Verapamil HCl

Verapamil is an L-type calcium channel blocker of thephenylalkylamine class.

Optimization of pH-independent chronotherapeutic release of verapamil HCl from three-layer matrix tablets.[Pubmed:26276259]

Int J Pharm. 2015 Oct 15;494(1):296-303.

The aim of this work was to evaluate and optimize formulation of three-layer matrix tablets based on xanthan gum (XG) and sodium alginate for chronotherapeutic pH-independent release of Verapamil HCl (VH). Artificial neural networks (ANN) were applied in the optimization and compared with multiple linear regression (MLR). A face-centered central composite experimental design was employed with three factors (mass fraction of VH in intermediate layer, X1, and of XG in matrix former of intermediate and outer layers, X2 and X3). The prepared tablets were tested for in vitro release in 0.1 N HCl and phosphate buffer (pH 7.5), tensile strength and friability. Furthermore, swelling observation and release modeling to Weibull function and power law equation of Peppas were employed to help further understanding of release behavior and mechanism. The releases (%) in phosphate buffer (pH 7.5) at 6, 12 and 24 h were selected as responses to depict the mode of release and similarity factor (f2), between release profiles in 0.1N HCl and pH 7.5 during the first 8 h, as response of pH-independence. A desirability function combining the four responses was constructed and overall desirability values were used for the ANN and MLR modeling. Five additional checkpoint formulations, within the experimental domain, were used to validate the external predictability of the models. The constructed ANN model fitted better to the overall desirability than the MLR model (R=0.838 vs. 0.670, for the additional checkpoint formulations) and therefore, was used for prediction of formulation with optimal in vitro drug release.

Comparative release profile of sustained release matrix tablets of verapamil HCl.[Pubmed:23799207]

Int J Pharm Investig. 2013 Jan;3(1):60-5.

INTRODUCTION: Verapamil hydrochloride (VH) is a calcium channel blocking agent used in the treatment of hypertension, cardiac arrhythmia and angina pectoris. The short half-life and high frequency of administration of VH makes it a suitable candidate for designing sustained drug delivery system. The aim of the present investigation was to develop a sustained release matrix tablet of verapamil hydrochloride (VH) using ethyl cellulose, methyl cellulose, Eudragit RS 100, hydroxypropyl methylcellulose and carboxymethyl cellulose and to evaluate the drug release kinetics. MATERIALS AND METHODS: In order to achieve the required sustained release profile, the tablets were prepared by a wet granulation method using avicel PH 101 and magnesium stearate as binder and lubricant, respectively. RESULTS: The formulated tablets were characterized for pre-compression and post-compression parameters and they were in the acceptable limits. The drug release data obtained after an in vitro dissolution study was fitted to various release kinetic models in order to evaluate the release mechanism and kinetics. The criterion for selecting the best fit model was linearity (coefficient of correlation). Drug release mechanism was found to follow a complex mixture of diffusion, swelling and erosion. Furthermore, to minimize the initial burst drug release, batches were coated by using Eudragit RS100 polymer. After coating the tablets, a better release profile of the formulated tablets was expected and the release rate of the drug was compared with the marketed SR tablet of VH. CONCLUSION: The dosage form holds the potential to control the release rate of drug and extend the duration of action of a drug.

Polymer percolation threshold in HPMC extended release formulation of carbamazepine and verapamil HCl.[Pubmed:20352536]

AAPS PharmSciTech. 2010 Jun;11(2):558-62.

The principles of the percolation theory were applied to further understand and design hydroxypropyl methylcellulose (HPMC) extended release matrix tablets containing carbamazepine and Verapamil HCl. This statistical theory studies disordered or chaotic systems where the components are randomly distributed in a lattice. The application of this theory to study the hydration and drug release of hydrophilic matrices allows describing the changes in hydration and drug release kinetics of swellable matrices. The aim of this work was to study and develop extended release matrix formulations for carbamazepine and Verapamil HCl, containing hypromellose (HPMC, METHOCEL Premium K100M CR) as rate controlling polymer using the concepts of percolation theory. The knowledge of the percolation threshold of the components of the matrix formulations contributes to improve their design. First, reducing the time to market and second, avoiding to formulate in the nearby of the percolation threshold, which will result in a lower variability. Therefore these formulations will be more robust when they are prepared at industrial scale. The HPMC percolation threshold for drugs with very different water solubilities was determined and it was shown that there was no significant influence of drug solubility on the HPMC critical concentration threshold (excipient percolation threshold). This may be related to the versatility and broad functionality of the swelling hydrophilic matrices.

Bioavailability enhancement of verapamil HCl via intranasal chitosan microspheres.[Pubmed:23999035]

Eur J Pharm Sci. 2014 Jan 23;51:59-66.

Chitosan microspheres are potential drug carriers for maximizing nasal residence time, circumventing rapid mucociliary clearance and enhancing nasal absorption. The aim of the present study was to develop and characterize chitosan mucoadhesive microspheres of verapamil hydrochloride (VRP) for intranasal delivery as an alternative to oral VRP which suffers low bioavailability (20%) due to extensive first pass effect. The microspheres were produced using a spray-drying and precipitation techniques and characterized for morphology (scanning electron microscopy), particle size (laser diffraction method), drug entrapment efficiency, thermal behavior (differential scanning calorimetry) and crystallinity (X-ray diffractometric studies) as well as in vitro drug release. Bioavailability of nasal VRP microspheres was studied in rabbits and the results were compared to those obtained after nasal, oral and intravenous administration of VRP solution. Results demonstrated that the microspheres were spherical with size 21-53 mum suitable for nasal deposition. The spray-drying technique was superior over precipitation technique in providing higher VRP entrapment efficiency and smaller burst release followed by a more sustained one over 6h. The bioavailability study demonstrated that the nasal microspheres exhibited a significantly higher bioavailability (58.6%) than nasal solution of VRP (47.8%) and oral VRP solution (13%). In conclusion, the chitosan-based nasal VRP microspheres are promising for enhancing VRP bioavailability by increasing the nasal residence time and avoiding the first-pass metabolism of the drug substance.

