Sun Woo Jang

Mechanical properties and in vivo healing evaluation of a novel Centella asiatica-loaded hydrocolloid wound dressing.

To develop a novel sodium alginate based Centella asiatica (CA)-loaded hydrocolloid wound dressing (HCD) providing excellent mechanical properties and improved wound healing, numerous CA-loaded HCDs were prepared with various ingredients using the hot melting method. The effect of sodium alginate, styrene-isoprene-styrene copolymer (SIS) and petroleum hydrocarbon resin (PHR) on the mechanical properties of CA-loaded HCDs was investigated. The effect of disintegrants on swelling and drug release was assessed. Moreover, the in vivo wound healing potentials of the selected CA-loaded HCD in various wound models such as abrasion, excision and infection were evaluated in comparison with the commercial product. Polyisobutylene and SIS hardly affected the mechanical properties, but PHR improved the tensile strength and elongation at break. Disintegrants such as croscarmellose sodium, sodium starch glycolate and crospovidone improved the swelling ratio of the CA-loaded HCD. Furthermore, the CA-loaded HCD without croscarmellose sodium poorly released the drug, but that with 2% croscarmellose sodium showed about 27% drug release in 24h. In particular, the CA-loaded HCD composed of CA/polyisobutylene/SIS/PHR/liquid paraffin/sodium alginate/croscarmellose sodium at the weight ratio of 1/8/25/25/12/27/2 furnished excellent mechanical properties and drug release. As compared with the commercial product, it offered improved healing effects in excision, infection and abrasion type wounds in rats. Thus, this novel CA-loaded HCD could be a potential candidate for the treatment of various wounds.

Improved oral absorption and chemical stability of everolimus via preparation of solid dispersion using solvent wetting technique

The aim of this study was to improve the physicochemical properties and oral absorption of poorly water-soluble everolimus via preparation of a solid dispersion (SD) system using a solvent wetting (SW) technique. The physicochemical properties, drug release profile, and bioavailability of SD prepared by SW process were also compared to SD prepared by the conventional co-precipitation method. Solid state characterizations using scanning electron microscopy, particle size analysis and X-ray powder diffraction indicated that drug homogeneously dispersed and existed in an amorphous state within the intact polymeric carrier. Whereas, a film-like mass was obtained by a co-precipitation method and further pulverization step was needed for tabletization. The drug release from the SD tablet prepared by SW process at a ratio of drug to hydroxypropyl methylcellulose of 1:15 was markedly higher than the drug alone and equivalent to the marketed product (Afinitor(®), Novartis Pharmaceuticals), a SD tablet prepared by co-precipitation method, archiving over 75% the drug release after 30 min. At the accelerated (40°C/75% R.H.) and stress (80°C) stability tests, the novel formula was more stable than drug powder and provided comparable drug stability with the commercially available product, which contains a potentially risky antioxidant, butylated hydroxyl toluene. The pharmacokinetic parameters after single oral administration in beagles showed no significant difference (P>0.01) between the novel SD-based tablet and the marketed product. The results of this study, therefore, suggest that the novel SD system prepared by the solvent wetting process may be a promising approach for improving the physicochemical stability and oral absorption of the sirolimus derivatives.

In Vivo Wound‐Healing Effects of Novel Benzalkonium Chloride‐Loaded Hydrocolloid Wound Dressing

Preclinical Research

Comparison of Piroxicam Pharmacokinetics and Anti-Inflammatory Effect in Rats after Intra-Articular and Intramuscular Administration

This study evaluated the pharmacokinetic profile and therapeutic efficacy of piroxicam (PX), a long acting non-steroidal anti-inflammatory drug for the treatment of arthritis, following intra-articular (IA) injection in comparison to the pharmacokinetic profile and therapeutic efficacy of PX after intramuscular (IM) injection. In the pharmacokinetic study in rats, systemic exposure and pharmacokinetic parameters of PX after a single IA dose were compared with systemic exposure and pharmacokinetic parameters of PX after administration of the same dose IM (0.6 mg/kg). The anti-inflammatory and analgesic effects of IA PX were evaluated simultaneously in a monoiodoacetate-induced osteoarthritis rat model. The plasma PX concentration rapidly rose following IA injection, and it was comparable to the plasma PX concentration following IM injection, suggesting the rapid efflux of the drug molecule from the joint cavity. However, in the efficacy study, the IA PX administration significantly reduced the knee swelling by reducing the level of prostaglandin E2 in the joint, compared to that following administration of IA vehicle and after administration of the IM PX dose. In addition, we found that the anti-inflammatory and anti-nociceptive efficacies of IA PX were synergistically increased upon co-treatment with hyaluronic acid (HA), a potent agent for the treatment of osteoarthritis, at the weight ratio of 1:1 or 1:2, and these effects were more pronounced than those following administration of HA or PX alone. In conclusion, this study demonstrated the efficacy of the IA use of PX alone and/or in combination with HA in osteoarthritis.

