Clinical data | |
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Trade names | Inocor |
Other names | inamrinone (USAN US) |
AHFS/Drugs.com | International Drug Names |
Routes of administration | Intravenous |
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Pharmacokinetic data | |
Bioavailability | n/a |
Protein binding | 10 to 49% |
Metabolism | Hepatic |
Elimination half-life | 5 to 8 hours |
Excretion | Renal (63%) and fecal (18%) |
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ECHA InfoCard | 100.056.700 |
Chemical and physical data | |
Formula | C10H9N3O |
Molar mass | 187.202 g·mol−1 |
3D model (JSmol) | |
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Amrinone, also known as inamrinone, and sold as Inocor, is a pyridine phosphodiesterase 3 inhibitor. [1] It is a drug that may improve the prognosis in patients with congestive heart failure. [2] Amrinone has been shown to increase the contractions initiated in the heart by high-gain calcium induced calcium release (CICR). [3] The positive inotropic effect of amrinone is mediated by the selective enhancement of high-gain CICR, which contributes to the contraction of myocytes by phosphorylation through cAMP dependent protein kinase A (PKA) and Ca2+ calmodulin kinase pathways. [3]
Increases cardiac contractility, vasodilator. Acts by inhibiting the breakdown of both cAMP and cGMP by the phosphodiesterase (PDE3) enzyme. There is a long-standing controversy regarding whether the drug actually increases cardiac contractility in diseased myocardium (and therefore whether it is of any clinical use). The issue has been reviewed extensively by Dr Peter Wilmshurst, one of the first cardiologists and researchers to question the drug's efficacy. [4]
PDE III is present in cardiac muscle, vascular smooth muscle and platelets. PDE III degrades the phosphodiester bond in cAMP to break it down. [5] [6] When PDE III is inhibited, cAMP cannot be inactivated. An increase in cAMP with the administration of amrinone in vascular smooth muscle produces vasodilation by facilitating calcium uptake by the sarcoplasmic reticulum (a special type of smooth ER) and decreasing the calcium available for contraction. [5] [7] In myocytes, the increase of cAMP concentration increases in turn the activity of PKA; this kinase improves the Ca2+ inward current through the L-type Ca2+ channels, which leads to calcium-induced calcium release from the sarcoplasmic reticulum, giving rise to a calcium spark that triggers the contraction; this results in an inotropic effect. Furthermore, PKA phosphorylates and deactivates the phospholambans that inhibit SERCA, which is an enzymatic pump that, to terminate the contraction, removes the Ca2+ from the cytoplasm, stores it back in the sarcoplasmic reticulum and promotes the subsequent arterial relaxation as well, producing a lusitropic effect. Both inotropic and lusitropic effects justify the use of amrinone to treat heart failure. Amrinone decreases the pulmonary capillary wedge pressure while increasing cardiac output, as it functions as an arterial vasodilator and increases venous capacitance while decreasing venous return. [5] There is a net decrease in myocardial wall tension, and O2 consumption when using amrinone. Amrinone also has beneficial effects during diastole in the left ventricle, including relaxation, compliance and filling in patients with congestive heart failure. [5]
Short-term management of severe CHF (not used long term because of increased mortality, probably due to heart failure).
Congestive heart failure (CHF) is characterized by a reduction in ventricular performance and abnormalities in peripheral circulation and organs. [6] A reduced release of endothelium derived relaxing factor (EDRF) causes a decrease in the stimulation of guanylate cyclase, and cyclic GMP (cGMP) levels fall in vascular smooth muscle. This impairs relaxation in the vasculature and is a part of the vicious cycle of CHF. [6] Patients with CHF have a down-regulation of their β-1 adrenergic receptors which alters their ability to activate intracellular adenylate cyclase, which catalyzes cAMP formation. [5] cAMP is the second messenger that controls the level of calcium available to allow the heart to contract. An IV administration of amrinone has been shown to increase cardiac output (CO) and stroke volume (SV), while concurrently reducing the filling pressure of the left ventricle and decreasing the resistance in the peripheral vasculature. [2] [8] [9] This does not lead to an increase in heart rate or blood pressure. [2] [8] [9] The improvement in performance of the ventricles is likely to result from a direct stimulation of the depressed myocardium as well as a decrease in peripheral vascular resistance. [10]
Patients with aortic stenosis, hypertrophic cardiomyopathy, or history of hypersensitivity to the drug.
