Biomedical subjects

H Zia

Publications and source records attributed to H Zia.

27 records · Page 2Linked to original sources

PubMedDate not supplied

Preparation of controlled release anticancer agents. I: 5-Fluorouracil-ethyl cellulose microspheres.

Microspheres of 5-fluorouracil have been prepared, using three grades of ethyl cellulose as wall forming materials, and utilizing a solvent evaporation technique under ambient conditions. An alcoholic solution of 5-fluorouracil and polymer was dispersed in liquid paraffin containing 33.3 per cent n-heptane. The effect of stirring rate, time of stirring, drug loading, and polymer grade on drug release in two different media were evaluated. The drug loaded particles were spherical in shape and had a diameter range of 25-200 mm and were suitable for incorporating into a gel base. Drug release studies in aqueous media, showed that acidic media provide a faster release rate than neutral media. The drug release study from an aqueous gel base preparation at pH 7.0 through a synthetic membrane was found to be promising for formulation of a gel-microsphere product for the treatment of skin lesions.

Administration, Topical↗

PubMedDate not supplied

Biopharmaceutical evaluation of a tablet dosage form made from ethyl cellulose encapsulated aspirin particles.

Ethyl cellulose encapsulated aspirin particles, suitable for preparation of direct compression tablets were prepared by the solvent evaporation method. Ethyl acetate was used as a solvent for the polymer in combination with a saturated solution of aspirin as the dispersing medium to prevent partitioning and drug loss. This resulted in a high yield of free-flowing, non-aggregated particles. In vitro-in vivo evaluations of the experimental aspirin tablets (made by direct compression of ethyl cellulose encapsulated particles) and three different commercial aspirin products (a conventional tablet, a timed-release tablet, and a timed-release caplet) were undertaken. Comparison of the dissolution in acidic media at pH 1.2 showed different release profiles for these products. While the conventional tablet and the timed-release caplet showed the highest and the lowest rate of release, respectively; the timed-release tablet and the experimentally made tablet revealed an intermediate rate and very similar release profiles. The cumulative urinary excretion data collected in a complete crossover study, using five healthy subjects further indicated that the experimental tablet has an in vivo availability identical to that of the timed-release tablet.

Adult↗

PubMedDate not supplied

Coating charcoal with polyacrylate-polymethacrylate copolymer for haemoperfusion. I: Fabrication and evaluation.

A potential haemoperfusion system has been developed using activated charcoal encapsulated with a polyacrylate-polymethacrylate copolymer. The film forms a coating of great mechanical strength around the charcoal particles, which is readily permeable to water and certain dissolved substances. The charcoal granules were coated with various membrane thicknesses consisting of a 2-10 per cent (by weight) film coat, using the modified method of non-solvent addition of Benita et al. (1985). The effect of various encapsulation variables such as stirring rate, rate of addition of non-solvent, percentage of coating polymer and concentration of a non-wall-forming polymer (PIB) in the non-solvent phase on adsorptivity, as well as the release of fine particles, were determined. The effect of coating thickness on the adsorption rate of the coated charcoal was investigated by constructing Higuchi diffusion model plots using methylene blue as a model adsorbate. It was found that the membrane permeability can be adjusted by changing experimental conditions to obtain high adsorption capacity along with a low level of released particles. Further, the effect of presoaking of the coated charcoal in purified water, normal saline, and 0.067 M phosphate buffer pH 7.4 (for 24 h at 37 degrees C) on the rate of adsorption of methylene blue was also evaluated.

Acrylic Resins↗

PubMedDate not supplied

Coating charcoal with polyacrylate-polymethacrylate copolymer for haemoperfusion. II. Drug removal and polymer compatibility studies.

