Dissolving Microneedles as Skin Allergy Test Device.

The possibility of using dissolving microneedles (DMs) as a skin allergy test device was studied in rats. Poly-L-arginine was used as a model allergen. Dextran was used to prepare three kinds of DM array chips containing different doses of poly-L-arginine: 17.1±0.5 µg (low-dose DM), 42.2±0.8 µg (medium-dose DM), and 87.4±1.1 µg (high-dose DM); each 1.0 cm2 chip contained 300 DMs. The mean lengths of the low-, medium-, and high-dose DM were 489±3, 485±3, and 492±1 µm and mean diameters of the base were 301±2, 299±1, and 299±2 µm, respectively. Furthermore, for the low-, medium-, and high-dose DM, the administered doses of poly-L-arginine were estimated to be 9.3±1.9, 31.1±1.3, and 61.9±4.7 µg and the scratching behavior per 30 min was 9.8±3.4, 60.4±8.3, and 95.7±10.6 times, respectively. These results demonstrate the dose dependence of the immunoreactivity of the poly-L-arginine DMs, suggesting that DMs can be used an alternative skin allergy device.

Transport of Azithromycin into Extravascular Space in Rats.

Recent clinical trials showed a prolonged retention of subinhibitory concentrations of unbound azithromycin in the interstitial fluid of soft tissues despite the fact that azithromycin is extensively distributed in tissues. In these clinical trials, interstitial fluid samples were obtained by using the microdialysis method, and it was established that drug concentrations represent protein-unbound drug concentrations. The present study was designed to measure total azithromycin concentrations in the interstitial fluid of the skin of rats by directly collecting interstitial fluid samples from a pore formed on the skin by a dissolving microneedle array. The total azithromycin concentrations in interstitial fluid of the skin were about 4 to 5 times higher than those in plasma throughout the experimental period, and stasis of the azithromycin concentration in interstitial fluid was observed when the concentration of azithromycin in plasma was at the lower limit of quantification. In addition, the skin/plasma concentration ratio transiently increased after dosing (from 4.3 to 83.1). Our results suggest that azithromycin was trapped inside white blood cells and/or phagocytic cells in not only blood but also interstitial fluid, resulting in a high total azithromycin concentration and the retention of its antimicrobial activity at the primary infection site. The stasis of azithromycin in interstitial fluid and skin would lead to long-lasting pharmacological effects (including those against skin infection) at concentrations exceeding the MIC.

Therapeutic Drug Monitoring of Vancomycin in Dermal Interstitial Fluid Using Dissolving Microneedles.

OBJECTIVE: To design an alternative painless method for vancomycin (VCM) monitoring by withdrawing interstitial fluid (ISF) the skin using dissolving microneedles (DMNs) and possibly replace the conventional clinical blood sampling method. METHODS: Male Wistar rats were anesthetized with 50 mg/kg sodium pentobarbital. Vancomycin at 5 mg/mL in saline was intravenously administered via the jugular vein. ISF was collected from a formed pore at 15, 30, 45, 60, 75, 90, and 120 min after the DMNs was removed from the skin. In addition, 0.3 mL blood samples were collected from the left femoral vein. RESULTS: The correlation between the plasma and ISF VCM concentrations was significantly strong (r = 0.676, p < 0.05). Microscopic observation of the skin after application of the DMNs demonstrated their safety as a device for sampling ISF. CONCLUSION: A novel monitoring method for VCM was developed to painlessly determine concentrations in the ISF as opposed to blood sampling.

Semi-physiological pharmacokinetic-pharmacodynamic (PK-PD) modeling and simulation of 5-fluorouracil for thrombocytopenia in rats.

1. The aim of this study was to develop a simple pharmacokinetic-pharmacodynamic (PK-PD) model that could characterize the complete time-course of alterations in platelet counts to predict the onset and degree of thrombocytopenia, which severely limits the use of the anticancer agent 5-fluorouracil (5-FU), in rats. 2. Platelet counts were measured in rats following the intravenous administration of various doses of 5-FU for 4 days to obtain data for an analysis of the PK-PD model. Our PK-PD model consisted of a two-compartment PK model, with three compartments for the PD model and 10 structural PK-PD model parameters. 3. After the 5-FU treatment, platelet counts transiently decreased to a nadir level, showed a rebound to above the baseline level before recovering to baseline levels. Nadir platelet counts and rebounds varied with the AUC0-∞ level. The final PK-PD model effectively characterized platelet count data and final PD parameters were estimated with high certainty. 4. This PK-PD model and simulation may represent a valuable tool for quantifying and predicting the complete time-course of alterations in blood cell counts, and could contribute to the development of therapeutic strategies with 5-FU and assessments of various novel anticancer agents that are difficult to examine in humans.

