Evaluation of the role of ATP-binding cassette transporters as a defence mechanism against temephos in populations of Aedes aegypti

The role of ATP-binding cassette (ABC) transporters in the efflux of the insecticide, temephos, was assessed in the larvae of Aedes aegypti. Bioassays were conducted using mosquito populations that were either susceptible or resistant to temephos by exposure to insecticide alone or in combination with sublethal doses of the ABC transporter inhibitor, verapamil (30, 35 and 40 μM). The best result in the series was obtained with the addition of verapamil (40 μM), which led to a 2x increase in the toxicity of temephos, suggesting that ABC transporters may be partially involved in conferring resistance to the populations evaluated.

Programmed delivery of verapamil hydrochloride from tablet in a capsule device

The aim of the present work was to develop a programmed drug delivery system which would be able to release the drug after 6 h of lag time by use of hydrophilic polymers. The capsule body was made impermeable by use of formaldehyde vapor treatment, while the cap was untreated. The capsule was filled with two layered tablets (tablet-in-capsule), followed by a sodium bicarbonate:citric acid mixture (SBCM) and lactose as bulking agent. Sodium alginate, chitosan, HPMC K15 and chitosan:sodium alginate complex (CSAC) were used as the rate modulating layer. Through combined use of HPMC K15 and adjusting the ratio of CSAC, the desired lag time of 6 h was obtained. The effect of the bulking agents on the lag time were also studied and it was found that the lag time was decreased with higher amounts of lactose, and delayed dissolution and decreased lag time was observed at higher amount of effervescent mixture.

O objetivo do presente trabalho foi desenvolver sistema de liberação programada de cloridrato de verapamil capaz de liberação imediata do fármaco após 6 h de intervalo de tempo usando polímeros hidrofílicos. O corpo da cápsula foi impermeabilizado por tratamento de vapor de formaldeído, enquanto a tampa não foi submetida ao tratamento. Dois comprimidos foram inseridos na cápsula (comprimidos em cápsula) seguido de mistura de bicarbonato de sódio: ácido cítrico e lactose, utilizados como excipientes. O alginato de sódio, a quitosana, o HPMC K15 e o complexo quitosana:alginato de sódio foram utilizados para modular a razão de liberação do fármaco. A combinação entre o HPMC K15 e o ajuste da proporção do complexo quitosana:alginato de sódio permitiu a liberação do fármaco após 6 h. O efeito dos excipientes na liberação do fármaco foi também avaliado. Verificou-se que o tempo de latência foi reduzido na presença de maior quantidade de lactose, enquanto o menor tempo foi observado empregando maior concentração da mistura efervescente.

An HPLC-UV method for the measurement of permeability of marker drugs in the Caco-2 cell assay

The Caco-2 cell line has been used as a model to predict the in vitro permeability of the human intestinal barrier. The predictive potential of the assay relies on an appropriate in-house validation of the method. The objective of the present study was to develop a single HPLC-UV method for the identification and quantitation of marker drugs and to determine the suitability of the Caco-2 cell permeability assay. A simple chromatographic method was developed for the simultaneous determination of both passively (propranolol, carbamazepine, acyclovir, and hydrochlorothiazide) and actively transported drugs (vinblastine and verapamil). Separation was achieved on a C18 column with step-gradient elution (acetonitrile and aqueous solution of ammonium acetate, pH 3.0) at a flow rate of 1.0 mL/min and UV detection at 275 nm during the total run time of 35 min. The method was validated and found to be specific, linear, precise, and accurate. This chromatographic system can be readily used on a routine basis and its utilization can be extended to other permeability models. The results obtained in the Caco-2 bi-directional transport experiments confirmed the validity of the assay, given that high and low permeability profiles were identified, and P-glycoprotein functionality was established.

Preparation, characterization and release of verapamil hydrochloride from polycaprolactone/ acrylic acid [PCL/AA] hydrogels

