Effect of calcium binding protein modulators on myofibrillar MgATPase activity and cGMP-inhibitable phosphodiesterase activity from human cardiac muscle

A review of the pharmacology and clinical uses of pimobendan

OBJECTIVE

To review the pharmacology, research developments, and clinical uses of pimobendan

DATA SOURCES

Original research articles and clinical studies from 1984 to August 2011.

VETERINARY DATA SYNTHESIS

Pimobendan is approved for use in dogs for the treatment of congestive heart failure (CHF) secondary to chronic valvular heart disease (CVHD) and dilated cardiomyopathy (DCM). Expert-based veterinary guidelines recommend the use of pimobendan in the management of acute, hospital-based therapy for patients with CHF attributable to CVHD.

CONCLUSIONS

The use of pimobendan, an inodilator with phosphodiesterase 3 (PDE3) inhibitory and calcium-sensitizing properties, is regarded as a component of the standard of care in the management of dogs with CHF secondary to both DCM and CVHD. Further studies are warranted to confirm the safety and efficacy of pimobendan for the off-label use of this drug in asymptomatic CVHD, pulmonary arterial hypertension, asymptomatic myocardial diseases, CHF from all other causes and in cats with CHF.

Effects of pimobendan, its active metabolite UD-CG 212, and milrinone on isolated blood vessels

The effects of pimobendan, 2-(4-hydroxy-phenyl)-5-(5-methyl-3-oxo-4,5-dihydo-2H-6-pyridazinyl ) benzimidazole (UD-CG 212), and milrinone were investigated on isometric contraction of vascular preparations in rats and guinea-pigs. The drugs dose dependently relaxed aortic, carotid and femoral arterial and mesenteric venous preparations precontracted with KCl or norepinephrine. The rank order of potency (negative log EC50 value) for these drugs was dependent upon the sources of the preparations and stimulants used. The relaxation response to milrinone was reversible, that to UD-CG 212 was poorly reversible, and that to pimobendan was intermediate. Relaxation responses to cromakalim were inhibited by 0.1 microM glibenclamide, whereas those to pimobendan, UD-CG 212 and milrinone were inhibited by glibenclamide only at doses as high as 10-30 microM. The drugs potentiated the relaxation response to isoproterenol but not glyceryl trinitrate, and noncompetitively inhibited arterial contractions accompanied by voltage-dependent Ca2+ influxes. It is suggested that the drugs are potent vasorelaxants, acting directly on vascular smooth muscle and that the vasorelaxant effects are mediated through cyclic AMP-dependent mechanisms.