Possible requirement of phosphonate moiety for efonidipine effects on the sino-atrial node action potential

Application of Plackett-Burman and central composite designs for screening and optimization of factor influencing the chromatographic conditions of HPTLC method for quantification of efonidipine hydrochloride

We report here an analytical method for expeditious estimation of efonidipine hydrochloride in tablet formulation with statistical screening and optimization designs using NP-HPTLC. TLC silica gel 60 F254 aluminum plates and ethyl acetate to dichloromethane to triethylamine (3:2:0.5 v/v) were chosen for chromatographic separation of efonidipine hydrochloride. The Rf value for efonidipine hydrochloride turned out to be 0.35 ± 0.25 and quantitative evaluation was done at 251 nm. Plackett-Burman and face-centered central composite design (CCD) were used to obtain the most peak area and well-resolved compact band with an adequate retention factor of efonidipine hydrochloride. Plackett-Burman design at two-level with six independent variables has been employed for screening of prominent factors that affect the responses. The prominent factors have been selected and are optimized through face-centered CCD. The results obtained from face-centered CCD showed that most peak area can be obtained with development distance 8.50 cm and chamber saturation 17 min. Furthermore, the current NP-HPTLC investigation has been validated according to the ICH guidelines for accuracy, precision, sensitivity, robustness, ruggedness, and specificity. The detection and quantification limit was found that 10.41 ng and 31.57 ng, suggesting that the analysis could be accurately and precisely detected the analyte up to nanogram quantity. The current NP-HPTLC investigation is rugged, accurate, and highly sensitive and could be used for routine analysis of efonidipine hydrochloride.

Enhancement of cardiac oxidative stress by tachycardia and its critical role in cardiac hypertrophy and fibrosis

OBJECTIVE

To examine the mechanism and significance of tachycardia-induced cardiac damage, using azelnidipine, a relatively new dihydropyridine calcium channel blocker which does not increase heart rate.

METHODS

Comparing azelnidipine and amlodipine, we examined the cardiac effects and the direct effects on a sinus node/atrial preparation in stroke-prone spontaneously hypertensive rats (spSHRs). By pacing the right atrium, we examined the effect of tachycardia per se on cardiac oxidative stress. Using apocynin, a reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitor, we investigated the role of oxidative stress in cardiac remodelling.

RESULTS

Azelnidipine suppressed cardiac hypertrophy, fibrosis, NADPH oxidase and superoxide in spSHRs more potently than amlodipine, and was associated with lower heart rates than amlodipine. Azelnidipine caused a greater reduction than amlodipine in the beat rate of the sinus node/atrial preparation of spSHRs. A 10 or 20% increase in heart rate, independent of blood pressure or sympathetic nerve activity, significantly enhanced cardiac NADPH oxidase activity, superoxide and activated mitogen-activated protein kinases. Reduction of cardiac oxidative stress by apocynin led to the suppression of cardiac hypertrophy, inflammation and fibrosis in spSHRs, beyond its hypotensive effect.

CONCLUSIONS

Our work provided evidence that the increase in heart rate per se, independent of sympathetic nerve activity, enhances cardiac oxidative stress and activates mitogen-activated protein kinases, which seem to be responsible for cardiac remodelling. Azelnidipine, without causing an increase in heart rate, has the potential to be useful for the treatment of cardiac remodelling.

Pathophysiological Significance of T-type Ca2+ Channels: T-type Ca2+ Channels and Drug Development

T-type Ca(2+) channels are present in cardiovascular, neuronal, and endocrine systems; and they are now receiving attention as novel therapeutic targets. Many drugs and compounds non-specificaly block T-type Ca(2+) channels. Certain dihydropyridine compounds, such as efonidipine, have blocking activity on both L-type and T-type Ca(2+) channels which possibly underlies their excellent clinical profiles such as minimum reflex tachycardia and renal protection. Selective inhibitors of T-type Ca(2+) channels, such as non-hydrolyzable mibefradil and R(-)-efonidipine, are powerful pharmacological tools for further studies and may lead to the development of novel therapeutic strategies.

Efonidipine hydrochloride: a dual blocker of L- and T-type ca(2+) channels

T-type Ca(2+) channels have properties different from those of the L-type and are involved in cardiac pacemaking and regulation of blood flow, but not in myocardial contraction. Efonidipine is an antihypertensive and antianginal drug with dihydropyridine structure that was recently found to block both L- and T-type Ca(2+) channels. In isolated myocardial and vascular preparations, efonidipine has potent negative chronotropic and vasodilator effects but only a weak negative inotropic effect. In experimental animals and patients, reduction of blood pressure by the drug was accompanied by no or minimum reflex tachycardia leading to improvement of myocardial oxygen balance and maintenance of cardiac output. Efonidipine increased glomerular filtration rate without increasing intraglomerular pressure. By relaxing both the afferent and efferent arterioles, efonidipine markedly reduced proteinuria. Thus, efonidipine, an L- and T-type dual Ca(2+) channel blocker, appears to have an ideal profile as an antihypertensive and antianginal drug with organ-protective effects in the heart and kidney.