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Biomedical subjects

M R Gasco

Publications and source records attributed to M R Gasco.

At least 37 records · Page 2Linked to original sources
PubMed1997

Effect of oil phase composition on the skin permeation of felodipine from o/w microemulsions.

Oil/water microemulsions containing benzyl alcohol or different ratios of benzyl alcohol and isopropyl myristate as oil phase were prepared and used as vehicles for the transdermal absorption of felodipine. Skin permeation from the microemulsions was compared with that from a drug suspension in an apparent external phase of a microemulsion and with an aqueous drug suspension. The highest flux was from the microemulsion with the highest solubility of felodipine, while the permeation rate decreased over time from the suspension in the apparent external phase. The flux from the aqueous suspension was 10-50 times lower than that from the microemulsions. These results indicate that microemulsions containing benzyl alcohol may be interesting vehicles for transdermal administration of felodipine.

Administration, Cutaneous↗
PubMed1996

Influence of counter ions on the skin permeation of methotrexate from water--oil microemulsions.

The influence on the permeation of methotrexate across intact hairless mouse skin of different counter ions added to water--oil (w/o) microemulsions containing lecithin, as surfactant, and water--propylene glycol at different pH values, as internal phase, was studied. As counter ions, monooctyl phosphate, monodecyl phosphate, monodecyl glycerophosphate, taurodeoxycholate, dodecyl sulfate and dioctyl sulfosuccinate were used. At pH 4.0, the transport of methotrexate was enhanced by the counter ions and a marked increase in the flux of the drug was measured when dodecyl sulfate and dioctyl sulfosuccinate were used. At pH 5.0 only a slight increase of the flux was observed. The increased permeation was attributed to the lipophilization of methotrexate as a consequence of ion pair formation.

Animals↗
PubMed1995

Pseudo-ternary phase diagrams of lecithin-based microemulsions: influence of monoalkylphosphates.

The formation of macroscopically homogeneous, stable, fluid, optically transparent, isotropic solutions (microemulsions) was delineated, at 25 degrees C, for systems containing water, soybean lecithin, sodium monoalkylphosphate (hexyl or ocytl), alcohol and isopropyl myristate. Six straight or branched alcohols (1-butanol, 2-butanol, isobutanol, 1-pentanol, 2-pentanol, 3-pentanol) were investigated as co-surfactants. A constant lecithin/alcohol mixing ratio was used, while the aqueous phase consisted of a solution of alkylphosphates at different concentrations. An increase of the microemulsion domain was seen by increasing the concentration of the alkylphosphate. With 0.2m hexylphosphate, as aqueous phase, the microemulsion domain consisted of a single, region, that, in the presence of butylic alcohols, spanded the greater portion of the phase diagram. In the presence of amyl alcohols the area of this region was much smaller. With 0.2 m octylphosphate the realm of existence of the microemulsions, except for 1-pentanol, consisted of two regions separated by a liquid-crystal region. With all the alcohols examined, the liquid-crystal phase solubilized a larger amount of oil in the presence of octylphosphate than in the presence of hexylphosphate. The stability ranges of microemulsions in systems containing soybean, lecithin, alcohol, water, and isopropyl myristate can be greatly increased by using a second hydrophobic amphiphile, such as hexylphosphate, to adjust the hydrophilic-lipophilic balance or the spontaneous peaking properties of lecithin-alcohol systems.

Chemistry, Pharmaceutical↗
PubMed1994

Inhibition of lipoperoxidation of linoleic acid by five antioxidants of different lipophilicity.

The efficacy of oxidation inhibition of five natural and synthetic antioxidants (BHT, BHA, nordihydroguaiaretic acid (NDGA), quercetin and rutin) was studied in O/W emulsions. Linoleic acid was used as a reference molecule; the reaction was initiated by an azo-compound. The kAH characterizing the reaction of the antioxidant with the peroxyl radical decreases in the following order: kAH(BHA) > kAH(BHT) > kAH(NDGA) > kAH(quercetin) > kAH(rutin).

