PubMed · 5513545
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H L Smith, R D Neff. 1970. Linear absorption coefficients for gamma-rays in tissue.. https://pubmed.ncbi.nlm.nih.gov/5513545/
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Parent beta-cyclodextrin (beta-CyD) and 2-hydroxypropyl-beta-CyD (HP-beta-CyD) form 1:1 solid complexes with an orally active angiotensin-converting enzyme inhibitor, captopril, while hydrophobic perbutanoyl-beta-CyD (TB-beta-CyD) forms a solid dispersion or solid solution with the drug. The binary system of captopril/HP-beta-CyD or captopril/TB-beta-CyD and the ternary system of captopril/TB-beta-CyD/HP-beta-CyD in different molar ratios were prepared by the kneading method, and the release behavior of the drug was investigated. The release rate of captopril from the binary HP-beta-CyD system was rather fast, whereas that from the binary TB-beta-CyD system was comparatively slower, the retarding effect being dependent on the amounts of TB-beta-CyD. The release rate from the ternary captopril/TB-beta-CyD/HP-beta-CyD system was slowed down by the addition of small amounts of HP-beta-CyD, whereas the rate became faster as the molar ratio of HP-beta-CyD further increased (>.25 molar ratio). Both water penetration studies and microscopic observation suggested that the retarding effect is attributable to a gel formation of HP-beta-CyD in the TB-beta-CyD hydrophobic matrix. It was difficult to prolong plasma levels of captopril by administering orally either the binary HP-beta-CyD or TB-beta-CyD system in dogs. On the other hand, the ternary captopril/TB-beta-CyD/HP-beta-CyD system (molar ratio of 1:0.5:0.5) gave a plasma profile comparable to that of a commercially available sustained release preparation (Captoril R). Therefore, a combination of HP-beta-CyD and TB-beta-CyD is useful for the controlled release of water-soluble drugs such as captopril.
The decomposition of p-hydroxybenzoic acid, an important pollutant present in the wastewaters of the olive oil industry, has been carried out by a direct photolysis provided by a polychromatic UV radiation source, and by ozone. In both processes, the conversions obtained as a function of the operating variables (temperature, pH and ozone partial pressure in the ozonation process) are reported. In order to evaluate the radiation flow rate absorbed by the solutions in the photochemical process, the Line Source Spherical Emission Model is used. The application of this model to the experimental results provides the determination of the reaction quantum yields which values ranged between 8.62 and 81.43 l/einstein. In the ozonation process, the film theory allows to establish that the absorption process takes place in the fast and pseudo-first-order regime and the reaction is overall second-order, first-order with respect to both reactants, ozone and p-hydroxybenzoic acid. The rate constants are evaluated and vary between 0.18x10(5) and 29.9x10(5) l/mol s depending on the temperature and pH.
A total of three free amine chitosans (CS J, CS L and CS H) and two soluble chitosan salts (CS G and CS HCl) were evaluated for their efficacy and safety as nasal absorption enhancers of peptides based on in situ nasal perfusion and subacute histological evaluation in rat. At 0.5% w/v, all chitosans were effective in enhancing the nasal absorption of [D-Arg(2)]-Kyotorphin, an enzymatically stable opioid dipeptide. The enhancing effect of the free amine chitosans increased as the pH was decreased from 6.0 to 4.0 (P<0.05). However, the pH effect was not significant for the two chitosan salts (P0.05), suggesting that their adjuvant activity may be less pH-dependent than the free amine form. CS J and CS G were subsequently selected for further studies. At only 0.02% w/v, their enhancing effect was already significant and comparable to that of 5% w/v hydroxypropyl-beta-cyclodextrin (HP-beta-CD). Both chitosans at 0.1% caused minimal release of total protein and phosphorus from the rat nasal mucosa, with the values similar to that of 5% HP-beta-CD. At 0. 5% the two chitosans also stimulated smaller release of lactate dehydrogenase, an intracellular enzyme used as marker of nasal membrane damage, than 1.25% dimethyl-beta-cyclodextrin. Morphological evaluation of the rat nasal mucosa following 2-week daily administration indicated that the two chitosans (1.0%) produced only mild to moderate irritation. In conclusion, both the free amine and the acid salt forms of chitosans are effective in enhancing the nasal absorption of [D-Arg(2)]-Kyotorphin and have potential for further studies as a safe and effective nasal absorption enhancer of peptide drugs.