PubMed Health⌕ Search

Biomedical subjects

A K Dash

Publications and source records attributed to A K Dash.

At least 19 recordsLinked to original sources
PubMed2005

Mycobacterium avium intracellularae complex associated extrapulmonary axillary lymphadenitis in a HIV-seropositive infant--a rare case report.

Opportunistic infections by Mycobacterium avium intracellulare complex in HIV infected patients, though common in adults, are rarely seen in infants. We herewith report an interesting case of an eight month old infant presenting with isolated axillary lymphadenitis, later on diagnosed to be tubercular lymphadenitis by Mycobacterium avium intracellulare and finally proved to be seropositive for HIV infection born to previously undetected HIV seropositive parents.

Antibiotics, Antitubercular↗
PubMed2002

X-ray powder diffractometric method for quantitation of crystalline drug in microparticulate systems. I. Microspheres.

Ethylcellulose microspheres containing tolnaftate (I) were prepared by the emulsion-solvent evaporation technique. An X-ray powder diffractometric method was developed to quantify the content of crystalline I in these microspheres. X-ray lines of I with d-spacings of 5.5 and 4.2 A were chosen for the quantitative analyses. Physical mixtures containing various weight fractions of I and blank (empty) microspheres were prepared and lithium fluoride (20% w/w) was added as the internal standard. The 5.5 and 4.3 A lines of I and the 2.3 A line of lithium fluoride were used for the quantitative analysis. A plot of the intensity ratio (intensity of the 5.5 A line of I/intensity of 2.3 A line of lithium fluoride) as a function of the weight percent of I in the mixture, resulted in a straight line. The crystalline content of I in the tolnaftate-loaded microspheres was determined using this standard curve. A second independent determination of the content of I was possible from the intensities of the 4.3 A line. The enthalpy of fusion of I, determined by differential scanning calorimetry (DSC), was also used as a measure of the crystalline content of I in the microspheres. The X-ray and DSC methods measure the content of crystalline I in the microspheres at room temperature ( approximately 25 degrees C) and at the melting point of I (111 degrees C), respectively. The total content of I in the microspheres was determined by HPLC. The DSC and X-ray results indicated that a substantial fraction of the incorporated I was dissolved in the ethylcellulose matrix.

Cellulose↗
PubMed2001

Evaluation of an acetic acid ester of monoglyceride as a suppository base with unique properties.

The objective of this investigation was to evaluate an acetic acid ester of monoglycerides made from edible, fully hydrogenated palm oil (AC-70) as a suppository base and compare it with a commercially available semisynthetic base (Suppocire AI). Benzocaine and miconazole were used as model drugs. Suppositories were prepared by the fusion method. The drug loads in the suppositories were kept at 2% to 5% (wt/wt). In vitro release of drug from the suppositories into Sorensen's phosphate buffer (pH 7.4) was studied using a US Pharmacopeia dissolution apparatus 1 and a spectrophotometer. The melting behavior of the bases and the physical state of the drug in the suppositories were studied using a differential scanning calorimeter (DSC). Powder x-ray diffractometry was used to study any possible polymorphic changes in the AC-70 base during formulation and storage. In vitro release studies revealed that the release of benzocaine from the AC-70 suppository was substantially slower than that of the commercial AI base. At a 2.5% (wt/wt) benzocaine load, the release of drug from the AC-70 suppositories was found to be linear. This slow and linear release was attributed to the physical property of the base, which forms liquid crystalline phases in the aqueous dissolution medium. The lyotropic liquid crystalline phase has the ability to incorporate drug into its structure and can control the release kinetics of the drug from such a system. The apparent pH of the release medium (water) was decreased by 1 to 1.5 pH units when the AC-70 base was used. The DSC studies revealed that the melting range of the AC-70 base is 36 degrees C to 38 degrees C, which is ideal for suppository formulations. The results of these studies support the possibility of using this new base for slow-release suppository formulations. This base may be of particular interest for a drug that requires an acidic environment to maintain its activity.