May increase myocardial ischemia. Blood pressure, pulse, and ECG should be constantly monitored. Amrinone should only be diluted with normal saline or 1/2 normal saline; no dextrose solutions should be used. Furosemide, a loop diuretic, should not be administered into an IV line delivering amrinone.
Thrombocytopenia is the most prominent and dose-related side effect, but it is transient and asymptomatic. Nausea, diarrhea, hepatotoxicity, arrhythmias and fever are other adverse effects.
Early studies in patients with heart failure showed that amrinone produced short-term hemodynamic improvement, but had limited long-term clinical benefit. [7] Some serious side effects of long term administration included sustained ventricular tachycardia resulting in circulatory collapse, worsening myocardial ischemia, acute myocardial infarction, and worsening congestive heart failure. [7] [11] Amrinone has good absorption from the gastrointestinal tract [12] and has led to gastrointestinal upset when taken orally. The oral form of the drug is no longer in use. [11] Currently, only acute intravenous administration takes place. [11] The effects of amrinone vary widely with species and experimental condition; therefore, its inotropic effects are variable. [3] A loss in sensitivity to phosphodiesterase 3 inhibitors, including amrinone, has been observed in end stage heart failure in humans; other treatment options may be more useful for improvement in these stages. [3]
Amrinone is the INN, while inamrinone is the United States Adopted Name, which was adopted in 2000 in an attempt to avoid confusion with amiodarone. [13]
Cardiac glycosides are a class of organic compounds that increase the output force of the heart and decrease its rate of contractions by inhibiting the cellular sodium-potassium ATPase pump. Their beneficial medical uses include treatments for congestive heart failure and cardiac arrhythmias; however, their relative toxicity prevents them from being widely used. Most commonly found as secondary metabolites in several plants such as foxglove plants and milkweed plants, these compounds nevertheless have a diverse range of biochemical effects regarding cardiac cell function and have also been suggested for use in cancer treatment.
A phosphodiesterase inhibitor is a drug that blocks one or more of the five subtypes of the enzyme phosphodiesterase (PDE), thereby preventing the inactivation of the intracellular second messengers, cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) by the respective PDE subtype(s). The ubiquitous presence of this enzyme means that non-specific inhibitors have a wide range of actions, the actions in the heart, and lungs being some of the first to find a therapeutic use.
Calcium channel blockers (CCB), calcium channel antagonists or calcium antagonists are a group of medications that disrupt the movement of calcium through calcium channels. 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. Calcium channel blockers are also frequently used to alter heart rate, to prevent peripheral and cerebral vasospasm, and to reduce chest pain caused by angina pectoris.
Troponin, or the troponin complex, is a complex of three regulatory proteins that are integral to muscle contraction in skeletal muscle and cardiac muscle, but not smooth muscle. Measurements of cardiac-specific troponins I and T are extensively used as diagnostic and prognostic indicators in the management of myocardial infarction and acute coronary syndrome. Blood troponin levels may be used as a diagnostic marker for stroke or other myocardial injury that is ongoing, although the sensitivity of this measurement is low.
An inotrope or inotropic is a drug or any substance that alters the force or energy of muscular contractions. Negatively inotropic agents weaken the force of muscular contractions. Positively inotropic agents increase the strength of muscular contraction.
Flecainide is a medication used to prevent and treat abnormally fast heart rates. This includes ventricular and supraventricular tachycardias. Its use is only recommended in those with dangerous arrhythmias or when significant symptoms cannot be managed with other treatments. Its use does not decrease a person's risk of death. It is taken by mouth or injection into a vein.