Chemical modulators of autophagy as biological probes and potential therapeutics.[Pubmed:21164513]

Nat Chem Biol. 2011 Jan;7(1):9-17.

Autophagy is an evolutionarily conserved mechanism for protein degradation that is critical for the maintenance of homeostasis in man. Autophagy has unexpected pleiotropic functions that favor survival of the cell, including nutrient supply under starvation, cleaning of the cellular interior, defense against infection and antigen presentation. Moreover, defective autophagy is associated with a diverse range of disease states, including neurodegeneration, cancer and Crohn's disease. Here we discuss the roles of mammalian autophagy in health and disease and highlight recent advances in pharmacological manipulation of autophagic pathways as a therapeutic strategy for a variety of pathological conditions.

Effect of verapamil on intimal thickening and vascular reactivity in the collared carotid artery of the rabbit.[Pubmed:8842432]

Br J Pharmacol. 1996 Aug;118(7):1681-8.

1. Intimal thickening is a common site for atherosclerosis. Therefore, we investigated whether the calcium entry blocker verapamil (10 mg kg-1 body weight day-1, s.c.) can retard intimal thickening and changes in vascular reactivity induced by a non-occlusive, silicone collar positioned around the left carotid artery of rabbits. The contralateral carotid artery was sham-operated and served as a control. 2. Verapamil and placebo (saline 0.1 ml kg-1, day-1, s.c.) treatments were initiated 7 days before placing the collar and lasted 3 weeks. Thereafter, segments were cut from collared and sham-treated arteries for histology and isometric tension recording. 3. The intima/media (I/M ratio increased after 14 days of collar treatment, but intimal thickening was not inhibited by verapamil (I/M ratio placebo 0.31 +/- 0.07, verapamil 0.32 +/- 0.09). 4. The collar decreased the capacity to develop force, as indicated by the response to a supramaximal concentration of KCl, decreased the sensitivity (pD2) to acetylcholine (ACh) and phenylephrine (Phe), but increased the sensitivity to 5-hydroxytryamine (5-HT). 5. Although verapamil did not affect intimal thickening, it normalized the hypersensitivity to 5-HT in collared arteries. 6. The contraction to the supramaximal concentration of KCl was not affected by verapamil. Verapamil decreased the Emax of ACh, but this was only seen in collar-treated arteries. Verapamil also decreased the sensitivity to ACh and Phe, in both sham- and collar-treated arteries. 7. We conclude that verapamil, without preventing thickening of the intima, can modify collar-induced changes in vascular reactivity.

Block of P-type Ca2+ channels in freshly dissociated rat cerebellar Purkinje neurons by diltiazem and verapamil.[Pubmed:8574653]

Brain Res. 1995 Oct 9;695(1):88-91.

We investigated the effects of organic Ca2+ channel blockers, diltiazem and verapamil, on the high voltage-activated P-type Ca2+ channels in freshly isolated rat Purkinje neurons. Both diltiazem and verapamil blocked P-type Ca2+ channel current without any change in the current-voltage relation. The block was concentration-dependent. In the presence of these agents, the inactivation curve was shifted to hyperpolarizing potentials. The characteristics of block of P-type Ca2+ channels by diltiazem and verapamil are similar to that of L-type Ca2+ channels. These results indicate that both benzothiazepine and phenylalkylamine react with P-type Ca2+ channels and suggest that some structural features common to which operate in both L-type and P-type Ca2+ channels may be involved in drug binding to these channels.

Interaction of Ro 40-5967 and verapamil with the stably expressed alpha 1-subunit of the cardiac L-type calcium channel.[Pubmed:7616442]

J Pharmacol Exp Ther. 1995 Jul;274(1):54-63.

The interaction of the nondihydropyridine calcium channel antagonist Ro 40-5967 with the stably expressed class C alpha 1-subunit of the cardiac L-type calcium channel was investigated and compared with that of verapamil by using the whole cell patch clamp configuration. Both compounds blocked the Ba++ inward current. The IC50 values at a holding potential of -80 or -40 mV were 4.9 and 1.4 microM for Ro 40-5967 and 250 and 15.5 microM for verapamil. Both Ro 40-5967 and verapamil induced a partial tonic block at a holding potential of -80 mV. The block increased with high depolarization rates. Both Ro 40-5967 and verapamil shifted the steady-state inactivation curve by more than 20 mV to hyperpolarized membrane potentials and decreased the inactivation rate constant. The effect of Ro 40-5967, but not that of verapamil, was attenuated by intracellular dialysis with GTP gamma S. The affinity for verapamil was not affected by replacing Ba++ by Ca++, but was increased by the coexpression of the beta 3-subunit. These results indicate that both compounds interact with high affinity with the inactivated channel state, but may interact additionally with the open channel.