Acetates↗
PubMed2001

Effect of cross-linking on the in vitro release kinetics of doxorubicin from gelatin implants.

Doxorubicin is one of the most potent anti-tumor agents used generally in the treatment of bone cancer. Like other cancer chemotharepeutics, it produces undesirable side effects such as cardiotoxicity, which is especially severe when administrated via the conventional intravenous route. In order to minimize the systemic toxicities and to make this drug more suitable for the treatment of bone cancer, an implantable delivery system with cross-linked gelatin as the biodegradable matrix material was developed. This delivery system could possibly improve targeting of the drug as well as sustain the rate of release of the drug to the tumor. Glutaraldehyde was used as a cross-linking agent. Incorporation of glutaraldehyde in the matrix was needed to maintain the mechanical strength of the implant and to sustain the rate of release of the drug from the implant. Besides cross-linking the gelatin matrix, glutaraldehyde was found to cross-link the free amino group of doxorubicin. The effect of cross-linker concentration on the stability of the drug in the implant and on the rate and extent of release were also evaluated. In conclusion, cross-linked gelatin implants were developed for the local delivery of doxorubicin.

Antibiotics, Antineoplastic↗
PubMed2001

Evaluation of creatine transport using Caco-2 monolayers as an in vitro model for intestinal absorption.

Creatine is a nutraceutical that has gained popularity in both well-trained and casual athletes for its performance-enhancing or ergogenic properties. The major disadvantages of creatine monohydrate formulations are poor solubility and oral bioavailability. In the present study, creatine transport was examined using Caco-2 monolayers as an in vitro model for intestinal absorption. Confluent monolayers of Caco-2 cells (passage 25-35) were used for the permeability studies. Monolayers were placed in side-by-side diffusion chambers. (14)C-Creatine (0.1-0.5 microCi/mL) was added to either the apical or basolateral side, and the transport of the creatine across the Caco-2 monolayer was measured over a 90-min period. The apical to basolateral transport of (14)C-creatine was small, ranging from 0.2-3% of the original amount appearing on the receiver side in a 90-min period. Interestingly, the basolateral to apical permeability of radiolabeled creatine was substantially greater than that observed in the apical to basolateral direction. Studies with drug efflux transport inhibitors indicate that neither the P-glycoprotein nor multidrug resistance-associated protein is involved in the enhanced basolateral to apical transport of creatine.

Biological Transport, Active↗
PubMed2001

Cerebrospinal fluid penetration and pharmacokinetics of levofloxacin in an experimental rabbit meningitis model.

This study was designed to investigate the penetration across the blood-brain barrier of three doses of levofloxacin using a microdialysis probe implanted into the cerebrospinal fluid (CSF) of a rabbit pneumococcal meningitis model. The microdialysis guide cannula was implanted into rabbit subarachnoid space using a stereotaxic frame. After 3 days, 10(4) cfu Streptococcus pneumoniae serotype 3 in 0.3 mL saline was injected via intracisternal puncture and animals were allowed to incubate the organisms for 16-18 h. Groups of animals (n = 5) then received 7, 10.5 or 14 mg/kg iv of the drug over 10 min. Plasma samples were obtained via an ear vein 0, 0.25, 0.5, 0.75, 1, 2, 4, 6 and 8 h after the antibiotic infusion. CSF microdialysis effluent samples were collected every 0.5 h for the entire experiment. Plasma and microdialysis effluent samples were analysed by HPLC. AUC(0-8) in plasma and CSF were computed using the trapezoid rule. The elimination half-life in plasma and CSF was calculated using non-linear regression analysis. The unbound peak plasma concentrations for the three doses studied were 3.9, 6.4 and 10.3 mg/L, respectively. There was a significant increase in the plasma AUC(0-8) [29.7 +/- 6.3, 49.1 +/- 19.1 and 67.6 +/- 8.9 mg x h/L (P < 0.005)]. The unbound peak CSF concentrations were 3.8, 5.7 and 8.6 mg/L and occurred at 0-0.5 h after the administration of the dose. The AUC(CSF(0-8)) was significantly higher as the dose was increased (7 mg/kg, 15.8 +/- 6.6; 10.5 mg/kg, 37.3 +/- 7.8; and 14 mg/kg, 46.4 +/- 20.9 mg x h/L; P < 0.03). The penetration of levofloxacin averaged 53% for the 7 mg/kg dosage group, 76% for the 10.5 mg/kg group and 68% for the 14 mg/kg group. Our results demonstrate that levofloxacin penetration into the CSF averages 66% for the doses that would be used in clinical practice.

