Use of the co-grinding method to enhance the dissolution behavior of a poorly water-soluble drug: generation of solvent-free drug-polymer solid dispersions.
(11/49)
The solid dispersion (SD) technique is the most effective method for improving the dissolution rate of poorly water-soluble drugs. In the present work, SDs of the Ca2+ channel blocker dipfluzine (DF) with polyvinylpyrrolidone K30 (PVP) and poloxamer 188 (PLXM) were prepared by the powder solid co-grinding method under a solvent-free condition. The properties of all SDs and physical mixtures were investigated by X-ray diffraction, Fourier-transform infrared, differential scanning calorimetry, scanning electron microscopy, dissolution test, and particles size determination. Eutectic compounds were produced between the DF and PLXM matrix during the co-grinding process, whereas glass suspension formed in the SDs with PVP carrier. Hydrogen bond formation was not observed between DF and carriers and DF was microcrystalline state in the PVP and PLXM matrices. The solubility of DF in different concentration of carriers at 25, 31, and 37 degrees C was investigated; the values obtained were used to calculate the thermodynamic parameters of interaction between DF and carriers. The Gibbs free energy (DeltarGtheta) values were negative, indicating the spontaneous nature of dispersing DF into the carriers. Moreover, entropy is the drive force when DF disperses into the matrix of PVP, while, enthalpy-driven dispersing encounters in the PLXM carrier. All the SDs of DF/carriers showed a considerably higher dissolution rate than pure DF and the corresponding physical mixtures. The cumulative dissolution rate at 10 min of the SD with a 1 : 3 DF/carrier ratio increased 5.1-fold for PVP and 5.5-fold for PLXM. (+info)
RS-WebPredictor: a server for predicting CYP-mediated sites of metabolism on drug-like molecules.
(12/49)
Acute toxicity of dipfluzine and its effects on isolated vascular smooth muscle.
(14/49)
Dipfluzine (Dip) is a new derivative of cinnarizine (Cin) first developed by Department of Chemistry, Beijing University. Dip showed a dose-dependently inhibitory effect on both KCl- and NE-induced contraction in the rabbit aortic rings. It was more effective in suppressing the contractile response evoked by KCl than that by NE. Dip also inhibited the KCl-induced contraction in porcine basilar, coronary and radial arteries. Their pD2' values were 5.7 +/- 0.6, 5.4 +/- 0.4 and 4.6 +/- 0.5 respectively. The selectivity of Dip for vasodilation was proved by higher pD2' value of the basilar artery than that of the coronary and radial arteries, and this selectivity of Dip was more significant than that of Cin. The acute iv LD50 of Dip and Cin in mice were 37 and 36 mg/kg, respectively. (+info)
Variable, voltage-dependent, blocking effects of nitrendipine, verapamil, diltiazem, cinnarizine and cadmium on adrenomedullary secretion.
(15/49)
1. Catecholamine release from cat adrenal glands perfused at a high rate (4 ml min-1) at 37 degrees C with modified Krebs solutions lacking Ca and containing 1.2 mM K (hyperpolarizing solution) or 118 mM K (depolarizing solution) was triggered by 10-s pulses of Ca (0.5 mM) in the presence of 118 mM K. Hyperpolarized glands released 1280 +/- 135 ng per pulse and depolarized glands 831 +/- 98 ng per pulse (n = 29). 2. While the dihydropyridine Ca channel blocker nitrendipine inhibited secretion in hyperpolarized glands with an IC50 of 214 nM, in depolarizing conditions the drug was much more potent (IC50 = 0.99 nM). In contrast, the inorganic Ca channel blocker cadmium inhibited secretion with the same potency both in hyperpolarized or depolarized glands. 3. Cinnarizine, diltiazem and verapamil exhibited intermediate degrees of voltage-dependence in blocking secretion. The IC50 ratios between hyperpolarized and depolarized glands were 215, 36, 19, 8 and 0.76 respectively for nitrendipine, cinnarizine, diltiazem, verapamil and cadmium. Because the experimental design (strong depolarization in the absence of Ca) favours the highest opening probability of Ca channels, it seems that these drugs bind preferentially to their receptors when these channels are in their open state. 4. Variable voltage-dependent effects of the five Ca channel blockers on adrenomedullary catecholamine release suggests different sites and mechanisms of action on, or near L-type Ca channels in chromaffin cells. In addition, these findings might help to explain why these drugs exhibit tissue selectivity and why they act differently in normal polarized as compared to ischaemic depolarized cells. (+info)
Functional, behavioral, and histological changes induced by transient global cerebral ischemia in rats: effects of cinnarizine and flunarizine.
(16/49)
Temporary cerebral ischemia (15 min) produced by "four-vessel occlusion" in the rat causes neurological disorders, changes in behavior (locomotor hyperactivity), and neuronal damage in the neocortex, striatum, and especially the CA1 zone of the hippocampus. We have studied the effects of two calcium overload blockers, flunarizine (50 mg/kg p.o. twice a day) and cinnarizine (100 mg/kg p.o. twice a day), on these alterations. Cinnarizine markedly improved the functional abnormalities of ischemia but had little or no effect upon the neuronal damage. In contrast, flunarizine provided far greater neuronal protection but with less obvious effects upon behavioral parameters. However, there was evidence of sedation 2 h after treating animals with this dose of flunarizine that might have masked any positive effect of the drug on behavior. We conclude that under the present experimental conditions, there is no correlation between the early and late behavioral changes observed following a temporary cerebral ischemic episode and the histological damage observed in certain vulnerable neurons, particularly in the hippocampus, 72 h after the insult. (+info)