Transdermal delivery of diclofenac using microemulsions

A transdermal preparation containing diclofenac diethylammonium (DDA) was developed using an O/W microemulsion system. Of the oils tested, lauryl alcohol was chosen as the oil phase of the microemulsion, as it showed a good solubilizing capacity and excellent skin permeation rate of the drug. Pseudoternary phase diagrams were constructed to obtain the concentration range of oil, surfactant and cosurfactant for microemulsion formation, and the effect of these additives on skin permeation of DDA was evaluated with excised rat skins. The optimum formulation of the microemulsion consisted of 1.16% of DDA, 5% of lauryl alcohol, 60% of water in combination with the 34.54% of Labrasol (surfactant)/ethanol (cosurfactant) (1:2). The efficiency of formulation in the percutaneous absorption of DDA was dependent upon the contents of water and lauryl alcohol as well as Labrasol:ethanol mixing ratio. It was concluded that the percutaneous absorption of DDA from microemulsions was enhanced with increasing the lauryl alcohol and water contents, and with decreasing the Labrasol:ethanol mixing ratio in the formulation.     

Transdermal iontophoretic delivery of diclofenac sodium from various polymer formulations: in vitro and in vivo studies

The objective of this study was to evaluate the in vitro and in vivo transdermal iontophoresis of various diclofenac sodium polymer formulations. The excised rat skin, human skin as well as cellulose membrane were used to examine the in vitro drug permeation whereas the microdialysis technique was used to monitor the drug concentration in vivo. Polymer solutions based on polyvinylpyrrolidone (PVP) and hydroxypropyl methylcellulose (HPMC) binary system showed higher drug permeability than that of single polymer vehicle. The effect of formulations on drug permeation through cellulose membrane was quite different from those through rat skin and human skin, which can be explained by the different permeation pathways between them. It appeared to be a membrane-controlled mechanism but not the vehicle matrix-controlled mechanism for diclofenac hydrogels when using skin as the diffusion barrier. The recovery of diclofenac sodium in the in vivo microdialysis was approximately 80-90%, indicating this technique can be used in the intradermal drug monitoring. For all the polymer formulations tested, there was a good relationship between the in vitro and in vivo drug permeation. A synergistic effect on drug permeation was observed when transdermal iontophoresis combined with the pretreatment of cardamom oil as a permeation enhancer.     

The antidiabetic effect of ginsenoside Rb2 via activation of AMPK

Ginsenosides, which are active compounds found in ginseng (Panax ginseng), are used as antidiabetic treatments. The aim of this study was to determine whether Rb2, a type of ginsenoside, regulates hepatic gluconeogenesis through AMP-activated protein kinase (AMPK) and the orphan nuclear receptor small heterodimer partner (SHP) in hyperlipidemic conditions used as an in vitro model of type 2 diabetes. Considering these results, we concluded that Rb2 may inhibit palmitate-induced gluconeogenesis via AMPK-induced SHP by relieving ER stress, a cause of gluconeogenesis.     

Transdermal delivery of antidiabetic drugs: formulation and delivery strategies

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Targeted delivery of diclofenac sodium via gelatin magnetic microspheres formulated for intra-arterial administration

In the present work, we have attempted to deliver diclofenac sodium to a target site by intra-arterial injection of gelatin magnetic microspheres and subsequent localization using an external magnet. Drug-loaded magnetic microspheres were prepared by emulsification/cross-linking method, characterized by drug loading, magnetite content, size distribution, optical microscopy, scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) analysis, differential scanning calorimetry (DSC), X-ray diffraction (XRD), absence of glutaraldehyde by gas chromatography, and in vitro release studies. The targeting efficiency and the therapeutic efficacy of microspheres were studied in vivo in rabbits. The microspheres showed drug loading of 9.1, 18.7, 24.9% w/w, magnetite content of 27.8–28.9% w/w with an average size range of 25–30.6 μm, depending upon the drug–polymer ratio. They were spherical in nature as evidenced by optical microscopy and SEM. FT-IR, DSC, and XRD studies revealed the absence of drug–polymer interaction. Gas chromatography confirmed the absence of residual glutaraldehyde. The microspheres were able to prolong the drug release over 24–30 days and the application of sonication during in vitro release study has slightly increased the release rate. After intra-arterial administration of microspheres, 77.7% of injected dose was recovered at the target site which revealed good targeting efficiency. The microspheres effectively reduced joint swelling, but lesser extent than the oral diclofenac sodium in high dose, in antigen induced arthritic rabbits without producing gastric ulceration which was observed in rabbits treated with oral diclofenac sodium.     