Animals↗
PubMed2000

Evaluation of quick disintegrating calcium carbonate tablets.

The purpose of this investigation was to develop a rapidly disintegrating calcium carbonate (CC) tablet by direct compression and compare it with commercially available calcium tablets. CC tablets were formulated on a Carver press using 3 different forms of CC direct compressed granules (Cal-Carb 4450, Cal-Carb 4457, and Cal-Carb 4462). The breaking strength was measured using a Stokes-Monsanto hardness tester. The disintegration and dissolution properties of the tablets were studied using USP methodology. The calcium concentration was determined by an atomic absorption spectrophotometer. Scanning electron microscopy was used to evaluate the surface topography of the granules and tablets. Breaking strength of Cal-Carb 4450, Cal-Carb 4457, and Cal-Carb 4462 tablets was in the range of 7.2 to 7.7 kg, as compared with a hardness of 6.2 kg and 10 kg for the commercially available calcium tablets Citracal and Tums, respectively. The disintegration time for the tablets presented in the order earlier was 4.1, 2.1, 1.9, 2.9, and 9.7 minutes, respectively. The dissolution studies showed that all formulations released 100% of the elemental calcium in simulated gastric fluid in less than 20 minutes. In summary, this study clearly demonstrated that quick disintegrating CC tablets can be formulated without expensive effervescence technology.

Calcium Carbonate↗
PubMed1999

Development of a rectal nicotine delivery system for the treatment of ulcerative colitis.

The aims of this investigation were: i. to develop a rectal nicotine delivery system with bioadhesives for the treatment of ulcerative colitis and ii. to evaluate nicotine transport and cytotoxicity of the delivery system using Caco-2 cell culture systems. Rectal nicotine suppository formulations were prepared in semi-synthetic glyceride bases (Suppocire AM and AI, Gattefosse Inc.) by fusion method. The in vitro release of nicotine was carried out in modified USP dissolution apparatus 1. Differential scanning calorimetry (DSC) and powder X-ray diffraction were used to study the polymorphic changes if any in the formulations. An LC method was used for the assay of nicotine. The effect of bioadhesives (glyceryl monooleate (GMO), and Carbopol) on the nicotine flux was evaluated using Caco-2 cell permeability studies and Caco-2 cell viability was determined using the MTT toxicity assay. In vitro release studies indicated that the low melting AI base was superior to that of the AM base. Presence of GMO in the formulation enhanced the release of nicotine whereas Carbopol showed an opposite effect. The enhanced release of nicotine in the presence of GMO was found to be partly due to the melting point lowering effect of this compound. Caco-2 cell absorption studies showed that there was a decrease in the flux of nicotine in the presence of both the bioadhesives. The flux of the fluorescein marker which is used to study the integrity of the cell monolayers was found to be slightly higher only in the presence of 10% (w/w) Carbopol. Nicotine, Carbopol, and GMO do not have any cytotoxic effect on these cell monolayers within the concentration range used in the formulations. Rectal nicotine formulations containing bioadhesives were developed and characterized. Both in vitro release and cell culture studies have indicated that one can manipulate the nicotine release from these rectal delivery systems by incorporation of various bioadhesives or the use of different bases in the formulation. Nicotine concentration below 2% (w/v) and bioadhesive concentration below 10% (w/w) do not have any cytotoxic effect on Caco-2 cells.