In this study pH sensitive, biocompatible and controlled released hydrgels were prepared and their localized drug delivery effect was analyzed. Polycaprolactone and acrylic acid [PCL/AA] were reacted by free radical polymerization and developed inter penetrating polymeric network [IPN] hydrogels. Benzylperoxide was used as initiator and N, N methylenebisacrylamide [NNMBisAm] was employed as a cross-linking agent. Different concentrations of monomer, polymer and cross-linking agent were used and the reaction parameters were optimized. The obtained PCL/AA hydrogels were fully characterized by Fourier transform infrared spectroscopy [FT-IR], scanning electron microscopy [SEM], and thermogravimetric analysis [TGA] that determined the polymer structure, its morphology and strength respectively. Verapamil, a calcium channel blocker was loaded by incubation of polymerization method. Controlled release Verapamil hydrogel was developed due to its low solubility; low permeability and having very short half life of 1.2-2 h. The dynamic swelling, equilibrium swelling and drug release were carried out in a buffer solution of pH 1.2, 4.5 and 6.8. Concentration of Acrylic acid showed direct, while Polycaprolactone inverse relation to swelling and drug release due to their hydrophilic and hydrophobic nature respectively. Cross-linking agent also had the contrary effect on swelling. Diffusion coefficient [D] of hydrogels was determined by using Flory-Rehner theory. Drug release and swelling data were analyzed by different kinetic models, like Zero order, First order, Higuchi, Korsmeyer's and Peppas. The release and diffusion was best described by the first order kinetics where n value was <0.5 for all the formulations indicating Fickian drug release mechanism

Development and evaluation of floating microspheres of verapamil hydrochloride

The present study involves preparation and evaluation of floating microspheres of verapamil hydrochloride for improving the drug bioavailability by prolongation of gastric residence time. Cellulose acetate, acrycoat S100 and eudragit S100 microspheres loaded with verapamil hydrochloride were prepared by solvent diffusion-evaporation method. The microspheres had smooth surfaces, with free-flowing and good-packing properties. The yield of the microspheres was up to 70.51 percent and cellulose acetate microspheres entrapped the maximum amount of the drug. Scanning electron microscopy confirmed their hollow structures with sizes in the range 251.80 to 350.75 mm. The prepared microspheres exhibited prolonged drug release and remained buoyant for more than 12 h. Radiographic images of dog stomach revealed that cellulose acetate microspheres loaded with barium sulphate floated on the gastric fluid for about 3.2 h. In vitro release studies demonstrated non-Fickian diffusion of drug from the microspheres.

O presente estudo envolve a preparação e a avaliação de microesferas flutuantes de cloridrato de verapamil para o melhoramento da biodisponibilidade do fármaco por meio do prolongamento do tempo de residência gástrica. Prepararam-se, por meio do método de difusão-evaporação de solvente, microesferas de acetato de celulose, acrycoat S100 e eudragit S100 carregadas com cloridrato de verapamil. As microesferas apresentaram superfícies regulares, com propriedades de fluxo livre e de bom empacotamento. O rendimento das microesferas foi superior a 70,51 por cento e as microesferas de acetato de celulose captaram a quantidade máxima do fármaco. Microscopia eletrônica de varredura confirmou as cavidades em suas estruturas, com tamanhos na faixa de 251,80 a 350,75 mm. As microesferas preparadas apresentaram liberação prolongada do fármaco e permaneceram flutuantes por mais que 12 h. Imagens radiográficas do estômago de cão revelaram que as esferas de acetato de celulose carregadas com sulfato de bário flutuaram no fluido gástrico por, aproximadamente, 3,2 h. Estudos de liberação in vitro demonstraram difusão não-Fickiana dos fármacos das microesferas.

Angina inestable: los calcibloqueantes sin betabloqueantes no previenen la recurrencia de la angina, los procedimientos intervencionistas, ni la insuficiencia cardíaca / Calcium channel bloquer agentes, not associated to betabloquers, do not prevent recurrent angina, further invasive procedures or pump failure in patients hospitalized for unstable angina

Antecentes. Los calciantagonistas (CA) deberían ser eficaces en reducir la mortalidad y el infarto (IAM) no fatal en la angina inestable (AI). Se ha demostrado que los CA proporcionan alivio sintomático y mejor evolución. Objetivo. Investigar si los CA en la AI disminuyen la muerte y el IAM no fatal, previenen la recurrencia de la angina y mejoran la evolución. Material y métodos. Análisis en la base de datos del estudio ENAI (Enalapril en la Angina Inestable) que sigue durante 7 días a 1022 pacientes con AI. Indicación de betabloqueantes (BB) y CA a criterio de los participantes. Resultados. La angina recurrente y los procedimientos invasivos no son diferentes en la AI previamente tratada con CA (RR 1,02; IC95 0,74 - 1,40; P 0,8958). En 1022 pacientes los eventos secundarios aumentan en los no tratados (53,3 por ciento en 629) en relación a los tratados con CA cuando se asocian a los BB (46,7 por ciento en 392; RR 1,39; IC95 1,19 - 1,62; P 0,00003) Para Diltiazem-BB los eventos secundarios disminuyen desde un 61,3 por ciento al 38,7 por ciento (RR 1,74; ; IC95 1,39 - 2,18; P 0,0000), similar con otros CA-BB. Reducen los eventos secundarios del 66 por ciento al 34 por ciento en el grupo con SD del ST/ST normal (RR del 1,92; IC95 1,05 - 3,51; P 0,0335). Conclusiones. La indicación de CA sin BB en AI no disminuye los eventos isquémicos secundarios ni el desarrollo de insuficiencia cardíaca. Indicados en AI con SD del ST.

