Brands

Vetmedin, Acardi

Availability

• Chewable Tablets: 1.25 mg, 2.5 mg, & 5 mg
• Capsules and Suspension: variety of strengths can be obtained from compounding pharmacies, online, through prescription from veterinarian (e.g., Wedgewood Pharmacy, based in New Jersey: https://www.wedgewoodpharmacy.com/items/pimobendan-oral-suspension.html).

Pharmacology

Pimobendan, a benzimidazole-pyridazinone derivative, is a non-sympathomimetic, non-glycoside drug that has both positive inotropic and vasodilative actions. This dual mechanism of action consists of an increase in intracellular calcium sensitivity without increasing calcium levels of cardiac myofilaments (i.e., that which composes muscle fibrils of the heart), and inhibits phosphodiesterase (Type III) allowing vasodilation. Pimobendan enhances cardiac contractility without increasing myocardial oxygen or energy consumption.

Basically this means that the heart’s pumping action is improved and that the blood vessels are able to dilate and carry blood to and from the heart easier; thereby reducing the heart’s workload.

In dogs, following oral administration of Vetmedin® capsules, the absolute bioavailability of the active principle is 60-63%. The mean plasma protein binding is 93%, and plasma elimination half-life of pimobendan is approximately 30 minutes.

The main active metabolite elimination half-life of pimobendan is approximately 2 hours, and most of the drug is found to be eliminated in the feces.

Laboratory studies in rats have not shown there to be any evidence of teratogenic or fetotoxicity. However, these studies have shown signs of maternotoxicity and embryotoxicity at high doses, and have shown that pimobendan is excreted into breast milk.

The safety of using this drug in pregnant or nursing animals has not been determined and should therefore only be used in those animals where the benefit outweighs the risk.

In vitro studies done on rat tissue have shown that pimobendan increases glucose-induced insulin release from pancreatic β-cells in a dose dependent manner.

Pimobendan is metabolized in the liver; therefore, it is recommended that care should be taken when administering to animals suffering from hepatic insufficiency.

Indications

Used in mild, moderate, or severe congestive heart failure due to venous congestion and dilated cardiomyopathy.

Drug Interactions or Contraindications

• Pimobendan should not be given in cases of hypertrophic cardiomyopathy, aortic stenosis, or any other condition where increasing cardiac output is deemed inappropriate for functional or anatomical reasons.
• The concurrent use of pimobendan with a beta-blocker (e.g., atenolol) or calcium channel blocker (e.g., amlodipine, verapamil, Cardizem), may reduce or weaken the positive inotropic action of pimobendan.

Adverse Reactions

CNS: lethargy, weakness, ataxia

CV: changes in heart rate, rhythm, irritability of the heart (e.g., tachyarrhythmia’s, ventricular tachycardia) and mechanics of the heart. Petechial hemorrhage on mucous membranes may occur but resolves upon discontinuation of treatment.

Resp: Dyspnea

GI: decreased appetite, polydipsia, diarrhea

GU:  polyuria, azotemia

Dosage Recommendations

0.2 mg/kg to 0.4 mg/kg, PO, q12hr  ^{34, 35, 41, 42, 44}

Considerations

• Pimobendan can be administered safely with diuretics, ace inhibitors, and digoxin.
• Depending upon response to treatment with pimobendan dosing will be life long.
• Although the recommendation is to give the drug an hour before feeding, due to decreased absorption in the presence of food, this seems to pertain more to the aqueous solution form of pimobendan rather than in its chewable form.
• Store in a dry area, at room temperature, away from light.

References

1. Cardisure Flavoured 10 mg tablets for dogs. (2011, August 1). Veterinary Medicines Directorate. Retrieved June 5, 2013, from www.vmd.defra.gov.uk/ProductInformationDatabase/SPC_Documents/SPC_321906.doc
2. FDA approves new drug for heart failure in dogs. (2007, May 16). US Food and Drug Administration. Retrieved June 5, 2013, from www.fda.gov/animalveterinary/newsevents/cvmupdates/ucm048033.htm
3. Vetmedin (pimobendan) chewable tablets. (2007, July 1). Boehringer Ingelheim Vetmedica, Inc.. Retrieved June 5, 2013, from www.vetmedin.com/Vetmedin%20Insert_6-07.pdf
4. Vetmedin: dual-acting inodilator. (n.d.). Boehringer Ingelheim Vetmedica, Inc.. Retrieved June 5, 2013, from http://www.vetmedin.com/about_vetmedin/dual_acting_inodilator.aspx