Acrylic Resins↗
PubMed1999

Simple liquid chromatographic method for the analysis of the blood brain barrier permeability characteristics of ceftriaxone in an experimental rabbit meningitis model.

A simple LC method was developed and validated for the analysis of ceftriaxone in aqueous and biological samples. Chromatographic separation was achieved on a reversed-phase C18 microbore column (Hypersil 5 microm, 200x2.1 mm) with UV detection at 270 nm. This isocratic system was operated at ambient temperature and required less than 10 min of chromatographic time. The flow-rate was maintained at 0.5 ml min(-1). Cetyltrimethylammonium bromide (0.01 M) was utilized as the ion-pairing agent. For the analysis of the drug in the aqueous system, the mobile phase consisted of methanol-acetonitrile-phosphate buffer, pH 7.4 (20:20:60, v/v/v). The plasma and CSF systems used the same mobile phase constituents in a slightly different ratio (30:40:30, v/v/v). Lidocaine was used as an internal standard and the peak height ratios of the drug to that of the internal standard were linear over the concentration range of 0.0 to 16 microg ml(-1) only in the case of aqueous systems. Within-day and day-to-day relative standard deviations ranged from 0.3 to 2.2% and 1.1 to 5.9%, respectively. This method was used to: (1) quantify ceftriaxone in an aqueous system, in rabbit plasma using a simple protein precipitation procedure, and in the CSF; (2) evaluate the permeability characteristics of ceftriaxone across the blood-brain barrier through quantification of ceftriaxone in the CSF using a microdialysis sampling technique; and (3) analyze the effects of dexamethasone (a synthetic fluorinated corticosteroid used for the relief of cerebral edema) on the permeability of ceftriaxone across the blood brain barrier through quantification of ceftriaxone in the dexamethasone-treated animals with meningitis.

Animals↗
PubMed1999

A simple HPLC method using a microbore column for the analysis of doxorubicin.

Doxorubicin is one of the most potent anti-tumor agents generally used in the treatment of bone cancer. A simple and sensitive HPLC method was developed and validated for the assay of doxorubicin. The method used a C18 Luna microbore column (50 x 1 mm) with a fluorescent detector (505 nm Ex. and 550 nm Em.). The mobile phase consisted of water-acetonitrile-acetic acid (80:19:1, v/v/v, pH 3.0) and the flow rate was 0.1 ml min(-1). Daunomycin was used as the internal standard. This isocratic system required a 10-min run-time, giving a detection limit of 0.02 ng (0.035 pmol per injection). Standard curves were linear over the concentration range of 0.01-0.1 microg ml(-1). Relative standard deviations (R.S.D.) for the within-day, day-to-day precision, and the accuracy measurement for the assay were less than 4.0, 3.2, and 4.1%, respectively. This HPLC method was used to study the in vitro release characteristics of doxorubicin from implantable drug delivery system.

Acetic Acid↗
PubMed1999

Development of an in vitro dissolution method using microdialysis sampling technique for implantable drug delivery systems.

The major challenge faced during the development of implantable dosage forms for site-specific delivery is monitoring the local concentration of the drug at or around the site of action. The tissue concentration at the site is generally measured by either sacrificing the animal at different points in time or by determining the amount of drug left in the implants at various time intervals. Unfortunately, there are no official in vitro dissolution methods available to study the release characteristics of drugs from this drug delivery system. The objective of this investigation was to develop a simple method using microdialysis sampling technique to serve as an in vitro dissolution method for implantable drug delivery systems. Ciprofloxacin implants were prepared by compressing ciprofloxacin microcapsules in poly(lactic acid) (PLA) and poly(lactic-glycolic acid) (PLGA). A sensitive HPLC method was developed and validated for the assay of Ciprofloxacin. An in vitro dissolution method was developed to study the release characteristics of drug from these implants. The method used a microdialysis sampling technique and a small sample volume of release medium. The various advantages and disadvantages of this method over other USP methods are discussed.

Anti-Infective Agents↗
PubMed1999

Use of gelatin-acacia coacervate containing benzocaine in topical formulations.