Antioxidants↗
PubMed1993

Calorimetric study on the solubilization of butanol by alkylphosphate and alkylphosphate-lecithin systems.

Microcalorimetric studies on alkylphosphate-butanol and alkylphosphate-butanol-lecithin systems were carried out as a first step to study the role of butanol (used as cosurfactant) in the formation of microemulsions. The enthalpy of solubilization; delta H, of the same amount of butanol (1.806 mol kg-1) in aqueous sodium monoalkyl-phosphates, with a hydrocarbon chain varying from 6 to 10 carbon atoms, was investigated as a function of alkylphosphate concentration. Measurements were performed in the presence and in the absence of lecithin. The enthalpy values measured upon addition of butanol to the mixtures were negative in all cases. Below the critical micelle concentration (CMC) of the alkylphosphates, the heats of butanol dissolution were found to decrease upon increasing the concentration of the alkylphosphate. This behaviour was related to the dissolution of butanol in water and to the formation of mixed butanol-alkylphosphate and butanol-alkylphosphate-lecithin micelles. Above the CMC essentially constant delta H values were found. The delta H measured may be the sum of simultaneous effects--heat of alcohol dissolution and the simple alkylphosphate micelle dissociation or alkylphosphate-lecithin mixed aggregate dissociation and the heat of mixed micelle formation. The delta H at the plateaus were linearly related to the corresponding CMC values of the alkylphosphates.

Butanols↗
PubMed1992

Timolol in lipospheres.

Lipospheres carrying timolol (1) were obtained from microemulsions. They had lecithin, palmitic and decanoic acids as the main constituents. The sizes were between 300 and 400 nm and the amount of 1 incorporated varied from 2.7 to 4.8% according to the microemulsion used. Compound 1 was present in the lipospheres mainly as ion pairs in order to increase its lipophilicity. The difference found in the incorporation was principally due to the different lipophilicity of the ion pairs of 1.

Chemistry, Pharmaceutical↗
PubMed1991

Optimization of doxorubicine incorporation and of the yield of polybutylcyanacrylate nanoparticles.

The preparation from w/o microemulsion of polybutylcianacrylate nanocapsules incorporating doxorubicine was optimized applying a multivariate experimental design. Different variables were investigated; the responses were polymer yield, concentration of the drug in the particles and percentage of the drug incorporated. A preliminary study was carried out with the strategy of fractional factorial design; the following step was a central composite design in order to study the most important causal variables. The information collected were treated by the response surface method (REGFAC package). The optimization allowed to maximize the responses; an incorporation of about 10% of doxorubicine and a yield of about 95% were obtained, starting from values notably lower of both incorporation and yield.

Doxorubicin↗
PubMed1991

Doxorubicine englobed in polybutylcyanoacrylate nanocapsules: behaviour in vitro and in vivo.

Nanocapsules of polybutylcyanoacrylate containing doxorubicine were prepared from w/o microemulsion. A concentration of about 10% of the drug was obtained. After washing, dispersion and lyophilization of the nanocapsules, some experiments were performed in vivo and in vitro. About 1% of doxorubicine was released in vitro in 48 hours; after injection on the hairless back of rabbits, the nanoparticles without the drug gave any inflammatory processes, while the nanocapsules containing doxorubicine gave a deeper and more prolonged ulcer than that of the same amount of doxorubicine in solution, indicating that practically all the drug was inside the nanocapsules.

Animals↗
PubMed1989

Microemulsions as topical delivery vehicles: ocular administration of timolol.

The topical administration of timolol as an ion-pair with octanoate was achieved by use of an oil-in-water microemulsion containing lecithin as a surfactant. The microemulsion, a solution of the ion-pair and a solution of timolol alone were instilled in the conjunctival sac of rabbits. A rapid method for the separation and determination of timolol in aqueous humour by HPTLC was used. The bioavailability of timolol from the microemulsion and the ion-pair solution was higher than that obtained from timolol alone. The areas under the curve for timolol in aqueous humour after administration of the microemulsion and the ion-pair solution were 3.5 and 4.2 times higher, respectively, than that observed after the administration of timolol alone.

Absorption↗