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Biomedical subjects

A R Kulkarni

Publications and source records attributed to A R Kulkarni.

At least 19 recordsLinked to original sources
PubMed2006

Time and pH dependent colon specific, pulsatile delivery of theophylline for nocturnal asthma.

In this study, investigation of an oral colon specific, pulsatile device to achieve time and/or site specific release of theophylline, based on chronopharmaceutical consideration. The basic design consists of an insoluble hard gelatin capsule body, filled with eudragit microcapsules of theophylline and sealed with a hydrogel plug. The entire device was enteric coated, so that the variability in gastric emptying time can be overcome and a colon-specific release can be achieved. The theophylline microcapsules were prepared in four batches, with Eudragit L-100 and S-100 (1:2) by varying drug to polymer ratio and evaluated for the particle size, drug content and in vitro release profile and from the obtained results; one better formulation was selected for further fabrication of pulsatile capsule. Different hydrogel polymers were used as plugs, to maintain a suitable lag period and it was found that the drug release was controlled by the proportion of polymers used. In vitro release studies of pulsatile device revealed that, increasing the hydrophilic polymer content resulted in delayed release of theophylline from microcapsules. The gamma scintigraphic study pointed out the capability of the system to release drug in lower parts of GIT after a programmed lag time for nocturnal asthma. Programmable pulsatile, colon-specific release has been achieved from a capsule device over a 2-24h period, consistent with the demands of chronotherapeutic drug delivery.

Animals↗
PubMed2006

Phacoemulsification in true exfoliation of the lens capsule: a case series.

PURPOSE: We report five cases (seven eyes) of true exfoliation during an 18-month period. Of the two bilateral cases, the first was identified immediately before cataract surgery and the second spontaneously developed a split in the anterior capsule just before capsulorrhexis, mimicking a partial capsulorrhexis. In the three unilateral cases, true exfoliation was noted during the first examination. METHODS: Vision blue aided uneventful capsulorrhexis differentiating its edge from the true exfoliation edge, and in the first two cases, the anterior capsule was sent for histopathology and ultrasound of the fellow eye was requested. RESULTS: Ultrasound and histopathology demonstrated lamellar separation of the anterior portion of the lens capsule, confirming the diagnosis of true exfoliation. Cataract surgery by phacoemulsification was uneventful in all cases. CONCLUSION: True exfoliation of the lens capsule can masquerade as a partial capsulorrhexis and should be looked for before surgery and immediately before capsulorrhexis to avoid creating a partial thickness capsulorrhexis and its related surgical complications. No zonule weakness was appreciated in our cases. To our knowledge, the spontaneous occurrence of a curvilinear lamellar capsular dehiscence with a flap before capsulorrhexis has not been reported before. This series highlights that cataracts associated with true exfoliation of the lens capsule can be safely operated, with the help of vision blue, by routine phacoemulsification without having to convert to the extracapsular technique.

Aged↗
PubMed2005

Ocular manifestations of head injury: a clinical study.

AIM: This prospective study aimed to clinically correlate the various ocular findings with the neurological status in cases of closed head injury. METHODS: A total of 200 consecutive cases of closed head injury admitted to a major teaching hospital underwent a thorough ophthalmic assessment. The Glasgow coma scale (GCS) and the Revised trauma score (RTS) were applied to grade the severity of injury and assess the prognosis. Kendall's tau-b and Fisher's exact test were used in the analysis. RESULTS: The main causes of head injury were road traffic accidents 52.5% followed by assaults in 34%. Ocular involvement was found in 167(83.5%) cases. These included corneal and scleral tears in 2%, subconjunctival haemorrhage or ecchymosis in 46%, orbital fractures 12%, pupillary involvement 6.5%, papilloedema 5.5%, intraocular trauma 5.5%, proptosis 3%, lateral rectus palsy 2%, lacrimal gland prolapse 1%, and optic nerve trauma 0.5%. All 21 patients (10.5%) who died had eye involvement. In all, 150 cases (75%) with a RTS of 12 had a good prognosis. Of these 124 (82.6%) had ocular involvement of no neurological significance. CONCLUSIONS: Although sophisticated imaging techniques are available to localize lesions, early ophthalmic assessment in correlation with the GCS aids in prognosticating outcomes. Pupillary involvement, papilloedema, and ocular motor paresis pointed to a more severe head injury. To our knowledge, this is the only prospective study recording ocular findings in the first few hours and attempting a correlation with the final outcome.