The in vitro release of a drug from topical formulations depends on the concentration of the drug in the formulation, the solubility of the drug in the base, the diffusion coefficient of the drug in the vehicle, and the partition coefficient of the drug between the vehicle, and the release medium. Incorporation of both complexing agents and cosolvents into such formulations has been used to enhance the in vitro release of a drug from topical formulations. In this investigation, a novel approach to enhance the in vitro release of benzocaine from different ointment formulations has been introduced. In this study, benzocaine was microencapsulated using gelatin-acacia complex coacervation technique. Various weight fractions of the coacervate, 5, 10, and 20% (w/w), were incorporated into both oleaginous and absorption bases. The in vitro release characteristics of benzocaine from the resulting ointments were studied using a modified USP Dissolution Apparatus 2. A plot of the cumulative amount of drug released (7-8%) per unit surface area versus (time)(1/2) was linear. Microscopic studies of the formulations revealed that the coacervates maintained their integrity in the formulation during the preparation and storage of the dosage form. Differential scanning calorimetric (DSC) studies indicated that the drug existed in the crystalline state in all formulations including those at a low drug load (0.5% w/w). DSC was also used to determine the solubility of the drug in the formulation. The rate and extent of drug release was higher in the absorption base as compared to the oleaginous base.

Administration, Topical↗
PubMed1998

Therapeutic applications of implantable drug delivery systems.

In the past, drugs were frequently administered orally, as liquids or in powder forms. To avoid problems incurred through the utilization of the oral route of drug administration, new dosage forms containing the drug(s) were introduced. As time progressed, there was a need for delivery systems that could maintain a steady release of drug to the specific site of action. Therefore, drug delivery systems were developed to optimize the therapeutic properties of drug products and render them more safe, effective, and reliable. Implantable drug delivery systems (IDDS) are an example of such systems available for therapeutic use. The application of currently available implantable drug delivery systems is the main focus of this review. IDDS can be classified into three major categories: biodegradable or nonbiodegradable implants, implantable pump systems, and the newest atypical class of implants. Biodegradable and nonbiodegradable implants are available as monolithic systems or reservoir systems. The release kinetics of drugs from such systems depend on both the solubility and diffusion coefficient of the drug in the polymer, the drug load, as well as the in vivo degradation rate of the polymer, especially, in the case of the biodegradable systems. Controlled release of drug from the implantable pump is generally achieved utilizing the microtechnology of electronic systems and remote-controlled flow rate manipulation through the maintenance of a constant pressure difference. The third atypical class includes those which have been recently developed such as ceramic hydroxyapatite antibiotic systems used in the treatment of bone infections, intraocular implants for the treatment of glaucoma, and transurethral implants utilized in the treatment of impotence. The major advantages of these systems include targeted local delivery of drugs at a constant rate, less drug required to treat the disease state, minimization of possible side effects, and enhanced efficacy of treatment. Also, these forms of delivery systems are capable of protecting drugs which are unstable in vivo and that would normally require a frequent dosing intervals. Due to the development of such sustained release formulations, it is now possible to administer unstable drugs once a week to once a year that in the past required frequent daily dosing. Preliminary studies using these systems have shown superior effectiveness over conventional methods of treatment. However, one limitation of these newly developed drug delivery systems is the fact that their cost-to-benefit ratio (cost/benefit) is too high which restricts their use over conventional dosage forms. Hopefully, in the future, new implantable systems can be developed at a lower cost, thereby minimizing the cost-to-benefit ratio and therefore, be used extensively in standard therapeutic practice. Some of the most recently discovered implants are in the early developmental stages and more rigorous clinical testing is required prior to their use in standard practice.

Animals↗
PubMed1996

Solid-state characterization of AG337 (Thymitaq), a novel antitumor drug.