Ultrasonically controlled release and targeted delivery of diclofenac sodium via gelatin magnetic microspheres

In the present work, an attempt was made to target diclofenac sodium to its site of action through magnetic gelatin microspheres. The gelatin magnetic microspheres loaded with 8.9% w/w of diclofenac sodium and 28.7% w/w of magnetite were formulated by emulsification/cross-linking with glutaraldehyde. The formulated microspheres were characterized by particle size distribution, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), X-ray diffraction and in vitro release studies. The in vivo distribution and targetability of gelatin magnetic microspheres after i.v. administration were studied in rabbits. The formulated microspheres were below 5 microm and spherical in nature as evidenced by the SEM photographs. DSC and X-ray diffraction studies revealed the absence of drug-polymer interaction. Encapsulated diclofenac sodium was released slowly more than 18 days. Application of sonication, as external stimuli to enhance drug release, during release study, has slightly increased the release rate. The formulated microspheres were injected intravenously after keeping a suitable magnet near the target area. The quantity of drug available at the target and non-target area was determined by HPLC. About 5.5% of injected dose localized near the target organ. Majority of injected dose was recovered from lungs, spleen and liver indicating localization of microspheres in these organs. Further studies are required to improve the targeting efficiency of gelatin microspheres by modifying surface properties to overcome phagocytosis and by selecting suitable particle size to avoid the entrapment of microspheres in non-target organs.     

Transdermal delivery of methotrexate: iontophoretic delivery from hydrogels and passive delivery from microemulsions

In vitro assays were performed to investigate the effectiveness of transdermal administration of methotrexate (MTX) by iontophoretic delivery from two types of hydrogel and passive delivery from two types of microemulsion. Both iontophoretic delivery of MTX from hydrogels and passive delivery from microemulsions were more effective than passive delivery from aqueous solutions of the drug. In the iontophoretic delivery assays, the type of hydrogel used and the concentration of the drug in the loading solution had little influence on effectiveness of delivery. In the passive delivery assays, we used both water/oil (w/o) and oil/water (o/w) microemulsions: effectiveness of delivery was higher from o/w systems. At the end of all assays, significant amounts of MTX were detected in the skin. These results suggest that both hydrogels and microemulsions may be of value for the topical administration of MTX in the treatment of psoriasis.     

Resveratrol attenuates lipopolysaccharide-induced dysfunction of blood-brain barrier in endothelial cells via AMPK activation

Resveratrol, a phytoalexin, is reported to activate AMP-activated protein kinase (AMPK) in vascular cells. The blood-brain barrier (BBB), formed by specialized brain endothelial cells that are interconnected by tight junctions, strictly regulates paracellular permeability to maintain an optimal extracellular environment for brain homeostasis. The aim of this study was to elucidate the effects of resveratrol and the role of AMPK in BBB dysfunction induced by lipopolysaccharide (LPS). Exposure of human brain microvascular endothelial cells (HBMECs) to LPS (1 µg/ml) for 4 to 24 hours week dramatically increased the permeability of the BBB in parallel with lowered expression levels of occluding and claudin-5, which are essential to maintain tight junctions in HBMECs. In addition, LPS significantly increased the reactive oxygen species (ROS) productions. All effects induced by LPS in HBVMCs were reversed by adenoviral overexpression of superoxide dismutase, inhibition of NAD(P) H oxidase by apocynin or gain-function of AMPK by adenoviral overexpression of constitutively active mutant (AMPK-CA) or by resveratrol. Finally, upregulation of AMPK by either AMPK-CA or resveratrol abolished the levels of LPS-enhanced NAD(P)H oxidase subunits protein expressions. We conclude that AMPK activation by resveratrol improves the integrity of the BBB disrupted by LPS through suppressing the induction of NAD(P)H oxidase-derived ROS in HBMECs.     

