs. 0.6% in placebos) and flushing (2.6% vs. 0%) occurred more often in women; dizziness (3.4% vs. 1.5%) had no sex bias.[7]
Amlodipine-associated gingival overgrowth is a relatively common side effect with exposure to amlodipine.[32] Poor dental health and buildup of dental plaque are risk factors.[32]
Amlodipine may increase the risk of worsening angina or acute myocardial infarction, especially in those with severe obstructive coronary artery disease, upon dosage initiation or increase. However, depending on the situation, amlodipine inhibits constriction and restores blood flow in coronary arteries as a result of its acting directly on vascular smooth muscle, causing a reduction in peripheral vascular resistance and a consequent reduction in blood pressure.[10]
Although rare,[34] amlodipine overdose toxicity can result in widening of blood vessels, severe low blood pressure, and fast heart rate.[35] Toxicity is generally managed with fluid replacement[36] monitoring ECG results, vital signs, respiratory system function, glucose levels, kidney function, electrolyte levels, and urine output. Vasopressors are also administered when low blood pressure is not alleviated by fluid resuscitation.[7][35]
Several drugs interact with amlodipine to increase its levels in the body. CYP3A inhibitors, by nature of inhibiting the enzyme that metabolizes amlodipine, CYP3A4, are one such class of drugs. Others include the calcium-channel blocker diltiazem, the antibiotic clarithromycin, and possibly some antifungals.[7] Amlodipine causes several drugs to increase in levels, including cyclosporine, simvastatin, and tacrolimus (the increase in the last one being more likely in people with CYP3A5*3 genetic polymorphisms).[37] When more than 20 mg of simvastatin, a lipid-lowering agent, are given with amlodipine, the risk of myopathy increases.[38] The FDA issued a warning to limit simvastatin to a maximum dose of 20 mg if taken with amlodipine based on evidence from the SEARCH trial.[39] Giving amlodipine with Viagra increases the risk of hypotension.[7][10]
Amlodipine is a long-acting calcium channel antagonist that selectively inhibits calcium ion influx across cell membranes.[40] It targets L-type calcium channels in muscle cells and N-type calcium channels in the central nervous system which are involved in nociceptive signalling and pain perception.[41][42] Amlodipine has an inhibitory effect on calcium influx in smooth muscle cells to inhibit contraction.[citation needed]
Amlodipine ends up significantly reducing total vascular resistance without decreasing cardiac output expressed by pressure-rate product and cardiac contractability in comparison with verapamil, a non-dihydropyridine.[43] In turn, following treatment lasting a month, with amlodipine, cardiac output is significantly enhanced.[43] Unlike verapamil which has efficacy in moderation of emotional arousal and reduces cardiac load without lowering cardiac output demands, amlodipine increases the cardiac output response concomitantly with increased functional cardiac load.[43]
Amlodipine is an angioselective calcium channel blocker and inhibits the movement of calcium ions into vascular smooth muscle cells and cardiac muscle cells which inhibits the contraction of cardiac muscle and vascular smooth muscle cells. Amlodipine inhibits calcium ion influx across cell membranes, with a greater effect on vascular smooth muscle cells. This causes vasodilation and a reduction in peripheral vascular resistance, thus lowering blood pressure. Its effects on cardiac muscle also prevent excessive constriction in the coronary arteries.[10]
Negative inotropic effects can be detected in vitro, but such effects have not been seen in intact animals at therapeutic doses. Among the two stereoisomers [R(+), S(–)], the (–) isomer has been reported to be more active than the (+) isomer.[44] Serum calcium concentration is not affected by amlodipine. And it specifically inhibits the currents of L-typeCav1.3 channels in the zona glomerulosa of the adrenal gland.[45][46]
The mechanisms by which amlodipine relieves angina are:
Stable angina: amlodipine reduces the total peripheral resistance (afterload) against which the heart works and reduces the rate pressure product, thereby lowering myocardial oxygen demand, at any given level of exercise.[47]
Amlodipine and one of its major metabolites: The nitrogen-containing ring is oxidized, and two of the side chains are hydrolyzed.[50]