The newly developed system of polyacrylate-polymethacrylate-coated charcoal, filled in a column has been tested for its efficiency in removing theophylline, as a model drug both from a buffer solution pH 7.4 and human plasma using a closed-circuit apparatus. Preliminary testing determined the capacity of the charcoal column and the effect of circulation rate of the buffer solution on the clearance of theophylline. It was found that the circulation rate does not significantly affect the clearance rate of theophylline, while the concentration of drug in the buffer solution has a considerable effect on the clearance of the drug, presumably due to the saturation of the column. The clearance of the drug from plasma in comparison to buffer solution was also investigated. It was found that more than 70 per cent of the drug was removed from the buffer solution within the first 15 min as compared with 65 per cent from plasma; with 95 per cent removed from buffer after 1 h in comparison to 93 per cent from plasma. The blood compatibility of the polymer was studied by incubating various concentrations (5-25 per cent w/v) of the polymer in blood for 30 min at 25 degrees C. A concentration of 5 per cent polymer was also incubated for a series of incubation times. The results indicated that with polymer concentrations up to 15 per cent there is no significant lysis of RBCs in comparison to a blank.(ABSTRACT TRUNCATED AT 250 WORDS)

Acrylic Resins↗

PubMedDate not supplied

Coating charcoal with polyacrylate-polymethacrylate copolymer for haemoperfusion. III: The effect of the coat thickness on the adsorptioncapacity of the coated charcoal and its adsorptivity to small and middle size molecules.

In this study, the effect of the coat thickness of polyacrylate-polymethacrylate copolymer on the adsorption capacity of activated charcoal to methylene blue as a model marker was investigated by constructing both Langmuir and Freundlich isotherms. It was found that the coat thickness significantly affected the adsorption coefficient of the coated charcoal to methylene blue as is reflected by the attractive forces between the adsorbent and the adsorbate. This effect is understandable as the membrane will act as a barrier between the adsorbent and the adsorbate. The coat thickness also had some effect on the adsorption capacity of activated charcoal but not as much as it affected the adsorption coefficient. The data followed the Freundlich isotherm more closely than the Langmuir equation. The effect of the coat thickness on the adsorption of selected drugs of different molecular size was also investigated using theophylline, paracetamol, sodium phenobarbital, creatinine and vitamin B12 as model drugs. The results showed that the adsorption patterns of theophylline, paracetamol and sodium phenobarbital were more or less similar. The apparent coating thickness did not affect the extent of adsorption of these model drugs and there was little effect on the adsorption rate especially during the first 15 min. The adsorption of vitamin B12 and creatinine showed completely different patterns which are discussed in detail.

Acrylic Resins↗

PubMedDate not supplied

Release kinetics of liposome-encapsulated ganciclovir after intravitreal injection in rabbits.

This study was undertaken to establish experimentally whether the intravitreal application of liposomally-entrapped ganciclovir could prolong intraocular therapeutic levels when it is compared to the intravitreal injection of a simple solution of the drug. New Zealand white rabbits were given an intravitreal injection of the drug solution and of liposome-encapsulated ganciclovir. The intravitreal clearance of ganciclovir was determined after a single injection of either the drug solution (200 micrograms/0.1 mL) or the liposomally-entrapped (with 41% load; 82 micrograms drug load and 118 micrograms free) ganciclovir. The ganciclovir vitreal concentrations were measured at various time intervals for a period up to 43 days using an HPLC method. The results of this study clearly demonstrated that prolonged intravitreal drug levels (above the mean inhibitory dose of cytomegalovirus of 1 microgram/mL) after administration of the liposome-entrapped ganciclovir and estimated to continue beyond 30-43 days. The injection of the 200 micrograms/0.1 mL of drug solution showed a mean vitreous concentration which was higher than the ID50 only for 55 h. The disappearance rate constant for the liposome-encapsulated injections was approximately 22 x slower than simple drug solution injections (controls). No evidence of retinal toxicity was found by clinical or light microscopy examination of the treated eyes.

Animals↗

PubMedDate not supplied

Effect of cyclosporine A formulations on bovine corneal absorption: ex-vivo study.