Transdermal delivery of salbutamol sulphate: Formulation and evaluation

Salbutamol patches were prepared and evaluated. The effect of different Eudragits and various plasticizers on the properties of the patches were studied. Patches were prepared by casting method employing different plasticizers. These patches were evaluated for weight, thickness uniformity, swelling index, tensile strength, elongation percent and moisture absorption capacity. Release was studied. Tensile strength of the patches using Eudragit RS 100 as well as RS100 + L100 and triacetin was the lowest. Formulae containing 10% oleic acid and 5% dimethyl formamide, respectively, showed the highest permeability. These two formulae were studied clinically, the first formula only showed a significant improvement.     

Transdermal delivery of bupranolol: Pharmacodynamics and beta-adrenoceptor occupancy

Summary Bupranolol is a non-selective beta-adrenoceptor antagonist with a K_i-value of 6–15 nmol/l (equivalent to 1.5–4 ng/ml in plasma) at beta₁- (rat salivary gland) and beta₂-adrenoceptors (rat reticulocytes) in receptor binding studies with³H-CGP 12177 in the presence of human plasma. After oral administration of 200 mg bupranolol to healthy volunteers, the maximal plasma concentration was observed within 1.2 h but it only reached a level close to the K_i-value. Elimination from plasma was rapid (t_1/2=2.0 h).Administration of 30 mg bupranolol in a transdermal delivery system (TTS) every 24 h to 6 healthy volunteers for 72 h yielded steady state plasma concentrations 4- to 5-times above the K_i-value as shown by in vitro inhibition of beta-adrenoceptor binding by plasma samples. The pharmacodynamic effect, measured as the reduction in exercise tachycardia, showed a stable inhibitory effect; antagonism of a bolus injection of isoprenaline indicated a 10- to 15-fold right shift of the dose-response curve during the observation period of 72 h.It is concluded that steady-state plasma concentrations and effect of the elsewise rapidly eliminated beta-blocker bupranolol can be achieved by a transdermal delivery system applied each day.Some of the results were presented at the joint meeting of the Belgian, Dutch and German Pharmacological Societies. September 1985, Aachen (Naunyn-Schmiedebergs Arch Pharmacol 330 [Suppl]: R 64The paper is dedicated to Prof. Dr. H. Oelschläger (Frankfurt am Main, FRG) on occasion of his 65th birthday     

Transdermal delivery of naloxone: ex vivo permeation studies

The purpose of this investigation was to study the feasibility of transdermal drug delivery of the potent opioid antagonist naloxone. The pharmacokinetic profile of naloxone makes it a suitable candidate for transdermal delivery. Ex vivo permeation of naloxone through excised rat skin was studied using a diffusion cell. Radiochemical assay of drug concentration and the use of rat as an animal model were adopted in this study. Naloxone possesses characteristics favorable to percutaneous absorption: i.e. a low molecular weight (327.37), water solubility and a good lipid-water partition coefficient of 12.94+/-1.29 at pH 7.4. The flux (microg/cm2/h) values varied from 6.59+/-0.72 in control to 27. 18+/-4.26 in dimethyl formamide. The affinity of naloxone to skin in the presence of propylene glycol was decreased by 6.2 times compared to the control. Fourier transform infrared spectroscopy was used to study the effect of various sorption promoters on intercellular lipid pathways in skin. A change in lipid fluidization corresponding to broadening for both C-H symmetric (near 2850 cm-1) and C-H asymmetric (near 2920 cm-1) stretching was observed. An attempt was made to correlate the molecular weight of sorption promoters with skin affinity values of naloxone.Copyright     