Accidents, Traffic↗
PubMed2002

An assessment of solubility profiles of structurally similar hazardous pesticide in water + methanol mixture and co-solvent effect on partition coefficient.

This paper reports solubility and partition coefficient data for the structurally similar pesticides, fenvalerate and cypermethrin, measured by UV spectrophotometry in binary mixtures of methanol and water at different temperatures. The solubility of both pesticides is much higher in methanol than in water at all temperatures. Partition coefficients were also measured between water+heptanol immiscible mixtures at 298.15K, and these data show a decrease with increasing composition of methanol in water.

Insecticides↗
PubMed2001

Chemically modified polyacrylamide-g-guar gum-based crosslinked anionic microgels as pH-sensitive drug delivery systems: preparation and characterization.

New spherically shaped cross-linked hydrogels of polyacrylamide-grafted guar gum were prepared by the emulsification method. These were selectively derivatized by saponification of the -CONH2 group to the -COOH group. The derived microgels were characterized by FTIR and elemental analyses. The derivatized microgels were responsive to pH and ionic strength of the external medium. The swelling of microgels increased when the pH of the medium changed from acidic to alkaline. Transport parameters, viz., solvent front velocity and diffusion coefficients were calculated from a measurement of the dimensional response of the microgels under variable pH conditions. The variation in pH changed the transport mechanism from Case II (in 0.1 N HCl) to non-Fickian (in pH 7.4 buffer), and these processes are relaxation-controlled. Ionic strength exerted a profound influence on the swelling of the microgels. Swelling was reversible and pulsatile with the changing environmental conditions. The pH-sensitive microgels were loaded with diltiazem hydrochloride and nifedipine (both antihypertensive drugs) and their release studies were performed in both the simulated gastric and intestinal pH conditions. The release was relatively quicker in pH 7.4 buffer than observed in 0.1 N HCl; the release followed non-Fickian transport in almost all the cases.

Acrylic Resins↗
PubMed2001

Biodegradable polymeric nanoparticles as drug delivery devices.

This review presents the most outstanding contributions in the field of biodegradable polymeric nanoparticles used as drug delivery systems. Methods of preparation, drug loading and drug release are covered. The most important findings on surface modification methods as well as surface characterization are covered from 1990 through mid-2000.

Adsorption↗
PubMed2001

In-vitro release kinetics of cefadroxil-loaded sodium alginate interpenetrating network beads.

This paper reports the development of new interpenetrating polymeric networks of sodium alginate with gelatin or egg albumin cross-linked with a common cross-linking agent, glutaraldehyde, for the in-vitro release of cefadroxil. The beads formed were characterized by Fourier transform infra-red spectroscopy, scanning electron microscopy and differential scanning calorimetry. Swelling/drying experiments were performed to compute the diffusion coefficients and the molecular mass between cross-links of the beads. The release results were evaluated using an empirical equation to understand the transport mechanism. The extent of cross-linking was studied in terms of the size and release characteristics of the beads. The experimental and derived quantities have been used to study their dependencies on the nature of the polymeric beads, transport mechanism, encapsulation efficiency and drug diffusion, as well as the cross-linking abilities of the polymers.

Albumins↗
PubMed2001

Development of hollow microspheres as floating controlled-release systems for cardiovascular drugs: preparation and release characteristics.

Hollow microspheres of cellulose acetate loaded with four cardiovascular drugs (nifedipine [NFD], nicardapine hydrochloride [NCD], verapamil hydrochloride [VRP], and dipyridamole [DIP]) were prepared by a novel solvent diffusion-evaporation method. The oil-in-water emulsion prepared in an aqueous solution of 0.05% poly(vinyl alcohol) medium with ethyl acetate, a water-soluble and less toxic solvent, was used as the dispersing solvent. The yield of the microspheres was up to 80%. The microspheres had smooth surfaces, with free-flowing and good-packing properties. Scanning electron microscopy (SEM) confirmed their hollow structures, with sizes in the range 489-350 microm. The microspheres tended to float over the gastric media for more than 12 h. The drug loaded in hollow microspheres was in an amorphous state, as confirmed by differential scanning microscopy (DSC). The release of the drugs was controlled for more than 8 h. The release kinetics followed different transport mechanisms depending on the nature of the drug molecules.

Algorithms↗
PubMed2001

In vitro release study of verapamil hydrochloride through sodium alginate interpenetrating monolithic membranes.

