Fluconazole distribution in rat dermis following intravenous and topical application: a microdialysis study

The objective of this study was to investigate the skin distribution of fluconazole, a water-soluble antifungal agent, following intravenous (i.v.) and topical administration in the awake freely moving rat. Following i.v. bolus injection of fluconazole (10 mg/kg), a dual-site microdialysis sampling was performed in jugular vein and dermis in five rats. In addition, cutaneous absorption was studied by dermal microdialysis sampling following topical application of Diflucan Gel 0.5% to 12 rats. Fluconazole microdialysate concentrations were measured by on-line HPLC. To calibrate in vivo the probes, a fluorinated analog (UK-54737) of fluconazole was used as retrodialysis marker after demonstrating that recoveries were no different. Following i.v. bolus injection, fluconazole rapidly penetrates into the dermis. Cutaneous microdialysis sampling provided dermal concentrations of fluconazole, which were very similar to the unbound plasma concentrations determined by vascular microdialysis. The distribution equilibrium was rapidly achieved with a dermis-to-plasma partition coefficient of 1.02+/-0.04 (n=5). Following topical application of 0.5 g of Diflucan Gel containing 0.5% of fluconazole, active unbound concentrations in dermis were measured by cutaneous microdialysis for 11 h after application. The area under the curve (AUC) of fluconazole in dermal dialysate was relatively constant to an implantation depth of approximately 350 microm. Below this depth, the AUC progressively decreased with increasing implantation depth of the probe. Finally, this study shows that cutaneous microdialysis is an effective and minimally invasive tool to evaluate the dermal pharmacokinetics of fluconazole following intravenous or topical administration.     

Pharmacokinetics and dosage adjustment in patients with hepatic dysfunction

The liver plays a central role in the pharmacokinetics of the majority of drugs. Liver dysfunction may not only reduce the blood/plasma clearance of drugs eliminated by hepatic metabolism or biliary excretion, it can also affect plasma protein binding, which in turn could influence the processes of distribution and elimination. Portal-systemic shunting, which is common in advanced liver cirrhosis, may substantially decrease the presystemic elimination (i.e., first-pass effect) of high extraction drugs following their oral administration, thus leading to a significant increase in the extent of absorption. Chronic liver diseases are associated with variable and non-uniform reductions in drug-metabolizing activities. For example, the activity of the various CYP450 enzymes seems to be differentially affected in patients with cirrhosis. Glucuronidation is often considered to be affected to a lesser extent than CYP450-mediated reactions in mild to moderate cirrhosis but can also be substantially impaired in patients with advanced cirrhosis. Patients with advanced cirrhosis often have impaired renal function and dose adjustment may, therefore, also be necessary for drugs eliminated by renal exctretion. In addition, patients with liver cirrhosis are more sensitive to the central adverse effects of opioid analgesics and the renal adverse effects of NSAIDs. In contrast, a decreased therapeutic effect has been noted in cirrhotic patients with β-adrenoceptor antagonists and certain diuretics. Unfortunately, there is no simple endogenous marker to predict hepatic function with respect to the elimination capacity of specific drugs. Several quantitative liver tests that measure the elimination of marker substrates such as galactose, sorbitol, antipyrine, caffeine, erythromycin, and midazolam, have been developed and evaluated, but no single test has gained widespread clinical use to adjust dosage regimens for drugs in patients with hepatic dysfunction. The semi-quantitative Child-Pugh score is frequently used to assess the severity of liver function impairment, but only offers the clinician rough guidance for dosage adjustment because it lacks the sensitivity to quantitate the specific ability of the liver to metabolize individual drugs. The recommendations of the Food and Drug Administration (FDA) and the European Medicines Evaluation Agency (EMEA) to study the effect of liver disease on the pharmacokinetics of drugs under development is clearly aimed at generating, if possible, specific dosage recommendations for patients with hepatic dysfunction. However, the limitations of the Child-Pugh score are acknowledged, and further research is needed to develop more sensitive liver function tests to guide drug dosage adjustment in patients with hepatic dysfunction.     

The effect of tooth size discrepancy on occlusion: An experimental study.