Transdermal delivery of levonorgestrel. IV: Evaluation of membranes

A series of experiments were performed to evaluate the flux of levonorgestrel (LN), ethyl acetate (EtAc), and ethanol (EtOH) through excised rat skin, through a variety of synthetic membranes and through membranes supported on rat skin. Using a donor phase of EtAc:EtOH (7:3) containing excess solid LN, the flux of LN through rat skin was approximately 1.0 microgramc/cm2.h. The normalized fluxes of LN, EtAc, and EtOH through ethylene vinyl acetate (EVAc) copolymers of varying vinyl acetate (VAc) content (12 to 25%) were 1.3 to 3.1 x 10(-8), 2.6 to 6.8 x 10(-4), and 4.8 to 9.9 x 10(-5) g.cm/cm2.h, respectively. Permeability experiments were also performed with the EVAc membranes supported on rat skin. By selecting the VAc content and thickness of the EVAc membranes, it was possible to control the delivery of enhancer (EtAc:EtOH) through rat skin (membrane-rate control) or to let the skin control the overall delivery of enhancer.     

Transdermal drug delivery using microemulsion and aqueous systems: influence of skin storage conditions on the in vitro permeability of diclofenac from aqueous vehicle systems

The objective of this study was to evaluate the transdermal delivery potential of diclofenac-containing microemulsion system in vivo and in vitro. It was found that the transdermal administration of the microemulsion to rats resulted in 8-fold higher drug plasma levels than those obtained after application of Voltaren Emulgel. After s.c. administration (3.5 mg/kg), the plasma levels of diclofenac reached a peak of 0.94 microg/ml at t=1 h and decreased rapidly to 0.19 microg/ml at t=6 h, while transdermal administration of the drug in microemulsion maintained constant levels of 0.7-0.9 microg/ml for at least 8 h. The transdermal fluxes of diclofenac were measured in vitro using skin excised from different animal species. In three rodent species, penetration fluxes of 53.35+/-8.19 (furry mouse), 31.70+/-3.83 (hairless mouse), 31.66+/-4.45 (rat), and 22.89+/-6.23 microg/cm(2)/h (hairless guinea pig) were obtained following the application of the microemulsion. These fluxes were significantly higher than those obtained by application of the drug in aqueous solution. In contrast to these results, a 'flip-flop' phenomenon was observed when frozen porcine skin (but not fresh skin) was significantly more permeable to diclofenac-in-water than to the drug-in-microemulsion. In fact, the drug penetration from the microemulsion was not affected by the skin storage conditions, but it was increased when an aqueous solution was applied. However, this unusual phenomenon observed in non-freshly used porcine skin places a question mark on its relevancy for in vitro penetration studies involving aqueous vehicle systems.     

Coumarins ameliorate diabetogenic action of dexamethasone via Akt activation and AMPK signaling in skeletal muscle

Glucocorticoids are widely prescribed for lots of pathological conditions, however, can produce ‘Cushingoid’ side effects including central obesity, glucose intolerance, insulin resistance and so forth. Our study is intended to investigate the improving effects of coumarins on diabetogenic action of dexamethasone in vivo and in vitro and elucidate potential mechanisms. ICR mice treated with dexamethasone for 21 days exhibited decreased body weight, increased blood glucose and impaired glucose tolerance, which were prevented by fraxetin (40 mg/kg/day), esculin (40 mg/kg/day) and osthole (20 mg/kg/day), respectively. Esculin, fraxetin and osthole also could promote glucose uptake in normal C2C12 myotubes, and improve insulin resistance in myotubes induced by dexamethasone. Western blotting results indicated that esculin, fraxetin and osthole could boost Akt activation, stimulate GLUT4 translocation, thus alleviate insulin resistance. Esculin and osthole also could activate AMPK, thereby phosphorylate TBC1D1 at Ser237, and consequently ameliorate diabetogenic action of dexamethasone. Our study indicates coumarins as potential anti-diabetic candidates or leading compounds for drug development.     

Transdermal drug delivery of tricyclic antidepressants: effect of fatty acids

The aim of the present study was to investigate the effects of fatty acids on the permeation of tricyclic antidepressants, e.g., imipramine hydrochloride (IMH) and amitriptyline hydrochloride (AMH). Five percent w/v of saturated (lauric acid) and unsaturated (oleic acid, linoleic acid, linolenic acid, trans-elaidic acid and trans-vaccenic acid) fatty acids in an ethanol (EtOH):water (2:1) system were used in this study. Flux and lag-time of tricyclic antidepressants were significantly increased and reduced, respectively, compared with control (p < 0.05). There were no significant differences between the effects of lauric and unsaturated fatty acids, both cis and trans, on the permeation of IMH and AMH (except vaccenic acid in case of IMH). The formation of 'grain boundaries' by straight chain fatty acids (saturated and trans-unsaturated fatty acids) could not be observed by Fourier-transform infrared spectroscopy (FT-IR). However, perturbation or increased bilayer fluidity of Stratum corneum (SC) induced by cis-unsaturated fatty acid was observed by FT-IR.     