Application of dissolving microneedles to glucose monitoring through dermal interstitial fluid.

Dissolving microneedles (DMs) were applied to glucose monitoring in the dermal interstitial fluid (ISF) of rats and their potential as an alternative blood glucose monitoring device was evaluated. Sodium chondroitin sulfate was used to prepare DM array chips, which consisted of 300 DMs/cm(2). The mean length of the DMs was 475±18 µm and the mean diameter of the basement was 278±8 µm. After DMs were inserted into the skin of the hair-removed rat abdomen, a wet unwoven cloth containing 10-30 µL of water was placed on the skin and ISF was extracted. By increasing the absorbed amount of water on the unwoven cloth from 10 to 30 µL, the extracted amount of glucose increased from 1.66±0.35 µg to 2.75±0.61 µg. Increasing the adhesion time of the wet unwoven cloth to the skin from 0.1 to 5.0 min, increased the amount of ISF glucose from 1.99±0.13 µg to 5.04±0.38 µg. The relation between the amount of glucose in ISF and blood glucose concentrations was examined. With increase in the adhesion time, the coefficient of determination, r(2), increased from 0.501 to 0.750. The number of DMs also affected the relationship and values of the coefficient of determinations, r(2) were: 0.340 (25 DMs), 0.758 (50 DMs), 0.763 (100 DMs), 0.774 (200 DMs), and 0.762 (300 DMs). These results indicate the usefulness of DMs as an alternative blood glucose monitoring device.

Semi-physiological pharmacokinetic-pharmacodynamic modeling and simulation of 5-fluorouracil for the whole time course of alterations in leukocyte, neutrophil and lymphocyte counts in rats.

We aimed to develop a simple pharmacokinetic-pharmacodynamic (PK-PD) model to predict the onset and degree of severe toxic side effects that severely limit the use of many anticancer agents, such as myelosuppression, in rats. Our PK-PD model consisted of a two-compartment PK model, with one compartment representing proliferative cells and some transit compartments consisting of maturing cells, while the other compartment represented circulating blood cells for the PD model. The semi-physiological PK-PD model effectively captured the features of myelosuppression and the degree of the off-target toxicities observed after 5-fluorouracil (5-FU) chemotherapy, and helped simultaneously simulate the whole time course for alterations in leukocyte, neutrophil and lymphocyte counts after 5-FU treatment in rats. Interestingly, by plotting the nadir period of leukocyte, neutrophil and lymphocyte counts as determined by PK-PD analytical simulation curves against the area under the plasma 5-FU concentration-time curve (AUC0-∞) after intravenous administration of 5-FU, a linear relationship was inferred, with r2=0.989, 0.877 and 0.956, respectively. The semi-physiological PK-PD model is a valuable tool for evaluating a variety of novel cancer chemopreventive agents or emerging therapeutic strategies that are difficult to address in humans.

Pre-therapeutic assessment of plasma dihydrouracil/uracil ratio for predicting the pharmacokinetic parameters of 5-fluorouracil and tumor growth in a rat model of colorectal cancer.

We investigated the correlation between plasma ratio of dihydrouracil/uracil (UH2/Ura), a possible surrogate biomarker of hepatic dihydropyrimidine dehydrogenase (DPD) activity, and 5-fluorouracil (5-FU) treatment efficacy in rats with colorectal cancer (CRC). 5-FU pharmacokinetic and pharmacodynamic studies were performed using DPD circadian variation in rats with 1,2-dimethylhydrazine-induced CRC. By plotting tumor volume after 5-FU treatment against pre-therapeutic plasma UH2/Ura, we inferred a linear relationship (r(2)=0.988). 5-FU concentration fluctuations induced by DPD activity variation affected tumor volume. In CRC patients receiving proper dosing regimens, plasma UH2/Ura could be an indirect biomarker for predicting 5-FU treatment efficacy, tumor growth, and 5-FU doses.