The purpose of this study was to evaluate, in an ex-vivo study, the absorption of cyclosporine A on bovine cornea after 24 h contact with various drug delivery systems containing 1% cyclosporine A and in comparison with an olive oil formulation as the reference vehicle for cyclosporine A. The different formulations studied were poly(acrylic acid) polymeric gels in aqueous/non-aqueous solvents, polyisobutylcyanoacrylate nanocapsules, and a combination of both formulations. The histological effects of these formulation on corneal cells after 24 h of contact were also studied. The lowest absorption rate of cyclosporine A was found using olive oil with a percent absorption of 2.52 +/- 1.52% (259 +/- 171 micrograms/g cornea). The three formulations developed for this study, nanocapsules, poly(acrylic acid) polymeric gel and nanocapsules gel showed significantly better absorption of CsA than olive oil, with a mean percent absorption of 5.81 +/- 2.04% (621 +/- 218 micrograms/g cornea), 6.09 +/- 2.93% (651 +/- 313 micrograms cornea) and 7.92 +/- 2.55% (847 +/- 273 micrograms/g cornea) respectively. As we studied the penetration of cyclosporine A into the different layers of the cornea, we observed that for all formulations, CsA remained at the corneal surface and did not penetrate the whole cornea. The histological study showed that olive oil, nanocapsules and poly(acrylic acid) gel in aqueous/non-aqueous solvents show some modifications on the cornea, contrary to the nonocapsules gel which did not indicate any toxic effect. The nanocapsule gel, with the highest percent absorption along with its margin of safety on the cornea, seems to present a new promising drug delivery system for ocular administration.

Acrylic Resins↗

PubMedDate not supplied

Emulsion formulations of testosterone for nasal administration.

The nasal route has received a great deal of attention due to the many advantages of nasal delivery over parenteral administration. The male sex hormone testosterone is ineffective when administered orally due to its gut wall and first-pass metabolism. Therefore, an alternative method for delivery would be the intranasal route, if the lack of aqueous solubility can be overcome. In this study a new approach to emulsion formulations of the drug has been proposed based on the hypothesis that increased absorption is possible upon solubilization of the drug and/or prolongation of the formulation residence time in the nose. Three differently charged testosterone submicron size emulsion formulations with various zeta potentials (+24.8, -23.0 and 0.06 mV) were prepared as nasal spray formulations. A dose of approximately 3.8 mg testosterone per rabbit was administered to four rabbits and the bioavailability of the emulsion formulations was assessed and compared with an i.v. formulation via solid-phase extraction, followed by an HPLC analysis method. Statistical analysis of the normalized data indicated a bioavailability of 55, 51 and 37% for positively, negatively and neutrally charged emulsions respectively. The results of this study strongly suggest that emulsion formulations have some potential to be considered for nasal delivery. Further, both the positively and negatively charged emulsion formulations provided a better bioavailability than the neutral charged emulsion, probably indicating that the charged particle interactions between emulsion globules and the mucus layer prolong the contact of drug with nasal membrane thus enhancing drug absorption.

Absorption↗

PubMedDate not supplied

Indomethacin reduces lung adenoma number in A/J mice.

The effects of indomethacin on A/J mice were investigated. The non-steroidal antiinflammatory drug (NSAID) indomethacin reduced significantly the number of lung adenomas 3, 4 or 8 months after urethane injection by 28, 30 and 29% respectively. The density of apoptotic cell bodies increased 2.9-fold in the lung adenomas of A/J mice treated with indomethacin. By immunocytochemistry, COX-2 immunoreactivity was present in the cytosol of lung adenomas, and in epithelial cells lining the bronchioli and bronchus as well as type 2 alveolar cells. COX-1 immunostaining was similar to that of COX-2 in the lungs of urethane-injected mice treated with or without indomethacin. By RT-PCR, COX-1 and COX-2 PCR products were present in mouse lung adenomas, alveoli and bronchioli. These results suggest that indomethacin may inhibit COX-1 and COX-2 in the A/J mouse lung resulting in reduced adenoma formation.

Adenoma↗