Metformin reduces airway inflammation and remodeling via activation of AMP-activated protein kinase

Recent reports have suggested that metformin has anti-inflammatory and anti-tissue remodeling properties. We investigated the potential effect of metformin on airway inflammation and remodeling in asthma. The effect of metformin treatment on airway inflammation and pivotal characteristics of airway remodeling were examined in a murine model of chronic asthma generated by repetitive challenges with ovalbumin and fungal-associated allergenic protease. To investigate the underlying mechanism of metformin, oxidative stress levels and AMP-activated protein kinase (AMPK) activation were assessed. To further elucidate the role of AMPK, we examined the effect of 5-aminoimidazole-4-carboxamide-1-β-4-ribofuranoside (AICAR) as a specific activator of AMPK and employed AMPKα1-deficient mice as an asthma model. The role of metformin and AMPK in tissue fibrosis was evaluated using a bleomycin-induced acute lung injury model and in vitro experiments with cultured fibroblasts. Metformin suppressed eosinophilic inflammation and significantly reduced peribronchial fibrosis, smooth muscle layer thickness, and mucin secretion. Enhanced AMPK activation and decreased oxidative stress in lungs was found in metformin-treated asthmatic mice. Similar results were observed in the AICAR-treated group. In addition, the enhanced airway inflammation and fibrosis in heterozygous AMPKα1-deficient mice were induced by both allergen and bleomycin challenges. Fibronectin and collagen expression was diminished by metformin through AMPKα1 activation in cultured fibroblasts. Therefore metformin reduced both airway inflammation and remodeling at least partially through the induction of AMPK activation and decreased oxidative stress. These data provide insight into the beneficial role of metformin as a novel therapeutic drug for chronic asthma.     

Transdermal delivery of methotrexate: past, present and future prospects

Mehotrexate has been reported as an immunosuppressant and an antimetabolite widely used in the treatment of rheumatoid arthritis and psoriasis. However, it causes various toxicities and has low bioavailability when taken orally, thus, it is desirable that the drug be delivered transdermally. The water solubility and charged structure of methotrexate, however, limits its use via the transdermal route mainly due to the highly organized microstructure of the stratum corneum. Hence, various technologies, such as chemical enhancers, iontophoresis, electroporation, ultrasound and microneedles, either alone or in combination, are being explored to enhance its permeability by disrupting the barrier property of the skin. The present article discusses the past, present and future of transdermal delivery of methotrexate.     

Prenylflavonoids from fruit of Macaranga tanarius promote glucose uptake via AMPK activation in L6 myotubes

Skeletal muscle is a major tissue of glucose consumption and plays an important role in glucose homeostasis. Prenylflavonoids, a component of Macaranga tanarius fruits, have been reported to have antioxidant, antibacterial, and anticancer effects. However, the effects of these compounds on skeletal muscle glucose metabolism are unclear. Here, we isolated five prenylflavonoids from M. tanarius fruits, and investigated the mechanism of action of these compounds on skeletal muscle cells using L6 myotubes. We found that isonymphaeol B and 3′-geranyl naringenin increased glucose uptake in a dose-dependent manner. Furthermore, both isonymphaeol B and 3′-geranyl naringenin increased AMPK phosphorylation but did not affect PI3K-Akt phosphorylation. Isonymphaeol B and 3′-geranyl naringenin also increased Glut1 mRNA expression and plasma membrane GLUT1 protein levels. These results suggest that isonymphaeol B and 3′-geranyl naringenin have beneficial effects on glucose metabolism through AMPK and GLUT1 pathway. Isonymphaeol B and 3′-geranyl naringenin may be potential lead candidates for antidiabetic drug development.

Graphical abstract