Drug design and delivery最新文献

The use of Eudragit L100, a copolymer based on methacrylic acid and methacrylic acid methyl ester, in preparing erythromycin microspheres is described. The microspheres were simply prepared in liquid paraffin by solidifying an Eudragit L100 in ethanol solution. When gelatin was incorporated in the solidifying solution, the resultant microspheres were more spherical and had a smooth surface. The size of the microspheres could be controlled by varying the Eudragit L100 concentration in ethanol, and erythromycin was incorporated with 60-70% efficiency. The degradation of erythromycin by acid was markedly protected when the erythromycin microspheres were coated with the polymer. The in vitro release rate of erythromycin from the microspheres was also modified by the coating process. The feasibility of preparing formulations of erythromycin for oral administration, which release the drug at a controlled rate, and protect the drug from gastric acid, is thus demonstrated.

In vitro and further in vivo work with a conjugate formed from the cytotoxic drug 1-beta-arabinofuranosylcytosine (ara-C) and dextran 2000 are described. In the preparation of this conjugate, functionalisation of ara-C was via N4-(4-carboxybutyryl)-ara-C (glu-ara-C), permitting conjugation with amino groups introduced by prior reaction of the oxidised dextran with ethylenediamine; by varying the proportions of the reaction components, 5.4 to 7.7% w/w loadings of ara-C were obtained. At physiological pH, in vitro, drug release from a 5.4% loaded conjugate was gradual and was dominantly ara-C; at lysosomal pH (pH 5) the release rate was much slower and more ara-U was formed. Antitumour effects were evaluated in L1210 leukaemic mice following single (1 day after inoculation) or double (2 and 6 days after inoculation) intraperitoneal injection of ara-C, glu-ara-C, or a 7.7% loaded conjugate at three dose levels. In all cases, the increase in lifespan was greatest following use of the conjugate, but the differences in the effects of ara-C and the conjugate were only significant at the lowest dose level. Glu-ara-C was virtually inactive under all conditions.

Nonleast-squares jackknife regression was applied to model a quantitative structure-activity relationship (QSAR) analysis of butyrophenones. Dependent physicochemical and dependent psychopharmacological parameters were correlated, and the robustness of the model was confirmed by resampling.

In this review, the complex physical and chemical interactions of drugs with model and biological membranes under normal and pathological conditions are examined at the molecular level. The results of our own published and unpublished structural studies are discussed and correlated with kinetic binding studies to assess the potential role of nonspecific drug interaction with the membrane bilayer in the overall receptor binding mechanism for membrane-bound receptors in heart and brain.

The mode and mechanism of action of Sefsol-318, a medium chain glyceride and a potent percutaneous absorption enhancer, on the in vitro permeation of papaverine hydrochloride through hairless rat skin were investigated and compared with those of laurocapram (Azone). The total amount of the drug delivered through excised skin over 28 h from aqueous solutions of the drug in which 5% S-318 or Azone was suspended was about 820 or 420 times higher, respectively, than from the solution alone. Experiments using liposomes as models, indicated that both the enhancers markedly increased the fluidity of lipid membranes. Skin conductance measurements in hairless rats indicated that they both also increased in vivo skin moisturizing and water holding capacity. These results suggest that the mechanism of action of Sefsol-318 and Azone in enhancing skin permeation are similar. But following in vitro pretreatment of the excised skin with 5% Sefsol-318 and aqueous emulsion for 2 h, skin permeation of papaverine hydrochloride through the pretreated skin was much lower than through non-treated skin in the presence of Sefsol-318. In contrast, the enhancing effect of Azone on the pretreated skin was similar to that of Azone on the in vitro non-treated skin. We found that, unlike Azone, Sefsol-318 disappeared from skin completely one day after 24 h-in vivo pretreatment of skin with aqueous gels containing each agent. In agreement, drug permeation through skin excised one day after the in vivo pretreatment with Sefsol-318 was almost the same as in non-pretreated controls without Sefsol-318. This difference in the mode of action of Sefsol-318 and Azone may arise from the difference in the residence times of these enhancers in skin.

The (H+/K+)-ATPase enzyme inhibitory activity of omeprazole analogues (Figure 1) and 1-aryl-4-methyl-2,3-dihydropyrrolo[3,2-c]quinolines (Figure 2) was found to be significantly correlated with electronic (sigma) or pKa parameter that governs the basicity of the molecules. The former compounds are representative of irreversible blockers, and the latter of reversible blockers. Inclusion of hydrophobic (pi) and/or steric (Es) parameters sometimes led to improvement in the correlations, suggesting that these parameters may play a role in the formation of a cyclic intermediate. The derived significant correlation equations strongly support a mechanism of action, first proposed by Lindberg et al., involving such a cyclic intermediate.

New thermo-responsive hydrogels were synthesized by copolymerizing acryloyl-L-proline methyl ester (A-ProOMe) with minor amounts of 2-hydroxypropyl methacrylate (HPMA) or polyethylene glycol 600 dimethacrylate (14G), using gamma-rays from a 60Co source. In water, extensive swelling of the hydrogels occurred at 10 degrees C, but there was marked deswelling as the temperature was raised to 37 degrees C. The poly(A-ProOMe-co-HPMA) hydrogel was characterized by an initial rapid shrinkage at the surface in the deswollen state; this shrinkage arose because of the formation of a rigid membrane barrier devoid of micropores. The system is therefore 'surface regulated'. In contrast, no such a barrier formed in the deswollen poly(A-ProOMe-co-14G) hydrogel. The whole matrix shrunk without the disappearance of micropores, and it is therefore a 'matrix pumping' system. Testosterone was incorporated into both these types of hydrogels, and the drug-loaded hydrogels were implanted subcutaneously into the backs of castrated rats. The daily dose of testosterone released in vivo from the poly(A-ProOMe-co-HPMA) hydrogel was constant at approximately 30 micrograms/day throughout an experimental period of 54 weeks. In contrast, drug release from the poly(A-ProOME-co-14G) hydrogel reached a maximum after one week and then decreased linearly with time down to the 7th week, when it was undetectable. These conclusions were supported by the changes in weight of the ventral prostates and right-side seminal vesicles of the rats, which were restored to normal when delivery of the testosterone was sustained.

Thirteen previously described 5-(p-substituted-phenyl)-2'-deoxyuridines were synthesized, and the NMR and IR spectra of their 2,4-dioxopyrimidine (2,4-DP) rings were correlated against linear free energy-related and extrathermodynamic parameters. We conclude that the 5-phenyl ring is probably oriented over the plane of the 2,4-DP ring (sandwich structure, Figure 6). The main component of the spectroscopic data is largely determined by the stereoelectronic nature of the para-groups in the 5-phenyl ring, while a second component is largely determined by apolar forces. The inhibitory activity of the compounds against thymidylate synthetase is enhanced by the presence of apolar groups with a positive inductive effect, provided these groups do not extend the plane of the 2,4-DP ring.