Pimobendan (

INN Inns are generally establishments or buildings where travelers can seek lodging, and usually, food and drink. Inns are typically located in the country or along a highway; before the advent of motorized transportation they also provided accommo ...

, or pimobendane; tradenames Vetmedin, Acardi) is a veterinary medication. It is a calcium sensitizer and a selective inhibitor of phosphodiesterase 3 (PDE3) with positive

inotropic An inotrope is an agent 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. The term ''inotro ...

and vasodilator effects. Pimobendan is used in the management of heart failure in dogs, most commonly caused by myxomatous mitral valve disease (also previously known as endocardiosis), or

dilated cardiomyopathy Dilated cardiomyopathy (DCM) is a condition in which the heart becomes enlarged and cannot pump blood effectively. Symptoms vary from none to feeling tired, leg swelling, and shortness of breath. It may also result in chest pain or fainting. Co ...

. Research has shown that as a monotherapy, pimobendan increases survival time and improves quality of life in canine patients with

congestive heart failure Heart failure (HF), also known as congestive heart failure (CHF), is a syndrome, a group of signs and symptoms caused by an impairment of the heart's blood pumping function. Symptoms typically include shortness of breath, excessive fatigue, ...

secondary to mitral valve disease when compared with

benazepril Benazepril, sold under the brand name Lotensin among others, is a medication used to treat high blood pressure, heart failure, and diabetic kidney disease. It is a reasonable initial treatment for high blood pressure. It is taken by mouth. Ver ...

, an ACE inhibitor. However, in clinical practice, it is often used in conjunction with an ACE inhibitor like

enalapril Enalapril, sold under the brand name Vasotec among others, is an ACE inhibitor medication used to treat high blood pressure, diabetic kidney disease, and heart failure. For heart failure, it is generally used with a diuretic, such as furose ...

or benazepril. Under the trade name Acardi, it is available for human use in Japan.

Mechanism of action

Pimobendan is a positive

inotrope An inotrope is an agent 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. The term ''inot ...

(increases myocardial contractility). It sensitizes and increases the binding efficiency of cardiac troponin in the

myofibril A myofibril (also known as a muscle fibril or sarcostyle) is a basic rod-like organelle of a muscle cell. Skeletal muscles are composed of long, tubular cells known as muscle fibers, and these cells contain many chains of myofibrils. Each myo ...

to the calcium ions that are already present in systole. In normal hearts it increases the consumption of oxygen and energy to the same degree as dobutamine but in diseased hearts it may not. Pimobendan also causes peripheral

vasodilation Vasodilation is the widening of blood vessels. It results from relaxation of smooth muscle cells within the vessel walls, in particular in the large veins, large arteries, and smaller arterioles. The process is the opposite of vasoconstrictio ...

by inhibiting the function of PDE3. This results in decreased resistance to blood flow through systemic arterioles, which decreases afterload (decreases the failing heart's workload) and reduces the amount of mitral regurgitation.

Pharmacokinetics

Pimobendan is absorbed rapidly when given via the oral route and has a

bioavailability In pharmacology, bioavailability is a subcategory of absorption and is the fraction (%) of an administered drug that reaches the systemic circulation. By definition, when a medication is administered intravenously, its bioavailability is 100%. Ho ...

of 60-65%. Bioavailability is markedly decreased when ingested with food. It is metabolized into an active metabolite (desmethylpimobendan) by the liver. The parent compound, pimobendan, is a potent calcium sensitizer while desmethylpimobendan is a more potent phosphodiesterase III inhibitor.Hanzlicek AS1, Gehring R, Kukanich B, Kukanich KS, Borgarelli M, Smee N, Olson EE, Margiocco M. "Pharmacokinetics of oral pimobendan in healthy cats." ''J Vet Cardiol''. 2012 Dec;14(4):489-96. The

half-life Half-life (symbol ) is the time required for a quantity (of substance) to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable at ...

of pimobendan in the blood is 0.4 hours, and the half-life of its metabolite is two hours. Elimination is by excretion in the bile and then feces. Pimobendan is 90–95% bound to plasma proteins in circulation. This may have implications in patients with low blood protein levels (

hypoproteinemia Hypoproteinemia is a condition where there is an abnormally low level of protein in the blood. There are several causes that all result in edema once serum protein levels fall below a certain threshold. Causes # Nutritional hypoproteinemia is due ...

hypoalbuminemia Hypoalbuminemia (or hypoalbuminaemia) is a medical sign in which the level of albumin in the blood is low. This can be due to decreased production in the liver, increased loss in the gastrointestinal tract or kidneys, increased use in the body, or ...

) and in patients that are on concurrent therapies that are also highly protein bound.

Combinations

Pimobendan is often used in combination with three other drugs to palliate dogs with heart failure (pulmonary edema, pleural effusion, ascites). These are: *

Furosemide Furosemide is a loop diuretic medication used to treat fluid build-up due to heart failure, liver scarring, or kidney disease. It may also be used for the treatment of high blood pressure. It can be taken by injection into a vein or by m ...

, a diuretic, to reduce edema and effusion. *

Spironolactone Spironolactone, sold under the brand name Aldactone among others, is a medication that is primarily used to treat fluid build-up due to heart failure, liver scarring, or kidney disease. It is also used in the treatment of high blood press ...

, an aldosterone antagonist. This has two actions, firstly, as a

potassium-sparing diuretic Potassium-sparing diuretics refers to drugs that cause diuresis without causing potassium loss in the urine. They are typically used as an adjunct in management of hypertension, cirrhosis, and congestive heart failure. The steroidal aldostero ...

, although its diuretic properties are small compared with those of furosemide. Secondly, it reduces aldosterone-mediated myocardial fibrosis, possibly slowing the progression of heart disease. *An ACE inhibitor, often

(trade name Enacard) or

(Fortekor). These drugs inhibit the action of angiotensin-converting enzyme, producing a balanced vasodilation, along with other potentially favorable effects. Other drugs may also be used as required to manage certain

arrhythmias Arrhythmias, also known as cardiac arrhythmias, heart arrhythmias, or dysrhythmias, are irregularities in the heartbeat, including when it is too fast or too slow. A resting heart rate that is too fast – above 100 beats per minute in adults ...

that are often associated with heart disease.

Synthesis

The reaction between p-anisoyl chloride 00-07-2(1) an
CID:20516917
(2) gives 4- -[(4-Methoxybenzoyl)amino3-nitrophenyl.html" ;"title="4-Methoxybenzoyl)amino.html" ;"title="-[(4-Methoxybenzoyl)amino">-[(4-Methoxybenzoyl)amino3-nitrophenyl">4-Methoxybenzoyl)amino.html" ;"title="-[(4-Methoxybenzoyl)amino">-[(4-Methoxybenzoyl)amino3-nitrophenyl3-methyl-4-oxobutanoic acid
CID:20516902
(3). The reaction of this with hydrazine gives 5-methyl-6-[3-nitro-4-(4-methoxy-benzoylamino)-phenyl]-3-oxo-4,5-dihydro-2H-pyridazine [74149-73-8]. Catalytic hydrogenation reduces the nitro group giving [74149-74-9] (4). cyclization of the resulting ortho amino amide by means of a strong acid leads to the formation of the corresponding benzimidazole. There is thus obtained pimobendan (5).

References

External links

Official Vetmedin Product Website
{{Vasodilators used in cardiac diseases Benzimidazoles Lactams PDE3 inhibitors Calcium sensitizers Inotropic agents Vasodilators Pyridazines Phenol ethers Dog medications