The purposes of this experimental study are the following: (1) to compare the anterior and overall tooth size ratios reported by Bolton to values reported in epidemiologic studies, (2) to assess the accuracy of tooth size discrepancy measurements, (3) to investigate to what extent generalized tooth size discrepancy affects occlusion, (4) to investigate the effect of leveling the curve of Spee, and (5) to evaluate the effect of extraction therapy of 4 premolars on occlusion. For the first part of the study, Bolton's mean anterior and overall tooth size ratio (as well as the extraction values) were compared with calculations derived from 4 publications reporting mean mesiodistal tooth width by using the t test (P 相似文献   

The effects of substance P on the biomechanic properties of ruptured rat Achilles' tendon

OBJECTIVE: To determine whether injection of substance P into the paratendinous region of a ruptured and subsequently sutured rat Achilles' tendon alters the biomechanic properties of the tendon. DESIGN: Interventional animal study. SETTING: Animal laboratory at a university hospital. ANIMALS: Ninety-six 2-month-old, male Sprague-Dawley rats. INTERVENTION: Injection of saline, substance P (10(-6)micromol/kg of body weight [BW] or 10(-8)micromol/kg BW) associated with neutral endopeptidase inhibitors, or neutral endopeptidase inhibitors alone into the paratendinous region of ruptured and subsequently sutured rat Achilles' tendons from the second until the sixth day postoperatively. MAIN OUTCOME MEASURES: Stress at maximal load and work to maximal load and stiffness. RESULTS: Stress at maximal load was higher in the groups injected with substance P than in the saline group in the first, second, and sixth weeks. Work to maximal load was higher from the second until the sixth weeks in the substance P-treated groups than in the saline group. Stiffness did not differ between the 4 groups in any of the weeks. CONCLUSIONS: Injection of substance P into the paratendinous region of ruptured and subsequently sutured rat Achilles' tendons improved tendon healing by enhancing stress at maximal load and work to maximal load. However, stiffness was not significantly affected.     

Carbonated apatites obtained by the hydrolysis of monetite: Influence of carbonate content on adhesion and proliferation of MC3T3-E1 osteoblastic cells

The influence of the carbonate content in apatites on the adhesion and the proliferation of MC3T3-E1 osteoblastic cells was investigated. B-type carbonated apatites (DCAps) were prepared by the hydrolysis of monetite (CaHPO₄, DCP) in solutions with a carbonate concentration ranging from 0.001 to 0.075 mol l^?1. Stoichiometric hydroxyapatite (DCAp0) was synthesized in carbonate-free solution. MC3T3-E1 cells were seeded on the compacted DCAps and cell adhesion and proliferation were analysed after 24 h and 7 days, respectively, using a MTS assay and fluorescence microscopy. Cell adhesion tends to increase with increasing carbonate content for carbonate contents between 0 and 6.9 wt.% and levels out to an acceptable value (±50% compared to the control) for carbonate contents between 6.9 and 16.1 wt.%. Only DCAps with a carbonate content equal to or higher than 11% support high cell proliferation comparable to the control. On the latter DCAps, the cells have a spread morphology and form a near-confluent layer. A decrease in charge density and crystallinity at the apatite surface, as well as the formation of more spheroidal crystals with increasing carbonate content, might attribute to changes in composition and three-dimensional structure of the protein adsorption layer and hence to the observed cell behaviour. Consequently, only DCAps with a high carbonate content, mimicking early in vivo mineralization, are possible candidates for bone regeneration.     

The tibialis tendon as a valuable anterior cruciate ligament allograft substitute: biomechanical properties