Amlodipine has been studied in healthy volunteers following oral administration of 14C-labelled drug.[51] Amlodipine is well absorbed by the oral route with a mean oral bioavailability around 60%; the half-life of amlodipine is about 30 h to 50 h, and steady-state plasma concentrations are achieved after 7 to 8 days of daily dosing. In the blood it has high plasma protein binding of 97.5%.[41] Its long half-life and high bioavailability are largely in part of its high pKa (8.6); it is ionized at physiological pH, and thus can strongly attract proteins.[7] It is slowly metabolized in the liver by CYP3A4, with its amine group being oxidized and its side ester chain being hydrolyzed, resulting in an inactive pyridine metabolite.[52] Renal elimination is the major route of excretion with about 60% of an administered dose recovered in urine, largely as inactive pyridine metabolites. However, renal impairment does not significantly influence amlodipine elimination.[53] 20-25% of the drug is excreted in the faeces.[54]
Pfizer's patent protection on Norvasc lasted until 2007; total patent expiration occurred later in 2007.[55] A number of generic versions are available. In the United Kingdom, tablets of amlodipine from different suppliers may contain different salts. The strength of the tablets is expressed in terms of amlodipine base, i.e., without the salts. Tablets containing different salts are therefore considered interchangeable. Fixed-dose combination of amlodipine and perindopril, an angiotensin converting enzyme inhibitor are also available.[56]
Amlodipine is most often used to treat systemic hypertension in both cats and dogs.[60] In cats, it is the first line of treatment due to its efficacy and few side effects.[61] Systemic hypertension in cats is usually secondary to another abnormality, such as chronic kidney disease, and so amlodipine is most often administered to cats with kidney disease.[62] While amlodipine is used in dogs with systemic hypertension, it is not as efficacious. Amlodipine is also used to treat congestive heart failure due to mitral valve regurgitation in dogs.[63] By decreasing resistance to forward flow in the systemic circulation it results in a decrease in regurgitant flow into the left atrium.[64] Similarly, it can be used on dogs and cats with left-to-right shunting lesions such as ventricular septal defect to reduce the shunt. Side effects are rare in cats. In dogs, the primary side effect is gingival hyperplasia.[65]
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^Boden WE (2012). Goldman's Cecil Medicine (24 ed.). Saunders. ISBN978-1-4377-1604-7. Archived from the original on 26 August 2023. Retrieved 26 August 2023. Dihydropyridine calcium-channel blockers (e.g., amlodipine, 5 to 10 mg orally per day) are preferred in patients with Prinzmetal's angina.
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^ abMukete BN, Cassidy M, Ferdinand KC, Le Jemtel TH (August 2015). "Long-Term Anti-Hypertensive Therapy and Stroke Prevention: A Meta-Analysis". American Journal of Cardiovascular Drugs. 15 (4): 243–257. doi:10.1007/s40256-015-0129-0. PMID26055616. S2CID33792903.
^Delgado-Montero A, Zamorano JL (December 2012). "Atorvastatin calcium plus amlodipine for the treatment of hypertension". Expert Opinion on Pharmacotherapy. 13 (18): 2673–2685. doi:10.1517/14656566.2012.742064. PMID23140185. S2CID43250258.
^Kastner A, Stuart KV, Montesano G, De Moraes CG, Kang JH, Wiggs JL, et al. (October 2023). "Calcium Channel Blocker Use and Associated Glaucoma and Related Traits Among UK Biobank Participants". JAMA Ophthalmology. 141 (10): 956–964. doi:10.1001/jamaophthalmol.2023.3877. PMC 10485742. PMID37676684.
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^ abcNazzaro P, Manzari M, Merlo M, Triggiani R, Scarano AM, Lasciarrea A, et al. (September 1995). "Antihypertensive treatment with verapamil and amlodipine. Their effect on the functional autonomic and cardiovascular stress responses". European Heart Journal. 16 (9): 1277–1284. doi:10.1093/oxfordjournals.eurheartj.a061086. PMID8582392.
^Zhu Y, Wang F, Li Q, Zhu M, Du A, Tang W, et al. (February 2014). "Amlodipine metabolism in human liver microsomes and roles of CYP3A4/5 in the dihydropyridine dehydrogenation". Drug Metabolism and Disposition. 42 (2): 245–249. doi:10.1124/dmd.113.055400. PMID24301608. S2CID329321.
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^Papich MG (2007). "Amlodipine Besylate". Saunders Handbook of Veterinary Drugs (2nd ed.). St. Louis, Mo: Saunders/Elsevier. pp. 26–27. ISBN9781416028888.
^Henik RA, Snyder PS, Volk LM (28 August 2014). "Treatment of systemic hypertension in cats with amlodipine besylate". Journal of the American Animal Hospital Association. 33 (3): 226–234. doi:10.5326/15473317-33-3-226. PMID9138233.