AG337 (Thymitaq) is an antitumor compound synthesized by Agouron Pharmaceuticals, Inc., using protein structure-based drug design. AG337 is a hydrochloride salt with a molecular formula of C14H12N4OS.2HCl. This compound was subjected to thermal analyses, Karl Fischer titrimetry, powder X-ray diffractometry, scanning electron microscopy, and FTIR. On the basis of the Karl Fischer and thermogravimetric analysis, it was conclude to be a dihydrate. The differential scanning calorimetric studies revealed, that on heating, AG337 dehydrates and form a metastable form with a melting point of 213 degrees C followed by crystallization into a stable form at 261 degrees C. This stable form was finally melted at 312 degrees C with decomposition. On the basis of the FTIR and HPLC studies, it was concluded that the final exothermic peak at 320 degrees C was due to sample decomposition. The powder X-ray diffraction studies confirmed the existence of these two polymorphs of AG337. Scanning electron microscopic studies revealed that the crystal habits of both the polymorphs were quite different. FTIR spectra of both the polymorphs showed pronounced difference in the range of 600-1800 cm-1.

Antimetabolites, Antineoplastic↗
PubMed1993

A liquid chromatographic method for the determination of tolnaftate in pharmaceutical formulations.

A simple LC method was developed and validated for the analysis of tolnaftate in various pharmaceutical formulations. This method did not require any complex sample extraction procedure. The chromatographic separation was achieved on a reversed-phase, C18 column with UV detection at 258 nm. This isocratic system was operated at ambient temperature and required 9 min of chromatographic time. The mobile phase consisted of methanol-aqueous potassium dihydrogen phosphate solution (80:20, v/v) at a flow rate of 1.5 ml min-1. Standard curves were linear over the concentration range of 1.0-51.0 micrograms ml-1. Within-day and between-day relative standard deviation values ranged from 0.7 to 2.9% and from 1.3 to 3.4%, respectively. This method was used to quantify tolnaftate in microcapsule, microsphere, cream, powder, liquid, liquid aerosol and powder aerosol formulations. This method was also used to study the stability of tolnaftate in solution during its extraction from microcapsule formulations.

Aerosols↗
PubMed1992

An implantable dosage form for the treatment of bone infections.

The object of this investigation was the development of an implantable sustained-release dosage form, for the treatment of bone infections. Cross-linked polydimethylsiloxane (PDMS) was used as the matrix material. The drug delivery system was prepared by incorporating tobramycin, as a free base (C18H37N5O9.H2O) or as a sulfate salt [(C18H37N5O9)2.5H2SO4], into the matrix and molding into spherical beads. Following in vitro studies, the cumulative amount of drug released when plotted as a function of the square root of time was linear for both the base and the salt. The addition of glycerol to the matrix substantially accelerated the rate of drug release and the plots of cumulative amount of drug released continued to be linear as a function of the square root of time. The glycerol-incorporated beads swelled in contact with the aqueous medium but a negligible amount of glycerol was released even after exposure to the medium for 20 days. 13C solid-state and high-resolution NMR studies indicated that a fraction of the added glycerol participated in the cross-linking reaction of the polymer. The effect of the initial molecular weight of PDMS and the effect of the concentration of the cross-linker on the kinetics of drug release were investigated.

Cross-Linking Reagents↗
PubMed1991

A liquid-chromatographic method for the determination of tobramycin.

A rapid and sensitive liquid-chromatographic method was developed to quantify the release of tobramycin from polymeric drug delivery systems in vitro. Pre-column derivatization of tobramycin and kanamycin B sulphate (internal standard) was carried out with 2,4,6-trinitrobenzenesulphonic acid. The sample volume required was only 50 microliters. The chromatographic separation was achieved on an octyl reversed-phase column with UV detection at 340 nm. This isocratic method was performed at ambient temperature and required only 8 min of chromatography time. The standard curves were linear over the concentration range 0.50-50.0 mg l-1. Inter-day and intra-day relative standard deviations ranged from 3.6 to 9.3% and from 1.6 to 6.8%, respectively. The assay method was used to determine the tobramycin content in different pharmaceutical formulations and to study the stability of the drug both in the solid-state and in solution.

Buffers↗