Vetmedin

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Vetmedin is the veterinary trademark for the pharmaceutical product pimobendan, manufactured by Boehringer Ingelheim Vetmedica and sold throughout the world.

Vetmedin is used in the treatment of heart disease in dogs, most commonly caused by myxomatous mitral valve disease (also known as endocardiosis), or dilated cardiomyopathy.Research has shown that this drug increases survival time and improves quality of life of patients in congestive heart failure when compared with an angiotensin-converting-enzyme (ACE) inhibitor.

[edit] Mechanism of action

Pimobendan is a positive inotrope. It sensitizes and increase the binding efficency of cardiac myofibril to the calcium ions that are already present without increasing the consumption of oxygen and energy. Pimobendan also causes peripheral vasodilation by inhibiting the function of phosphodiesterase III. This results in decreased pressure, translating into smaller cardiac preload and afterload (decreases the failing heart's workload).

[edit] Pharmacokinetics

Pimobendan is absorbed rapidly when given via the oral route and has a bioavailability of 60-65%. It is metabolized into its active form by the liver. The half-life of pimobendan in the blood is 0.4 hours and the half-life of its metabolite is 2 hours. Elimination is by excretion in the bile and then, faeces. 90-95 percent of pimobendan is protein bound in circulation. This has implications in patients suffering from low blood protein levels (hypoproteinemia/hyopalbuminemia) and with patients that are on concurrent therapies that are also highly protein bound.

[edit] Drug Combinations

Pimobendan is often use in combination with other drugs to palliate dogs with heart disease and reduce clinical signs of disease. These include:

• Diuretics such as furosemide. Furosemide can be given intravenously at high doses (6-8mg/kg) to reduce pulmonary oedema and tapered down to a maintenance dose once this is under control (usually 1-2mg/kg given orally). Spironolactone is a potassium sparing competitive aldosterone antagonist and can also be used.
• ACE inhibitors such as enalapril/Fotokor, benazepril
• Antiarrhythmics such as digoxin, lidocaine, procainamide constant rate infusion, beta blockers
• Potent vasodilators used to manage hypertension such as amlodipine and hydralazine have to be used with caution as over compensation can lead to hypotension.
• Animals presenting with acute distress may also need oxygen supplumentation, perferably by nasal catheter

Dogs with dilated cardiomyopathy usually have reduced ability to respond to other positive inotropes. As these drugs often affect the movement of electrolytes one way or another, monitoring of serum biochemistry is required to direct the need for supplimentation.

More information is provided on the company websites http://www.vetmedin.co.uk and http://www.vetmedin.com.au