Tuesday, 2 December 2014



CAS: 74150-27-9
 UD-CG 115; UD-CG 115 BS; 2-(4-methoxyphenyl)-5(6)-(5-methyl-3-oxo-4,5-dihydro-2H-6-pyridazinyl)benzimidazole
  1. 4,5-dihydro-6-(2-(4-methoxyphenyl)-1H-benzimidazole-5-yl)-5-methyl-3(2H)-pyridazinone
  2. pimobendan
  3. pimobendane
  4. UD CG 115
  5. UD-CG 115
  6. UD-CG115
MF: C19H18N4O2
MW: 334.37
Percent Composition: C 68.25%, H 5.43%, N 16.76%, O 9.57%
Boehringer Ingelheim (Originator)
Derivative Type: Hydrochloride
CAS : 77469-98-8
MF: C19H18N4O2.HCl
MW: 370.83
Percent Composition: C 61.54%, H 5.16%, N 15.11%, O 8.63%, Cl 9.56%
Prop: Crystals from methanol and ethereal HCl, mp 311°(dec). LD50 orally in mice: ~600 mg/kg (Austel, 1982).
MP: mp 311°(dec)
Toxicity data: LD50 orally in mice: ~600 mg/kg (Austel, 1982)
Therap-Cat: Cardiotonic.
Pimobendan (INN is a veterinary medication manufactured by Boehringer Ingelheim under the trade names Vetmedin and Acardi) or pimobendane. It is a calcium sensitizer with positive inotropic and vasodilator effects. It is also a selective inhibitor ofphosphodiesterase III (PDE3).
Pimobendan is used in the management of heart failure in dogs, most commonly caused by myxomatous mitral valve disease (also known as endocardiosis), or dilated cardiomyopathy.[1] Research has shown that pimobendan increases survival time and improves quality of life in patients with congestive heart failure secondary to mitral valve disease when compared with benazepril, anangiotensin-converting-enzyme (ACE) inhibitor.[2] Under the trade name Acardi, it is available for human use in Japan.[3]

Mechanism of action

Pimobendan is a positive inotrope. It sensitizes and increases the binding efficiency 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 andafterload (decreases the failing heart’s workload).


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 feces. Pimobendan is 90–95% bound to plasma proteins in circulation. This has implications in patients suffering from low blood protein levels (hypoproteinemia/hypoalbuminemia) and with patients that are on concurrent therapies that are also highly protein bound.


Pimobendan is often used in combination with three other drugs to palliate dogs with heart disease and reduce clinical signs of disease. These are:
Other drugs may also be used as required to manage certain arrhythmias that are often associated with heart disease.


Pimobendan can be synthesized beginning with anisoyl chloride.
Pimobendan synthesis:[4]
The cyclization of methyl 3- [4- (4-methoxybenzoylamino) -3-nitrobenzoyl] butyrate (I) with hydrazine hydrate in refluxing acetic acid gives 4,5-dihydro-6- [4- (4-methoxybenzoylamino) -3- nitrobenzoyl] -5-methylpyridazin-3 (2H) -one (II), which is reduced with H2 over Pd / C in ethanol yielding the corresponding amino derivative (III). Finally, this compound is cyclized in refluxing acetic acid.


  1.  Gordon SG, Miller MW, Saunders AB (2006). “Pimobendan in heart failure therapy—a silver bullet?”J Am Anim Hosp Assoc 42 (2): 90–3. PMID 16527909.
  2.  Häggström J, Boswood A, O’Grady M, et al. (July 2008). “Effect of Pimobendan or Benazepril Hydrochloride on Survival Times in Dogs with Congestive Heart Failure Caused by Naturally Occurring Myxomatous Mitral Valve Disease: The QUEST Study”. J. Vet. Intern. Med. 22 (5): 1124–35. doi:10.1111/j.1939-1676.2008.0150.xPMID 18638016.
  3.  “Kusuri-no-Shiori Drug Information Sheet”. RAD-AR Council, Japan. April 2005. Retrieved 2008-08-06.
  4.  Nicolas, C.; Verny, M.; Maurizis, J. C.; Payard, M.; Faurie, M. (1986). “Synthesis of 14C-bucromarone succinate and hydrochloride”. Journal of Labelled Compounds and Radiopharmaceuticals 23 (8): 837. doi:10.1002/jlcr.2580230806edit

Further reading

External links

Pimobendan skeletal.svg
Systematic (IUPAC) name
Clinical data
AHFS/Drugs.comInternational Drug Names
Legal status
  • ℞ Prescription only
Pharmacokinetic data
Bioavailability60 to 65%
Half-life0.4 hours
ExcretionIn feces
CAS number74150-27-9 Yes
ATCvet codeQC01CE90
PubChemCID 4823
KEGGD01133 Yes
Chemical data
Mol. mass334.37 g/mol
References: Positive inotropic agent. Prepn: V. Austel et al., DE 2837161eidem, US 4361563 (1980, 1982 both to Thomae).
Cardiovascular effects: J. C. A. von Meel, Arzneim.-Forsch. 35, 284 (1985); P. D. Verdouw et al., Eur. J. Pharmacol.126, 21 (1986). Comparison of enantiomer activity: K. Fujino et al., J. Pharmacol. Exp. Ther. 247, 519 (1988).
Clinical trial in congestive heart failure: F. Hagemeijer, Am. Heart J. 122, 517 (1991); S. D. Katz et al., ibid. 123, 95 (1992).

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