Design of pH-responsive alginate raft formulation of risedronate for reduced esophageal irritation

Risedronate sodium (RA), a pyridinyl bisphosphonate, is widely used in the treatment of osteoporosis. However, the free acid form of the bisphosphonate below pH 3.5 has the potential to produce severe impatience of the upper gastrointestinal tract, particularly esophagitis. A pH-responsive raft-forming tablet (PRR-T) was designed to prevent the esophageal irritation, mainly consisting of low-molecular-weight alginate (LFR 5/60, 300 mg) as raft-forming polymer, sodium bicarbonate (1000 mg) as gas-generating agent and citrate and sodium citrate (600 and 200 mg, respectively) as buffer system. A PRR-T was rapidly liquefied in water within 80 s with a low viscosity 8.0 mPa s, offering ease of swallowing in patients. A formulation profoundly neutralized simulated gastric fluid over pH 5.5, leading to an ionization of the bisphosphonate, without raft formation. On the other hand, the raft was rapidly formed on the top layer preventing the reflux of RA, if the contact with acidic medium is much higher than 0.5 N of hydrochloric acid. Nevertheless, the release rate of the drug was equivalent, providing over 95% release within 5 min. Our study demonstrated the potential usefulness of alginate-based PRR-T for an oral therapy with bisphosphonates for reduced esophageal adverse experiences.

Reduced Food-Effect on Intestinal Absorption of Dronedarone by Self-microemulsifying Drug Delivery System (SMEDDS)

The oral absorption of dronedarone (DRN), a benzofuran derivative with anti-arrhythmic activity, is significantly affected by food intake. The absolute bioavailability of the marketed product (Multaq, Sanofi, U.S.) was about 4% without food, but increased to 15% when administered with a high fat meal. Therefore, to reduce the food-effect on the intestinal absorption of DRN, a novel self-microemulsifying drug delivery system (SMEDDS) was formulated and the comparative in vivo absorption studies with the marketed product were carried out using male beagle dogs either in the fasted or fed state. The SMEDDS consisted of the drug, Labrafil M 1944CS, and Kolliphor EL in a weight ratio of 1 : 1 : 2, rapidly formed a fine oil-in-water emulsion with a droplet size less than 50 nm. An in vivo absorption study revealed that the area-under-curve (AUC0-24 h) and maximal plasma concentration (Cmax) were 10.4-fold (p<0.05) and 8.6-fold (p<0.05) higher, respectively, after the marketed product was orally administered to beagles in the fed state when compared to those in the fasted state. This food-effect were remarkably alleviated by SMEDDS formulation, with AUC0-24 h and Cmax 2.9-fold (p<0.05) and 2.6-fold (p<0.05) higher in the fed state when compared to the fasted state, by facilitating intestinal absorption of DRN in the fasted state. The results of this study suggest that SMEDDS may decrease the differences in oral absorption of DRN between the prandial states, improving therapeutic efficacy as well as patient compliance.

In vivo gastric residence and gastroprotective effect of floating gastroretentive tablet of DA-9601, an extract of Artemisia asiatica, in beagle dogs.

Objective DA-9601, an extract of Artemisia asiatica containing eupatilin and jaceosidin as active compounds, has been prescribed to treat gastritis in Asia. In recent times, sustained-release, floating gastroretentive (GR) tablets of DA-9601 are available on the market. In the present study, the physical properties and in vitro drug release profile, in vivo gastric residence time, and gastroprotective effect of GR tablet were compared to those of immediate release (IR) tablets of DA-9601. Method In vitro buoyancy behavior (floating lag time and duration) and release profile of eupatilin were assessed in acidic medium. The in vivo intragastric behaviors of the barium sulfate-loaded IR and GR tablets were evaluated in beagle dogs by radiographic studies. Local gastroprotective effect was compared in an experimentally induced gastric lesion in beagle dogs after oral administration of IR (three times per day) or GR (twice daily) tablets for 15 days. Results Upon contact with gastric juice, a low-density floating tablet (apparent density of 0.93 g/cm3) was buoyant on the medium and was upheld for 14 hours, providing sustained drug release profile, whereas the IR tablet disintegrated within 10 minutes, showing complete drug release within 2 hours. In vivo radiographic studies showed that the GR tablet was retained for >4 hours in the stomach. Both DA-9601 formulations remarkably alleviated gastric mucosal injury compared to placebo group, when observed by gastric endoscopy. Conclusion Twice-daily GR tablets exhibited a prolonged gastric residence time and a remarkable mucosal restoration effect in animal models. Therefore, the GR system of DA-9601 could be a substitute dosage form for the treatment of gastritis, while reducing the dosing frequency and thus improving patient compliance.