The study evaluates the biomechanical properties of single-strand and single-loop tibialis (anterior and posterior) tendon allografts. A comparison was made with bone-patellar tendon-bone (BPTB) allografts. Sixty-four tendon allografts were evaluated in this study. Sixteen of these were single-strand tibialis anterior (TA) and 16 single-strand tibialis posterior (TP) tendons. Sixteen single-loop TA and TP tendons were also tested. The fourth group was composed of 16 BPTB allografts. The biomechanical properties determined were maximal load, stiffness, cross-sectional area and elongation. The results of this study showed that the maximal load of the single-loop tibialis tendons (1,553 ± 62 N) was greater than of the BPTB (1,139 ± 99 N), TA (776 ± 43 N) and TP (888 ± 64 N) tendons. The stiffness of the single-loop tibialis tendons (236 ± 10 N/mm) was also greater than of the BPTB (168 ± 13 N/mm), TA (60 ± 2 N/mm) and TP (73 ± 5 N/mm) tendons. The cross-sectional area of the BPTB tendons was 67 ± 5 mm², of the single-loop tibialis tendons 36 ± 2 mm², of the TA tendons 20 ± 1 mm², and of the TP tendons 23 ± 1 mm². The elongation of the single-loop tibialis tendons and of the BPTB tendons was almost similar (7 ± 0.4 mm). The same applied to the TA and TP tendons (14 ± 0.6 mm). The results of this in vitro mechanical study suggest that fresh-frozen single-loop TA and TP tendons, and BPTB allografts are an acceptable substitute for hamstrings in anterior cruciate ligament reconstruction.     

Age-related changes in the protein and mRNA levels of CYP2E1 and CYP3A isoforms as well as in their hepatic activities in Wistar rats. What role for oxidative stress?

Drug biotransformation and its therapeutic effect may be modified during ageing. Among different causative factors of ageing, the impairment of normal cellular functions by free radicals has been evoked as playing a critical role. The effect of age on the expression and activity of CYP2E1 and CYP3A was investigated in male Wistar rats of 3, 8, 11 and 18 months old. The total cytochrome P450 as well as the expression and the activity (midazolam oxidation) of CYP3A isoforms did not change until 18 months of age. Chlorzoxazone hydroxylation (CYP2E1 activity) increased from 3 to 8 months, remained constant between 8 and 11 months and then progressively decreased until 18 months. Interestingly, CYP2E1 microsomal protein followed the same enzyme activity profile from 3 to 8 months, but remained constant thereafter. The level of CYP2E1 mRNA did not change over the whole period. While the amount of proteins did not change after 8 months, their functionality may be affected by oxidative stress (increase in thiobarbituric acid reactive substances, decrease in reduced glutathione level). However, no changes in carbonyl protein content were observed. The decrease in CYP2E1 activity in rats after 11 months is most probably due to post-translational modifications of CYP2E1 proteins. Indeed, it may be correlated with an accumulation of oxidative damage. Since no change was observed in CYP3A activity or in their protein and mRNA content, it seems that such isoforms should be less affected by oxidative stress.     

Isolation and identification of a new major metabolite of diflunisal in man. The sulfate conjugate

A new metabolite of diflunisal has been identified in volunteers and patients after multiple dose administration. The metabolite was isolated from human urine by silica gel chromatography and was further purified by reversed phase HPLC. Arylsulfatase from Helix pomatia and from Aerobacter aerogenes completely hydrolyzed the isolated metabolite to diflunisal, although hydrolysis by bacterial arylsulfatase was extremely slow. Electron impact mass spectra for diflunisal and its sulfate conjugate were virtually identical. Negative ion fast atom bombardment mass spectra clearly showed the quasimolecular ion [M-H]- at m/z 329 (base peak) as well as a large fragment ion (90% relative intensity) at m/z 249 corresponding to the loss of the sulfate moiety. Urinary excretion patterns in volunteers and rheumatoid arthritis patients revealed that sulfate conjugation of diflunisal is a minor metabolic pathway after single 500-mg dose administration (less than 10% of the dose), whereas it becomes a major pathway (21.3-44.3% of the dose) following multiple doses (500 mg b.i.d.). In one volunteer, who ingested 500 mg diflunisal b.i.d. for 5 weeks, it was shown that the percentage of the dose excreted as diflunisal sulfate gradually increased during the first week to approximately 30% and stayed virtually unchanged for the remaining 4 weeks of diflunisal intake. These preliminary observations are not compatible with the idea that sulfate conjugation is capacity-limited at lower substrate concentrations than glucuronide conjugation, nor do they suggest that sulfation of diflunisal is rate-limited by depletion of inorganic sulfate body stores.