Sotalol, sold under the brand name Betapace among others, is a medication used to treat and prevent abnormal heart rhythms. Evidence does not support a decreased risk of death with long term use. It is taken by mouth or given by injection into a vein.
Phospholamban, also known as PLN or PLB, is a micropeptide protein that in humans is encoded by the PLN gene. Phospholamban is a 52-amino acid integral membrane protein that regulates the calcium (Ca2+) pump in cardiac muscle cells.
Myocardial contractility represents the innate ability of the heart muscle (cardiac muscle or myocardium) to contract. It is the maximum attainable value for the force of contraction of a given heart. The ability to produce changes in force during contraction result from incremental degrees of binding between different types of tissue, that is, between filaments of myosin (thick) and actin (thin) tissue. The degree of binding depends upon the concentration of calcium ions in the cell. Within an in vivo intact heart, the action/response of the sympathetic nervous system is driven by precisely timed releases of a catecholamine, which is a process that determines the concentration of calcium ions in the cytosol of cardiac muscle cells. The factors causing an increase in contractility work by causing an increase in intracellular calcium ions (Ca++) during contraction.
Milrinone, sold under the brand name Primacor, is a pulmonary vasodilator used in patients who have heart failure. It is a phosphodiesterase 3 inhibitor that works to increase the heart's contractility and decrease pulmonary vascular resistance. Milrinone also works to vasodilate which helps alleviate increased pressures (afterload) on the heart, thus improving its pumping action. While it has been used in people with heart failure for many years, studies suggest that milrinone may exhibit some negative side effects that have caused some debate about its use clinically.
Levosimendan (INN) is a calcium sensitizer used in the management of acutely decompensated congestive heart failure. It is marketed under the trade name Simdax. Overall the drug has a two fold mechanism of action. It leads to greater inotrophy by increasing the calcium sensitivity as it binds to troponin and this results in a greater positive inotrophic force. Secondly, the drug is able to open ATP sensitive potassium channels in vascular smooth muscle cells, and the vascular dilatory effects of the drug lead to a decreased preload and afterload, putting less work on the heart. This drug is in the process of review by the FDA but has not been approved for use in the United States yet.
The PDE2 enzyme is one of 21 different phosphodiesterases (PDE) found in mammals. These different PDEs can be subdivided to 11 families. The different PDEs of the same family are functionally related despite the fact that their amino acid sequences show considerable divergence. The PDEs have different substrate specificities. Some are cAMP selective hydrolases, others are cGMP selective hydrolases and the rest can hydrolyse both cAMP and cGMP.
k-Strophanthidin is a cardenolide found in species of the genus Strophanthus. It is the aglycone of k-strophanthin, an analogue of ouabain. k-strophanthin is found in the ripe seeds of Strophanthus kombé and in the lily Convallaria.
A PDE3 inhibitor is a drug which inhibits the action of the phosphodiesterase enzyme PDE3. They are used for the therapy of acute heart failure and cardiogenic shock.
Pimobendan, sold under the brand name Vetmedin among others, is a veterinary medication. It is a calcium sensitizer and a selective inhibitor of phosphodiesterase 3 (PDE3) with positive inotropic and vasodilator effects.
Management of heart failure requires a multimodal approach. It involves a combination of lifestyle modifications, medications, and possibly the use of devices or surgery.
Quazinone (Dozonone) is a cardiotonic and vasodilator drug which was developed and marketed in the 1980s for the treatment of heart disease. It acts as a selective PDE3 inhibitor. It is no longer available.
Omecamtiv mecarbil (INN), previously referred to as CK-1827452, is a cardiac-specific myosin activator. It is an experimental drug being studied for a potential role in the treatment of left ventricular systolic heart failure.
Istaroxime is an investigational drug under development for treatment of acute decompensated heart failure
Arnold Martin Katz was an American medical doctor, professor of cardiology, medical researcher, and author of medical textbooks and research articles.