Polymeric sodium alginate interpenetrating network membranes containing verapamil hydrochloride were fabricated for transdermal application. The membranes were evaluated for their physical properties, weight and thickness uniformity, water vapor transmission, as well as drug content uniformity. All the thin patches were transparent, smooth, and flexible. The drug-loaded membranes were analyzed by X-ray diffraction to understand the drug polymorphism inside the membrane. The transdermal patches were permeable to water vapor, indicating the permeability characteristics of the polymers. The in vitro drug release was performed in distilled water using a Keshary-Chien diffusion cell. The release data were analyzed to understand the mechanism of drug release.

Alginates↗
PubMed2001

Microspheres as floating drug-delivery systems to increase gastric retention of drugs.

Gastric emptying is a complex process, which is highly variable and makes in vivo performance of the drug-delivery systems uncertain. In order to avoid this variability, efforts have been made to increase the retention time of the drug-delivery systems for more than 12 h. The floating or hydrodynamically controlled drug-delivery systems are useful in such applications. The present review addresses briefly the physiology of the gastric emptying process with respect to floating drug-delivery systems. In recent years, the multiparticulate drug-delivery systems are used in the oral delivery of drugs. One of the approaches toward this goal is to develop the floating microspheres so as to increase the gastric retention time. Such systems have more advantages over the single-unit dosage forms. The development of floating microspheres involves different solvent evaporation techniques to create the hollow inner core. The present review addresses the preparation and characterization of the floating microspheres for the peroral route of administration of the drug.

Administration, Oral↗
PubMed2000

Solubility study of hazardous pesticide (chlorpyrifos) by gas chromatography.

Solubility data of a hazardous pesticide like chlorpyrifos are important in order to determine its residual toxicity from soil and to understand its controlled release characteristics. In this paper, solubility of chlorpyrifos was measured by using gas chromatography in pure water, methanol, and water-methanol mixtures at 298.15, 303. 15, and 308.15K. The results indicate that chlorpyrifos is more soluble in methanol than in water. The solubility of chlorpyrifos in water can be enhanced by adding methanol to water. The effect of temperature on the solubility of chlorpyrifos was observed at higher methanol content in the mixture.

Chlorpyrifos↗
PubMed2000

Glutaraldehyde crosslinked sodium alginate beads containing liquid pesticide for soil application.

This paper presents experimental results on the successful encapsulation of a natural liquid pesticide 'neem (Azadirachta Indica A. Juss.) seed oil' hereafter designated as NSO, using sodium alginate (Na-Alg) as a controlled release (CR) polymer after crosslinking with glutaraldehyde (GA). The NSO-containing beads have been prepared by changing the experimental variables such as the extent of crosslinking and the amount of loading in order to optimize the process variables. The absence of chemical interactions between active ingredients and polymer as well as crosslinking agent was confirmed by FTIR spectral measurements. The SEM data indicated that the structure of the walls of the beads are smooth and nonporous. The swelling results indicated that swelling of the polymeric beads decreases with increasing exposure time to the crosslinking agent. However, no significant variation in swelling was observed with different amounts of NSO loading. In order to understand the crosslinkability and its effect on the NSO release patterns of the beads, an attempt was made to calculate the molar mass between crosslinks using the Flory-Rehner equation. The release data have been fitted to an empirical equation to estimate the kinetic parameters.

Alginates↗
PubMed2000

Preparation of cross-linked sodium alginate microparticles using glutaraldehyde in methanol.

Polymeric sodium alginate microparticles were prepared by precipitating sodium alginate in methanol, followed by cross-linking with glutaraldehyde. The extent of cross-linking was controlled by the time of exposure to glutaraldehyde. The topology of microparticles was characterized by scanning electron microscopy (SEM), which indicated smooth surfaces. The equilibrium swelling experiments were carried out in water to observe the effect of cross-linking and drug loading for better utility of microparticles. It was found that swelling decreased, but drug loading increased, with an increase in cross-linking of the matrix.

Alginates↗
PubMed2000

Controlled release of antihypertensive drug from the interpenetrating network poly(vinyl alcohol)-guar gum hydrogel microspheres.

