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  • 1
    ISSN: 1573-904X
    Keywords: estradiol ; chemical delivery system ; brain enhanced drug delivery ; blood–brain barrier ; pharmacokinetics ; redox drug delivery
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The pharmacokinetics of a dihydropyridine–pyridinium salt-type chemical delivery system (CDS) for brain-targeted delivery of estradiol (E2) were examined in dogs. Parameters evaluated in vitro included stability in buffers and biological fluids and plasma protein binding. In vivo studies examined drug and metabolite concentrations in plasma, urine, and cerebrospinal fluid as well as in selected brain regions. The administered lipophilic E2-CDS disappeared very quickly from plasma and was not detected in urine. The oxidized drug form, E2-Q+, was excreted unchanged or as a conjugate in the urine for as long as 2 weeks. Plasma levels were below assay detection limits at later times. Pharmacokinetic analysis of urine E2-Q+ levels allowed estimation of a half-life of 2.2 days. Amounts of E2-Q+ excreted into the urine were proportional to the dose but averaged only 13.9% of the dose, indicating that other routes of excretion must be considered. CSF levels were below the limit of detection for both E2-CDS and E2-Q+, however, brain tissue concentrations of E2-Q+ were similar in several brain regions of individual animals examined 1 or 3 days after drug dosing.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Pharmaceutical research 9 (1992), S. 1275-1278 
    ISSN: 1573-904X
    Keywords: soft corticosteroid ; loteprednol etabonate ; metabolism ; tissue distribution ; transdermal permeability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The soft corticosteroid, loteprednol etabonate (chloromethyl 17α-ethoxycarbonyloxy-11β-hydroxy-3-oxoandrosta-1,4-diene-17β-carboxylate), I, was designed based on the “inactive metabolite approach.” Accordingly, I should be metabolized by hydrolysis to the corresponding inactive cortienic acid derivative, II. The in vitro and in vivo metabolism of I indeed yielded mainly this inactive metabolite, which is more hydrophilic and thus readily eliminated from the body. Relatively high levels of I were found in tissues after intravenous administration of the drug in rats. The permeability of I through hairless mouse skin was comparable to what has been found for related “hard” steroids, without significant metabolism taking place in the skin.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-904X
    Keywords: soft corticosteroid ; loteprednol etabonate ; pharmacokinetics ; metabolism ; excretion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. Pharmacokinetics, metabolism and excretion of loteprednol etabonate (LE) were investigated in rats. Methods. The pharmacokinetic studies were performed by iv injections of LE (1-20 mg/ kg). In the metabolism and excretion studies, 0.5-10 mg/kg of LE were iv administered, bile and urine samples were collected for 6 hr. Results. The pharmacokinetic of LE showed a rapid, dose-dependent elimination with a total blood clearance (CLtotal) of higher than 60 ml/min/kg. The metabolism and excretion of LE also showed a marked dose-dependency. At 6 hr after iv of LE (0.5-10 mg/kg), the total recoveries (LE and the metabolites, AE & A, in bile and urine) were 99.35-26.72%. However, only about 2% of LE was excreted from the body through the urine. There were 0.93-2.12% and 0.66-0.26% of AE, and 75.67-19.69% and 20.74-2.77% of A excreted in the bile and urine, respectively. The excretion of A was dose dependent, and significantly higher at the lower dose. Using the (% of total excretion) vs. (log dose) plots, it could be predicted that almost all of the administered LE will be metabolized, and excreted as A when the systemic dose is lower than 0.25 mg/kg. Conclusions. The results indicate that LE absorbed systemically, after topical administration, can be rapidly transformed to the inactive metabolites, and eliminated from the body mainly through the bile and urine.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1573-904X
    Keywords: soft corticosteroid ; loteprednol etabonate ; oral delivery ; rectal delivery ; inflammatory bowel disease
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. As a safe anti-inflammatory corticosteroid, the utility of loteprednol etabonate (LE) for the treatment of gastrointestinal inflammation, via oral and rectal administration, was investigated in rats. Methods. In vivo, LE solution and suspension were orally administered (20 mg/kg), and various LE preparations (solution, suspension & suppository) were applied in rectal loops (0.2 mg per loop). In vitro, various GI tissues were used to study the stability and partition of LE. Results. After oral administration of LE solution, LE reached the upper GI tract effectively, but not the colon, due to absorption and/or decomposition. In suspension, LE reached most of the GI tract (except rectum) in 8 hr and showed little absorption. After rectal applications, LE remained intact in the rectal loop for more than five hours with a slow rate of disappearance, however, LE distributed in the rectal membrane to some extent. The concentrations of LE and its inactive metabolites in plasma after both oral and rectal administrations were lower than the detection limit (0.1 µg/ml) at anytime during the experiments. In vitro, LE in solution was stable in stomach, but not in cecum, due to the hydrolysis by the cecal resident micro flora. In solution, LE distributed into the mucosal membranes efficiently (about 2.5 ~ 4.0 µg/g tissue). Conclusions. The results suggest that LE can be orally or rectally delivered in the GI tract for the topical treatment of the inflammatory bowel disease.
    Type of Medium: Electronic Resource
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