Efeito de tratamentos anti-hipertensivos no coração de ratos com inibição crônica da síntese do óxido nítrico: biometria, alometria e estereologia / Antihypertensive drugs treatment effects in rats heart with inhibition of nitric oxide synthesis: biometry, allometry and stereology

Alterações estruturais do miocárdio devidas á inibição da síntese de óxido nítrico e concomitante tratamento com três drogras anti-hipertensivas foram estudadas quantitativamente após de 40 dias do tratamento. Cinco grupo de 10 ratos: Controle, L-NAME, espironolactona, enalapril e verapamil foram estudados. L-NAME foi administrado na dose de 50 mg/kg/dia na água do bebedouro. No 41§ dia de experimentação os ratos foram anestesiados, pesados e sacrificados. A pressão arterial da cauda (PAC) aumentou 76 por cento e 16 por cento nos grupos L-NAME e espironolactona, respectivamente, em comparação ao grupo de controle. A espironolactona, o enalapril e o verapamil foram eficientes em reduzir a PAC nos respectivos grupos (a espironolactona foi menos eficiente na redução da PAC). O volume do coração (VC) foi maior no grupo L-NAME que nos outros grupos, mas não foi diferente entre os grupos L-NAME e espironolactona. O ventrículo esquerdo foi o responsável pelas mudanças no VC. A relação entre o VC e a massa corporal (MC) não foi significativa entre os grupos L-NAME e espironolactona. Porém, esta relação foi alométrica nos grupos controle, enalapril e verapamil. No grupo controle o VC teve uma tendência alométrica positiva em relação a MC, mas nos trupos enalapril e verapamil esta tendência foi alométrica negativa. A hipertrofia cardíaca nestes animais foi prevenida mais eficazmente pelo uso do enalapril e do verapamil do que pela espironolactona. A inibição da síntese do ON provocou modificações no miocárdio e as drogas anti-hipertensivas foram eficientes na prevenção das modificações causadas pela hipertensão e a estereologia quantificou estas alteraçoes. Foram determinadas as densidades de volume dos cardiomiócitos (Vv[c]), intertício cardíaco (Vv[i]), densidade de superfície de cardiomiócitos (Sv[c]) e área transversão média dos cardiomiócitos (A[c]). Ocorreu hipertrofia dos cardiomiócitos vista através do aumento da A[c] que foi 30 por centro maior no grupo L-NAME, 13 por cento nos grupos espironolactona e enalapril. Aos 40 dias ocorrei diminuilão do Vv[c] e aumento do Vv[i] nos animais L-NAME (15 por centro e 24 por centro respectivamente)...

Effect of a new triazinoaminopiperidine derivative [S9788] on the binding of vinceistine to and 1-acid glycoprotein: implication in multidrug resistance phenomena

Multidrug resistance [MDR] was circumvented by a large number of compounds including verapamil and a newly synthesized triazinoaminopiperidine derivative S9788 [Servier 9788]. S9788 was found to overcome multidrug resistance both in vitro and in vivo. The mode of action of these chemosensitizers is thought to involve interaction on P-glycoprotein, a membrane-bound efflux transport protein for cytotoxic drugs. On the other hand, verapamil binds strongly to alpha 1-acid glycoprotein [AGP] in serum or solutions and AGP can modulate the chemosensitizing action of verapamil in MDR in vitro. The interaction of S9788 with [3H] vincristine was measured at binding sites on alpha 1-acid glycoprotein in vitro using equilibrium dialysis [Dianorm] and clinically relevant concentrations of ligands and protein

Measurement of plasma verapamil levels by high-performance liquid chromatography

1. We have developed an alternative procedure for the measurement of verapamil levels in human plasma by reverse-phase high performance liquid chromatography with fluorimetric detection. 2. Prior to assay, plasma is submitted to a double extraction procedure, using first n-heptane in alkaline medium and then an acid phosphate buffer. Flecainide, a compound not related to verapamil, is used as internal standard. Mean recoveries of 70 and 63 per cent were obtained for verapamil and flecainide, respectively. 3. The sensitivity (5 ng/ml), reproducibility (inter-assay per cent CV = 1.7-8.7; intra-assay per cent CV = 2-4) and high recovery during sample clean-up make this method useful for the quantitation of verapamil in therapeutic monitoring and pharmacokinetic studies. 4. The method is illustrated with the pharmacokinetic results obtained for 14 healthy male volunteers who received a single 240 mg dose of the commercially available tablets of Dilacoron Retard 240 mg. The mean values for the area under the curve from 0 to 24 h (AUC[0-24]), maximum achieved concentration (Cmax) and time to achieve the maximum concentration (Tmax) were 863 ng h-1 ml-1, 112 ng/ml and 4 h, respectively