Poly(vinyl alcohol)-guar gum interpenetrating network microspheres were prepared by cross-linking with glutaraldehyde. Nifedipine, an antihypertensive drug, was loaded into these matrices before and after cross-linking to study its release patterns. The extent of cross-linking was analyzed by Fourier transform infrared spectroscopy and differential scanning calorimetry. Furthermore, the microspheres were characterized for drug entrapment efficiency, particle size, transport of water into the matrix and drug release kinetics. Scanning electron microscopic photographs confirmed the spherical nature and surface morphology. The mean particle size of the microspheres was found to be around 300 microm. The molecular transport phenomenon, as studied by the dynamic swelling experiments, indicated that an increase in cross-linking affected the transport mechanism from Fickian to non-Fickian. The in vitro release study indicated that the release from these microspheres is not only dependent upon the extent of cross-linking, but also on the amount of the drug loaded as well as the method of drug loading.

Antihypertensive Agents↗
PubMedDate not supplied

Encapsulation of antihypertensive drugs in cellulose-based matrix microspheres: characterization and release kinetics of microspheres and tableted microspheres.

This study is an attempt to prepare microspheres loaded with two antihypertensive drugs viz., nifedipine (NFD) and verapamil hydrochloride (VRP) using cellulose-based polymers viz., ethyl cellulose (EC) and cellulose acetate (CA). Emulsification and solvent evaporation methods were optimized using ethyl acetate as a dispersing solvent. The particles are spherical in shape and have smooth surfaces, as evidenced by the scanning electron microscopy. The microspheres were characterized for their particle size and distribution, tapped density and encapsulation efficiency. Smaller sized particles with a narrow size distribution were produced with EC when compared to CA matrices. Molecular level drug distribution in the microspheres was confirmed by differential scanning calorimetry. The microspheres were directly compressed into tablets using different excipients. The drug release from CA was faster than EC microspheres and, also, the VRP release was faster than NFD. The excipients used in tableting showed an effect on the release as well as the physical properties of the tablets.

Antihypertensive Agents↗
PubMedDate not supplied

Urea-formaldehyde nanocapsules for the controlled release of diclofenac sodium.

Urea-formaldehyde (UF), polymerized in situ in aqueous media, is a rigid polymer that can be used in the controlled release of bioactive molecules. During the process of polymerization, liquid neem seed oil (NSO) was encapsulated at three different loadings, which was then replaced by diclofenac sodium (DS), the presence of which was confirmed by FTIR spectra. The nanocapsules thus prepared were evaluated for percentage loading of the drug, particle size and release characteristics. Thermal analysis and x-ray data were obtained to understand the physical nature of the encapsulated drug. The surface characteristics of the nanocapsules were studied using a scanning electron microscope. Particles in the size range around 500 nm were obtained. The percentage loading efficiency of NSO was approximately 90-95, whereas for DS, the loading efficiency was only 50-60%. Complete release of the drug from the matrices occurred in 24 h, whereas, at 8 h only 60% of the drug was released.

Calorimetry, Differential Scanning↗
PubMedDate not supplied

Crosslinked chitosan microspheres for encapsulation of diclofenac sodium: effect of crosslinking agent.

Microspheres of chitosan crosslinked with three different crosslinking agents viz, glutaraldehyde, sulphuric acid and heat treatment have been prepared to encapsulate diclofenac sodium (DS). Chitosan microspheres are produced in a w/o emulsion followed by crosslinking in the water phase by one of the crosslinking methods. Encapsulation of DS has been carried out by soaking the already swollen crosslinked microspheres in a saturated solution of DS. Microspheres are further characterized by FTIR, x-RD and SEM. The in-vitro release studies are performed in 7.4 pH buffer solution. Microspheres produced are spherical and have smooth surfaces, with sizes ranging between 40-230 microm, as evidenced by SEM. The crosslinking of chitosan takes place at the free amino group in all the cases, as evidenced by FTIR. This leads to the formation of imine groups or ionic bonds. Polymer crystallinity increases after crosslinking, as determined by x-RD. The method adopted for drug loading into the microspheres is satisfactory, and up to 28-30% w/w loading is observed for the sulphuric acid-crosslinked microspheres, whereas 23-29 and 15-23% of loadings are obtained for the glutaraldehyde (GA)- and heat-crosslinked microspheres, respectively. Among all the systems studied, the 32% GA crosslinked microspheres have shown the sloxvest release i.e. 41% at 420 min, and a fastest release of 81% at 500 min is shown by heat crosslinking for 3 h. Drug release from the matrices deviates slightly from the Fickian process.

Chitin↗