PubMed · 7037907
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1982. Teeth beautiful.. https://pubmed.ncbi.nlm.nih.gov/7037907/
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Hydrogels of carbomer (C) loaded with model slightly soluble fluoroquinolone antimicrobials (AMFQ), norfloxacin (I) and ciprofloxacin (II) were prepared to evaluate their physical and delivery properties. Thus, dispersions of 0.25% of C loaded with 0.2-0.5 mol equivalents of AMFQ and 0.2-0.5 mol equivalents of NaOH yielded pseudoplastic hydrogels with a high negative electrokinetic potential and good physical stability. Concentration of AMFQ in the hydrogels was, respectively, 7.2 and 34 times higher than I and II aqueous solubility, indicating a high increase in aqueous compatibility. Release of AMFQ in bicompartimetal Franz type cell occurred by zero order kinetics. Delivery rate constant (k(0)) was five to six times higher as water was replaced by NaCl solution as receptor medium. Release in agar dishes revealed that, even under high dilution, delivery remains modulated. Intestinal absorption flux coefficient in everted rat intestine (k(U)) were measured with reference solutions (RS) of free AMFQ (k(U)(RS) II>k(U)(RS) I) and with hydrogels (H), in which the pattern was reversed since k(U)(H) I>k(U)(H) II. As expected k(U)(H) II was 0.55 times lower than k(U)(RS) II. However, k(U)(H) I was 1.37 times higher than its reference, which cannot be explained from the analysis of k(0) and k(U)(RS) alone. Hydrogels C-AMFQ behave as a reservoir of AMFQ able to deliver it at a constant rate and would be useful to design topical and or systemic dosage forms.
Eudragit RS and RL are biocompatible non-swelling polymers that widely used in the preparation of sustained release drug delivery systems. In this study, the effect of thermal treating on the tensile strength of tablets and release of indomethacin from Eudragit RS and RL matrices were investigated. The results showed that thermal treating at 40 degrees C has no effect on the release of the drug, whereas heat-treating at temperatures higher than 50 or 60 degrees C decreases the release rate of indomethacin from Eudragit RS or RL, respectively. It was shown that the duration of the heat treatment was also an important factor in controlling the release rate of indomethacin from Eudragit matrices. The results showed that an increase in the duration of the heat treatment from 2 to 24 h resulted in a reduction in the release rate of the drug. The heating of the matrices over 24 h had no significant effect on the release rate of indomethacin. It was shown that heat treatment of the matrices over the glass transition temperature of the polymer can prolong the drug release but had no significant effect on the tensile strength of tablets.
This review article summarizes recent results on the development of macromolecular carriers for thermal targeting of therapeutics to solid tumors. This approach employs thermally responsive polymers in conjunction with targeted heating of the tumor. The two thermally responsive polymers that are discussed in this article, poly(N-isopropylacrylamide-co-acrylamide) (poly(NIPAAm)) and an artificial elastin-like polypeptide (ELP), were designed to exhibit a soluble-insoluble lower critical solution transition in response to increased temperature slightly above 37 degrees C. In vivo fluorescent videomicroscopy and radiolabel distribution studies of ELP delivery to human tumors implanted in nude mice demonstrated that hyperthermic targeting of the thermally responsive ELP for 1 h provides a approximately two-fold increase in tumor localization compared to the same polypeptide without hyperthermia. Similar results were also obtained for poly(NIPAAm) though the extent of accumulation was somewhat lesser than observed for the ELP. The endocytotic uptake of a thermally responsive ELP was also observed to be significantly enhanced by the thermally triggered phase transition of the polypeptide in cell culture for three different tumor cell lines. Preliminary cytotoxicity studies of an ELP-doxorubicin conjugate indicate that the ELP-doxorubicin conjugate has near equivalent cytotoxicity as free doxorubicin in a cell culture assay.