Comparación y sinergia en el tratamiento de la hipertensión arterial esencial / Synergy of verapamil and enalapril in the treatment of arterial hypertension

Se estudiaron 40 pacientes con hipertensión arterial esencial leve o moderada. Se administraron diariamente 240 mg verapamil o 10 mg de enalapril, así como placebo. El tiempo total del estudio fue de 24 semanas: 2 de "lavado" 6 con uno de los medicamentos, nuevo "lavado" de 2 semanas y 6 con el medicamento alterno. en quienes persistió la tensión artesial diastólica (TDA) superior a 90 mmHg, se administraron simultáneamente ambos medicamentos durante 8 semanas más. Los pacientes se asignaron de manera alterna a cada uno de los 2 grupos formados. Cuando el primer medicamento fue el verapamil, la TAD fue menor de 90 mmHg en 15 de 19 y con enalapril lo fue en 12 de 20. Con enalapril, como segundo medicamento, la TAD se normalizó en 16 de 19 y con verapamil en los 18 estudiados. Tres normalizaron su TAD con la administración simultánea de ambos. Dos pacientes abandonaron el estudio por razones personales y uno por la presencia de tos al usar el enalapril. No hubo ningún otro efecto colateral indeseable. Los estudios de laboratorio no mostraron cambios. La eficacia de ambos productos fue similar. La sinegia quedó evidenciada por la mejoría de los pacientes que no respondieron a un solo producto y sí lo hicieron al administrarlos juntos

Design for rectal administration of verapamil hydrochloride

Verapamil hydrochloride, formulated in rectal suppository dosage from different suppository bases, were used. The permeation of the drug through standard cellophane membrane and its dissolution in aqueous medium from the different formulations were performed at 37C. The water soluble base, polyethylene glycol showed the highest release of the drug. The drug release characteristics indicated adherence to first order kinetics mechanism. In vivo rabbit studies of two suppository formulations compared with intravenous and oral doses were performed. The rectal administration of verapamil hydrochloride in suppositories resulted in a more rapid onset and more intense depressor responses than the oral route

Further investigations of the central effects of a calcum-entry blocker [Verapamil]

The intracerebroventricular injection [ICVI] of the selective alpha2- agonist clonidine into anesthetized rabbits produced significant lowering in mean arterial blood pressure [B.P]. However, each of the entry selective - anatagonist yohimbine and the Ca2+ entry blocking agent verapamil produced transient increase in B.P. Pretreatment with yohimbine completely prevented the occurrence of the hypotensive effect of the subsequent dose of clonidine. Similarly, prior administration of verapamil, significantly attenuated clonidine-hypotensive effect. Both yohimbine and verapamil displayed considerable prophylactic activity against ouabain-induced arrhythmias in conscious mice. These results support the suggestion that alpha2- adrenoceptors play a role in the cardiovascular responses of Ca2+ - entry blockers. Verapamil injected intracerebroventricularly but not yothimbine, displayed protective capacity against neurological changes, including the convulsions, induced by central injection of ouabain into conscious mice. These results reflect the wide spectrum of the CNS actions of Ca2+ - entry blocker verapamil compared to those of alpha2- antagonists

Efectos del verapamil sobre los lípidos séricos / Effects of verapamil on serum lipids

Este trabajo fue realizado con el objetivo de estudiar el posible efecto hipolipemiante del verapamil. Se emplearon 35 conejos y se formaron 5 grupos experimentales; C = control (9 conejos) C + V = control + verapamil en dosis de 1,71 mg/kg/día, oral (6 conejos) HC = hipercolesterolémico (8 conejos); Vb-hipercolesterolémico + verapamil a baja dosis, l,71 mg/kg/d, oral (6 conejos); Va-hipercolesterolémico + verapamil a dosis alta 5,14 mg/kg/d, oral (6 conejos). Se observó una disminución de las concentraciones séricas de colesterol y fosfolípidos en el grupo Vb cuando se comparó con el grupo HC no tratado y en el grupo hipercolesterolémico que fue tratado con la dosis alta de verapamil se produjo un mayor incremento de estas variables cuando se comparó con el grupo HC. Concluyendo que la dosis baja de verapamil resultó más efectiva en disminuir estos lípidos del suero. No hubo diferencias significativas en las concentraciones de colesterol y fosfolípidos determinados en hígados y aorta de todos los grupos