Preparation of Solid Dispersion of Dronedarone Hydrochloride with Soluplus® by Hot Melt Extrusion Technique for Enhanced Drug Release

In order to enhance the dissolution rate of dronedarone hydrochloride (DRN), a novel Soluplus(®) (polyethyleneglycol-polyvinyl caprolactam-polyvinyl acetate grafted copolymer)-based solid dispersion (SD) was formulated using a hot melt extrusion technique. The physical characteristics determined using scanning electron microscopy and X-ray powder diffraction, revealed that the active compound was molecularly dispersed in the amphiphilic polymer in a stable amorphous form. The dissolution rate of DRN from the tablet dosage form of SD extrudate consisted of the drug and Soluplus(®) in a weight ratio of 1 : 1, and was obviously more rapid and higher than that of the intact drug and marketed product (Multaq(®), Sanofi, U.S.A.) at pH 1.2, 4.0 and 6.8. This suggests that Soluplus(®)-based SD formula can be a promising approach for enhancing the dissolution and oral absorption of DRN with a simple preparation process.

Microsuspension of fatty acid esters of entecavir for parenteral sustained delivery

&NA; Entecavir (EV), an anti‐viral agent for hepatitis B infection, should be administered under fasted state, as intestinal absorption of this hydrophilic compound is markedly decreased under post‐prandial conditions. Herein, in order to improve therapeutic adherence, a parenteral sustained delivery system was constructed, by synthesizing water‐insoluble ester prodrugs of the nucleotide analogous with fatty acids. EV‐3‐palmitate (named EV‐P), exhibited the lowest solubility in phosphate buffered saline (pH 7.4, 1.1 &mgr;g/ml), with extended release profile compared with EV, EV‐3‐myristate, and EV‐3‐stearate, was selected as a candidate to formulate drug suspension. The crystalline suspension was fabricated using anti‐solvent crystallization technique, with a mean particle size of 7.7 &mgr;m. After subcutaneous (SC) injection in beagle dogs (0.43 mg/kg as EV), the plasma concentrations of EV were markedly protracted with lowered maximum plasma concentration (Cmax, 4.7 ng/ml), extended time required to reach Cmax (Tmax, 9.0 days), and lengthened elimination half‐life (T1/2, 129.3 h) compared with those after oral administration (0.0154 mg/kg, Cmax, 15.4 ng/ml; Tmax, 0.01 days; T1/2, 4.1 h). The systemic exposure of the lipidic prodrug was below 0.1% compared with that of EV following SC injection, denoting that EV‐P was rapidly converted into the parent compound in blood. Therefore, SC delivery of EV‐P microsuspension can be an alternative to oral EV therapy, offering prolonged pharmacokinetic profile after single injection. Graphical abstract Figure. No caption available.

Design and in vivo evaluation of entecavir-3-palmitate microcrystals for subcutaneous sustained delivery

ABSTRACT The objectives of this study were to formulate microcrystals of entecavir‐3‐palmiate (EV‐P), a palmitic acid ester of entecavir (EV), and evaluate the influence of particle size on its pharmacokinetic behavior following subcutaneous (SC) injection. Systemic toxicity and local tolerability of the hepatitis B anti‐viral suspension were further evaluated in normal rats. EV‐P microcrystals possessing median diameters of 2.1, 6.3, and 12.7&mgr;m were fabricated using anti‐solvent crystallization technique with polysorbate 20 and polyethylene glycol 4000 as steric stabilizer. Dissolution rate of EV‐P microcrystals was controlled by adjusting the particle size, under sink condition. Pharmacokinetic profiles of 2.1&mgr;m‐sized and 6.3&mgr;m‐sized EV‐P microcrystals were quite comparable (1.44mg/kg as EV), over 46days in rats. The absorption rate and extent of EV after SC injection of 12.7&mgr;m‐sized microcrystals were significantly retarded, due to its slower dissolution rate in aqueous media. No single‐dose systemic toxicity was observed after SC injection of high dose of EV‐P microcrystal suspension (30–300mg/kg as EV). The microcrystals were tolerable in the injected site, showing mild inflammatory responses at a dose of 30mg/kg. Therefore, the novel microcrystal system with median particle size of below 6.3&mgr;m is expected to be a unique long‐acting system of the anti‐viral agent, improving patient’s compliance with chronic disease.