A predictive biomarker for altered 5-fluorouracil pharmacokinetics following repeated administration in a rat model of colorectal cancer.

The relationship between the plasma ratio of dihydrouracil/uracil (UH2/Ura) and hepatic dihydropyrimidine dehydrogenase (DPD) activity after repeated 5-fluorouracil (5-FU) treatment in rats with colorectal cancer (CRC) was investigated. Repeated intravenous 5-FU bolus injections resulted in a significant decrease in the total clearance (CLtot ) and an increased area under the curve (AUC0-∞ ) in CRC rats. Furthermore, the hepatic DPD levels and the plasma ratio of UH2/Ura decreased significantly and lost their circadian rhythms in CRC rats treated repeatedly with 5-FU, although significant circadian variation in the two parameters was observed in the control CRC rats. Moreover, a significant correlation was found between the plasma ratio of UH2/Ura and hepatic DPD activity in CRC rats untreated and treated with single or repeated 5-FU administration (r(2) = 0.865, p < 0.01). The ratio of UH2/Ura in plasma could be a predictive biomarker of the suppression of hepatic DPD levels during repeated 5-FU-based treatment. Furthermore, by plotting the observed pharmacokinetic parameters of 5-FU against hepatic DPD activity levels predicted by the ratio of UH2/Ura in plasma, AUC0-∞ , CLtot and half-life (t1/2 ) were closely linked to predicted hepatic DPD activity levels. These observations suggest that the factor that significantly influences the AUC0-∞ , CLtot and t1/2 of 5-FU after single or repeated administration of 5-FU is the hepatic DPD activity and it could be assessed by the ratio of UH2/Ura in plasma.

Method to increase the systemically delivered amount of drug from dissolving microneedles.

To increase the absorbed amount of a drug from dissolving microneedles (DMs), three DM array chips were prepared in which (1) the drug was localized at the acral portion of DMs, (2) the drug was loaded in each whole DM, and (3) the drug was loaded in DMs and the chip. Fluorescein free form (FL) and its sodium salt (FLNa) were used as model drugs. The DM array chip had 15-mm diameter with 225 DMs, each 500-µm long with a 300-µm diameter base. The respective FLNa contents in the three chips were (1) 0.18±0.03, (2) 0.64±0.07, and (3) 10.95±1.07 mg. The FL contents were (1) 0.20±0.01, (2) 0.68±0.03 and (3) 12.47±1.01 mg. The in vitro release of fluorescein from FLNa DMs was faster than that from FL DMs. In vitro permeability experiments showed that (3) produced the greatest increase in the permeability of fluorescein through rat skin, especially in FLNa loaded DMs. In vivo rat absorption study by application of DM array chips to the rat abdominal skin for 6 h demonstrated that the systemically absorbed amount of fluorescein increased from 0.18±0.02 mg, 0.53±0.19 mg, to 5.38±1.99 mg from systems (1) and (2)-(3). By decreasing the application time of DMs to the rat skin, the absorbed amount of fluorescein decreased along with the application time. The physiological state of the skin recovered within 30 min after chip removal. Using a type (3) DM array chip, more than 1.0 mg of water-soluble drug can be delivered to the systemic circulation.

Pharmacokinetics of 5-fluorouracil and increased hepatic dihydropyrimidine dehydrogenase activity levels in 1,2-dimethylhydrazine-induced colorectal cancer model rats.

To investigate the hepatic dihydropyrimidine dehydrogenase (DPD) activity in colorectal cancer (CRC), which is critically important to create a patient-specific dosing regimen, we performed 5-FU pharmacokinetic studies in 1,2-dimethylhydrazine-induced CRC model rats (CRC rats). After rats received 5-FU intravenous (IV) bolus injections, the area under the plasma concentration-time curve (AUC) and elimination half-life (t 1/2) in CRC rats (10.02 ± 0.37 µg h mL(-1), 0.30 ± 0.02 h, respectively) were significantly lower than that in control rats (13.46 ± 1.20 µg h mL(-1), 0.52 ± 0.05 h, respectively), whereas total plasma clearance (CLtot) in CRC rats (2.01 ± 0.07 L h(-1) kg(-1)) was significantly increased compared with that in control rats (1.54 ± 0.14 L h(-1) kg(-1)). Conversely, the avoidance ratio of the hepatic first-pass effect was approximately 20 % lower than that in control rats. Of interest is that hepatic DPD activity levels and the dihydrouracil-uracil ratio (UH2/Ura ratio) in plasma, which may act as a potential biomarker to evaluate hepatic DPD activity levels, were significantly increased in CRC rats. These results suggest that the decrease of hepatic availability in CRC rats is brought about by the increase in intrinsic clearance induced by the increase in DPD activity, resulting in a decrease in AUC and t 1/2 and an increase in CLtot after 5-FU IV bolus injection. Along with a proper dosing regimen for patients with CRC, a hepatic DPD activity monitoring system, such as the determination of UH2/Ura ratio in plasma, is desirable.

Two-layered dissolving microneedles for percutaneous delivery of peptide/protein drugs in rats.

PURPOSE: Feasibility study of two-layered dissolving microneedles for percutaneous delivery of peptide/proteins using recombinant human growth hormone (rhGH) and desmopressin (DDAVP). METHODS: Two-layered dissolving microneedles were administered percutaneously to the rat skin. Plasma rhGH and DDAVP concentrations were measured by EIA and LC/MS/MS. In vivo dissolution and diffusion rates of drugs in the skin were studied using tracer dyes, lissamine green B (LG) for rhGH and evans blue (EB) for DDAVP. Diffusion of drugs vertically into the skin was studied using FITC-dextran (MW = 20 kDa)-loaded dissolving microneedles. Stability experiments were performed at -80°C and 4°C. RESULTS: The absorption half-lives, t (1/2a), of rhGH and DDAVP from dissolving microneedles were 23.7 ± 4.3-28.9 ± 5.2 and 14.4 ± 2.9-14.1 ± 1.1 min; the extents of bioavailability were 72.8 ± 4.2-89.9 ± 10.0% and 90.0 ± 15.4-93.1 ± 10.3%, respectively. LG and EB disappeared from the administered site within 2 h and 3 h after administration. Five green fluorescein spots were detected at 15 s and enlarged transversally at 30 s. FITC-dextran was delivered into the microcapillaries at 5 min and 10 min. The rhGH and DDAVP were stable in dissolving microneedles for one month at -80°C and 4°C. CONCLUSIONS: Results suggest that the two-layered dissolving microneedles are useful as an immediate-release transdermal DDS for peptide/protein drugs.

Utility of nano-sized, water-in-oil emulsion as a sustained release formulation of glycyrrhizin.

The aim of this study was to determine the efficiency of nano-sized water-in-oil (w/o) emulsions that encapsulate glycyrrhizin (GZ) (Rp-I) as a sustained release formulation for subcutaneous administration. Four formulations were assessed in rats for 8-72 h: nano-sized water-in-oil (w/o) emulsion encapsulating GZ (Rp-I), GZ aqueous solution (Rp-II), oil-in-water (o/w) emulsion containing GZ (Rp-III), and w/o emulsion containing solid GZ (Rp-IV). All had a GZ concentration of 150 mg/ml. Over an 8-h period, GZ elimination in bile after subcutaneous administration of Rp-I, Rp-II, Rp-III, and Rp-IV (50 mg/kg GZ) was 10.8%, 97.0%, 81.0%, and 7.1%, respectively. The elimination of GZ into bile after the administration of Rp-IV was the lowest (30.5%) at the 72-h endpoint, dropping significantly from 48 to 72 h. On the other hand, the elimination rate of GZ after the administration of Rp-I was sustained at a constant level (1.8-2.1 mg/24 h) over 72 h. GZ concentration in liver at 72 h in Rp-I was highest (19.9 µg/g tissue) among the four formulations, suggesting that the release of GZ from the Rp-I formulation is constant, at least up to 72 h after administration. These results suggest that a nano-sized w/o emulsion is useful as a sustained release formulation for long-term therapy of chronic hepatitis.

Decrease in brain distribution of fluvoxamine in experimental hyperlipidemic rats.

PURPOSE: Many clinical reports and trials have suggested that fluvoxamine (FLV) reduces plasma lipoprotein levels. However, few studies have reported the effect of plasma lipoproteins on FLV pharmacokinetics. The aim of the present study was to investigate the affinities of FLV to plasma lipoproteins and the effect of plasma lipoproteins on the biodistribution of FLV using an experimental hyperlipidemic (HL) rat model. METHODS: HL rats were prepared by intraperitoneal administration of Poloxamer-407 solution (1.0 g/kg). In vitro protein binding and distribution of FLV in plasma lipoproteins were determined in control and HL rats. In vivo pharmacokinetic study (intravenous administration of FLV, 5.0 mg/kg) and biodistribution analysis for brain and liver at a steady state (infusion, 1.5 mg/kg/hr, 6 hrs) were also performed. RESULTS: The plasma protein binding of FLV was around 83% and 95% in control and HL rats, respectively, whereas the FLV recoveries in triglyceride-rich lipoprotein fractions were increased in HL. Therefore, the elevation of lipoproteins was likely responsible for the increase in protein binding in HL. After intravenous administration, the area under the plasma concentration vs. time curve (AUC) in HL was 3.9-fold greater than that in control rats, whereas the distribution ratio of FLV plasma concentration to the brain at a steady state was decreased to approximately 20% of that of the control. CONCLUSIONS: FLV has an affinity to plasma lipoproteins, and their elevation might decrease the FLV biodistribution to brain; the plasma lipoprotein levels could not be found to correlate positively with the FLV pharmacokinetic effect in brain, but rather may attenuate it.

Two-layered dissolving microneedles for percutaneous delivery of sumatriptan in rats.

A novel transdermal delivery of sumatriptan (ST) was attempted by application of dissolving microneedle (DM) technology. Dextran DM (d-DM) and hyaluronate DM (h-DM) were prepared by adding ST solution to dextran solution or hyaluronic acid solution. One DM chip, 1.0 × 1.0 cm, contains 100 microneedle arrays in a 10 × 10 matrix. The mean lengths of DMs were 496.6 ± 2.9 µm for h-DM and 494.5 ± 1.3 µm for d-DM. The diameters of the array basement were 295.9 ± 3.9 µm (d-DM) and 291.7 ± 3.0 µm (h-DM), where ST contents were 31.6 ± 4.5 µg and 24.1 ± 0.9 µg. These results suggest that ST was stable in h-DM. Each DM was administered to rat abdominal skin. The maximum plasma ST concentrations, Cmax, and the areas under the plasma ST concentration versus time curves (AUC) were 44.6 ± 4.9 ng/ml and 24.6 ± 3.9 ng · h/ml for h-DM and 38.4 ± 2.7 ng/ml and 14.1 ± 1.5 ng · h/ml for d-DM. The bioavailabilities of ST from DMs were calculated as 100.7 ± 18.8% for h-DM and 93.6 ± 10.2% for d-DM. Good dose dependency was observed on Cmax and AUC. The stability study of ST in DM was performed for 3 months under four different conditions, −80, 4, 23, and 50°C. At the end of incubation period, they were, respectively, 100.0 ± 0.3%, 97.8 ± 0.2%, 98.8 ± 0.2%, and 100.7 ± 0.1%. These suggest the usefulness of DM as a noninvaisive transdermal delivery system of ST to migraine therapy.

Polymeric three-layered particles for the delivery of prednisolone to the lower gastrointestinal tract in rats.

BACKGROUND: The aim of this study is to investigate the feasibility of three-layered particles as a drug delivery system to the lower part of small intestine. METHODS: The particle surface and basement layers were made of enteric polymer, Eudragit(®) S100, and water-insoluble polymer, ethylcellulose. Prednisolone (PSL), as a model drug, was sealed with the surface and basement layers. After the administration of the test preparations to the duodenum of rats, blood samples were collected and plasma PSL levels were measured by high-performance liquid chromatography. The retention and transit characteristics of the three-layered particles in rat small intestine were studied by direct observation after abdominal incision up to 8 hours. RESULTS: Three-layered PSL particles showed C(max) of 0.32 ± 0.07 µg/mL and T(max) at 6 hours, whereas the mean C(max) and T(max) of PSL powder, as a reference preparation, were 0.42 ± 0.03 µg/mL and 1 hour, respectively. With the direct observations, after administration of particles, about 77.5% of them were detected in duodenum at 1 hour, 45% in distal jejunum at 3 hours, and 50% in proximal ileum at 4 hours. Then, they were gradually transferred to the lower part of the small intestine at 5-8 hours time intervals. In comparison with PSL powder, three-layered particles delayed the intestinal transit and released PSL during their passage through the small intestine. CONCLUSION: These results suggested that three-layered particles adhered to the gastrointestinal mucosa and sustained the release of drug, resulting in drug delivery to the lower part of gastrointestinal tract.

Self-dissolving micropile array chip as percutaneous delivery system of protein drug.

Erythropoietin (EPO) was successfully loaded on self-dissolving micropile array (SDMA) chip using chondroitin sulfate as the base polymer. "Drug glue" was prepared by adding EPO solution to chondroitin sulfate solution and SDMA was formed by micromolding fabrication technology. One SDMA chip, 1.0x1.0 cm, contained 100 micropile arrays. Two types of SDMA, partially-loaded SDMA (p-SDMA) and fully-loaded SDMA (f-SDMA), were prepared. The mean lengths of the SDMAs were 474.8+/-8.1 microm for p-SDMA and 473.4+/-5.2 microm for f-SDMA. The diameters of the array basements were 288.4+/-4.5 microm (p-SDMA) and 294.6+/-3.2 microm (f-SDMA). EPO content was 25.0+/-3.8 IU (p-SDMA) and 125.9+/-26.7 IU (f-SDMA). After percutaneous administration of each SDMA chip to rats, maximum serum EPO concentrations (C(max)) were 30.5+/-4.2 mIU/ml for p-SDMA and 32.4+/-5.0 mIU/ml for f-SDMA. The mean areas under the serum EPO concentration vs. time curves (AUC) were 534.0+/-102.4 mIU.h/ml (p-SDMA) and 523.1+/-50.4 mIU.h/ml (f-SDMA). Bioavailability (BA) values of EPO delivered from SDMAs were calculated to be 39.4% for p-SDMA and 7.7% for f-SDMA. Dose-dependency of the serum EPO concentration vs. time curve was studied using p-SDMA chip containing less EPO, 11.6+/-1.06 IU. Good dose-dependency was observed for C(max) and AUC. The p-SDMA chip was also evaluated in dogs. One or two p-SDMA chips, where 1 chip contained 22.4 IU of EPO, were percutaneously administered to dogs. BA of EPO delivered from p-SDMA was 65.9-69.0%. These results suggest the usefulness of p-SDMA as a percutaneous drug delivery system (DDS) for EPO.

Self-dissolving micropile array tips for percutaneous administration of insulin.

Two kinds of insulin were loaded into self-dissolving micropile array tip (following tip). Fully-loaded tip (f-tip) and partially-loaded tip (p-tip) were prepared using chondroitin sulfate for the percutaneous administration of insulin. One hundred micropiles were constructed on a 1.0 x 1.0 cm tip. The mean length of the micropile in a tip were 483.4 +/- 4.7 mum for the f-tip and 492.6 +/- 2.4 mum for the p-tip. The insulin content of the p-tip was 28.5% of that of the f-tip. The pharmacological efficiency of insulin loaded tip was evaluated in rat experiments by measuring their hypoglycemic effects. The maximum hypoglycemic effect of insulin was observed at 1.7 +/- 0.2 h for the f-tip and 1.5 +/- 0.2 h for the p-tip. Good dose-dependency was observed for the plasma glucose level vs. time curves. These results suggest the usefulness of p-tip as a percutaneous DDS of insulin.

Permeation enhancement of ascorbic acid by self-dissolving micropile array tip through rat skin.

Ascorbic acid (AA) loaded self-dissolving micropiles (SDMP) were prepared using chondroitin sulfate as the base for the percutaneous administration of AA. AA solution was added to dense solution of chondroitin solution, glue, and array tip, 1.0 cm(2), containing 100 SDMPs of which length was 500 microm and basal diameter was 300 microm, were prepared. Two kinds of AA array tips containing 1344.2+/-1.7 microg (high content ones) and 638.7+/-4.3 microg (low content ones) were used. In vitro dissolution study showed that more than 90% of AA were released from both SDMP array tips within 5 min. Stability experiment showed that 99.2-99.4% of AA was detected in SDMP array tips when stored at 23 degrees C for 1 week. When in vitro permeation experiments were performed after AA SDMP array was inserted to the isolated rat abdominal skin, extremely high amounts of AA, 1285.3+/-369.0 microg (95.3%) for high content SDMP tip and 405.6+/-84.3 microg (65.8%) for low content SDMP tip, were permeated for 6 h into the receptor compartment due to the break down of the skin barrier function. When AA SDMP array tip was administered to the rat skin under anesthetized condition with the different contact times, 10, 20 and 30 min, the permeated amount of AA was dependent on both the AA content in SDMP array tips and the contact time. When AA SDMP was contact to the skin for 30 min, permeated amounts of AA were 146.8+/-22.9 microg (10.9%) for high content-SDMP tip and 61.2+/-18.2 microg (9.6%) for low content SDMP tip. These results suggest the usefulness of SDMP array tip for the percutaneous absorption of AA.

Molecular weight dependence on bioavailability of FITC-dextran after administration of self-dissolving micropile to rat skin.

BACKGROUND: Self-dissolving micropiles (SDMPs) have been evaluated with macromolecular drugs like insulin and erythropoietin as a new percutaneous drug delivery system. To study the molecular weight dependence on the absorption of macromolecular drugs through the skin after administration of SDMPs, four kinds of SDMP were prepared using fluorescein isothiocyanate-labeled dextrans (FDs) having a molecular weight of 10, 20, 40, and 70 kDa. METHOD: In in vitro release experiments there were no significant differences on their release rates in the four SDMPs. The dependence of molecular weight of FD on the permeability coefficient was studied in the in vitro permeation experiment. Histological study on the skin after administration of FD SDMP (5.0 mg/kg) to rat was performed for 24 hours. In vivo experiment using rats resulted in slower absorption rate of FD-40 and FD-70 SDMP (5.0 mg/kg). RESULTS: The permeability coefficient was 4.59, 4.69, 3.38, and 1.43 x 10(-4) cm/h for FD-10, 20, 40, and 70, respectively. Histological examination showed that yellow color was still observed at 6 h after administration of FD-40, and FD-70 showed yellow color even at 24 h. Bioavailabilities of FDs from SDMP were 99.4 +/- 6.93%, 88.3 +/- 7.05%, 45.7 +/- 4.77%, and 16.0 +/- 1.15% for FD-10, 20, 40, and 70, and the dependency on molecular weight dependence was clearly observed. CONCLUSION: These observations supported that bioavailabilities of FD from SDMP decreased as the molecular weight of FD increased to more than 40 kDa.

Effects of obesity induced by high-fat diet on the pharmacokinetics of nelfinavir, a HIV protease inhibitor, in laboratory rats.

The effect of obesity induced by a high-fat diet on the pharmacokinetics (PK) of nelfinavir (NFV) was investigated, focusing on the change of distribution and elimination caused by dyslipidemia and hepatic steatosis.The plasma unbound fraction (f(u)) of NFV in obese rats (0.61+/-0.03%) was significantly lower than in the control (1.10+/-0.09%), caused by increasing the plasma triglyceride-rich lipoprotein level. After intravenous (i.v.) administration of NFV, the marked decrease of the distribution volume and slower total clearance (39.5% and 69.1% of the control, respectively) caused by the lower f(u) were the main reasons for the significantly higher area under the blood concentration versus time curve (AUC) in obese rats (145.3% of the control). The absorption of NFV after intraduodenal (i.d.) administration in obese rats was significantly greater than in the control (AUC; 170.4% of the control). The increased bile in obese rats was the main reason for the increasing absorption of NFV, and the lower expression of intestinal P-glycoprotein was also considered. On the other hand, although higher AUCs in obese rats were shown, unbound AUCs in the obese rats were slightly lower than in the control, namely, the plasma NFV concentration in obese rats to obtain the same pharmacological effect was higher than in the control, suggesting the difficulty of drug monitoring. These results suggest that it is necessary to pay further attention to therapeutic drug monitoring of NFV in patients manifesting metabolic syndrome, such as dyslipidemia and visceral fat accumulation, including hepatic steatosis.