Permeation of piroxicam from the poloxamer gels

Formulation strategies to modulate drug release from poloxamer based in situ gelling systems

Introduction: Poloxamer based in situ gelling systems offer numerous advantages in drug delivery; however, their application as prolonged-release delivery platforms is limited mainly due to their weak mechanical properties and the interconnected aqueous network causing fast gel erosion and drug diffusion.Area covered: The focus of this review is to provide an insightful discussion on the formulation strategies that can be employed to sustain/prolong the drug release from poloxamer based in situ gelling systems. The review also outlines the formulation factors, influencing drug release from these systems.Expert opinion: The nature, composition, and concentration of poloxamers are the most critical factors in defining the rate of drug release from an in situ gelling matrix. Hydrophobic gel matrices have compact micellar arrangements resulting in slow diffusion and erosion. Depending on the intended clinical application, gel characteristics can be modulated, either by physical blending or by chemical crosslinking with additive materials, to slow release and improve residence time at the administration site. Incorporating drug-loaded particles into poloxamer gels sustains drug release by creating multiple rate-limiting release barriers. Chemical modification of poloxamers appears to be a promising strategy to obtain prolonged sustained release for parenteral application without compromising the rheological properties of the formulation.

Development of poloxamer gel formulations via hot-melt extrusion technology

Poloxamer gels are conventionally prepared by the "hot" or the "cold" process. But these techniques have some disadvantages such as high energy consumption, requires expensive equipment and often have scale up issues. Therefore, the objective of this work was to develop poloxamer gels by hot-melt extrusion technology. The model drug selected was ketoprofen. The formulations developed were 30% and 40% poloxamer gels. Of these formulations, the 30% poloxamer gels were selected as ideal gels. DSC and XRD studies showed an amorphous nature of the drug after extrusion. It was observed from the permeation studies that with increasing poloxamer concentration, a decrease in drug permeation was obtained. Other studies conducted for the formulations included in-vitro release studies, texture analysis, rheological studies and pH measurements. In conclusion, the hot-melt extrusion technology could be successfully employed to develop poloxamer gels by overcoming the drawbacks associated with the conventional techniques.

Design expert assisted formulation of topical bioadhesive gel of sertaconazole nitrate

PURPOSE

The objective of this work was to develop a bioadhesive topical gel of sertaconazole nitrate with the help of response-surface approach.

METHODS

Experiments were performed according to a 3-level factorial design to evaluate the effects of two independent variables [amount of Carbapol 934 = X1) and Sodium carboxymethylcellulose (NaCMC) = X2)] on the bioadhesive character of gel, rheological property of gel (consistency index), and in-vitro drug release. The best model was selected to fit the data.

RESULTS

Mathematical equation was generated by Design Expert® software for the model which assists in determining the effect of independent variables. Response surface plots were also generated by the software for analyzing effect of the independent variables on the response. The effect of formulation variables on the product characteristics can be easily predicted and precisely interpreted by using a 3-level factorial design and generated quadratic mathematical equations.

CONCLUSION

On the basis of product characteristics viscosity, bioadhesiveness, permeation study, in-vitro release, in-vivo studies, TPA and spreadability it can be concluded that the best batch of topical bioadhesive gel of Sertaconazole nitrate would be with 1% Carbopol 934 and 1% NaCMC.

Preparation, characterization, and in vitro permeation study of terbinafine HCl in poloxamer 407-based thermogelling formulation for topical application

Upon topical administration, a high penetration rate of antifungal drug into the infected site is desirable to reduce treatment length and systemic side effects which occur especially after a prolonged peroral administration. Thermogelling formulations composed of poloxamer 407, medium chain triglycerides, isopropyl alcohol, dimethyl isosorbide, and water for topical application were developed, and a lipophilic drug terbinafine HCl (TBF) was incorporated. Previously, a remarkable high permeation rate of a hydrophilic drug 5-aminolevulinic acid from this vehicle was evident compared to different creams from German Pharmacopoeia. By varying the composition of vehicle constituents, a broad range of consistencies and appearances was obtained. Up to 4% TBF could be solubilized in the vehicle. TBF fluxes at steady state across human stratum corneum from these formulations were higher than those from the German Pharmacopoeia Basiscreme Deutscher Arzneimittel Codex and a marketed product at similar concentration of 1%. TBF fluxes increased along with a higher content of TBF in the formulation. The amount of TBF retained in stratum corneum was higher compared to those from both standards of comparison (p < 0.01). The thermodynamic activity of TBF in the thermogelling formulation was lower compared to those in other formulations. Therefore, the nature of the vehicle and its interaction with TBF are suggested to play a significant role in explaining higher fluxes along with higher TBF content. Differential scanning calorimetry measurements revealed comparable T2 and T3 endothermic shifts from all examined formulations suggesting equal influences to the skin lipids.

In vitro properties of surface-modified solid lipid microspheres containing an antimalarial drug: halofantrine

OBJECTIVE

To formulate and evaluate in vitro, surface-modified solid lipid microspheres containing halofantrine using lipid matrix formed from goat fat and a phospholipid (P90H).

METHODS

The model drug, halofantrine in an increasing concentration of 1%, 2%, 3%, 4% and 5% w/w was incorporated into surface-modified solid lipid microspheres formulated by hot homogenization. Effect of drug concentration on the encapsulation efficiency was studied. The dispersion was evaluated using particle size, particle morphology, pH and encapsulation efficiency. The drug formulation with highest encapsulation efficiency was selected and used for the release studies and compared with the release from a commercial dosage form (Halfan® 250 mg tablet, Glaxo-Smithkline, Mayenne France) using simulated gastric fluid (SGF pH 1.2), simulated intestinal fluid (SIF pH 7.2) and phosphate buffer (pH 6.8) as biorelevant media. Results were analyzed statistically and the level of significance was taken to be P < 0.05).

RESULTS

Discrete and spherical solid lipid microspheres were produced. The particle size of the dispersion was low (32.48-33.87 μm) with minimal particle growth and high encapsulation efficiencies (86.8%-91.0%) after 3 months. The pH of the microspheres dispersion changed appreciably after 3 months. In vitro release result obtained revealed sustained and controlled drug release from the lipid microspheres compared with the tablet dosage form.

CONCLUSIONS

Formulation of halofantrine as solid lipid microspheres presents a better alternative to the conventional tablet formulation as the in vitro dissolution of the highly lipophilic halofantrine was highly improved.

Evaluation of glycofurol-based gel as a new vehicle for topical application of naproxen

In view of the good skin tolerability, glycofurol was used as a vehicle-based gel, and its effect in the topical penetration of Naproxen (NAP) was investigated. The aims of this study were to develop a suitable gel with bioadhesive property, spreadability, and viscosity for topical anti-inflammatory effect. Three gelling and adhesive agents were examined: Carbopol 974P, Gantrez AN 119, and polyvinylpyrollidone K30. Skin permeation rates and lag times of NAP were evaluated using the Franz-type diffusion cell in order to optimize the gel formulation. The permeation rate of NAP-based gel across the excised rat skin was investigated. A significant increase in permeability parameters such as steady-state flux (J(ss)), permeability coefficient (K(p)), and penetration index (PI) was observed in optimized formulation containing 2% Transcutol as an permeation enhancer. From skin irritation test, it was concluded that the optimized novel glycofurol-based gel formulation was safe to be used for topical drug delivery. The developed glycofurol-based gel appeared promising for dermal and transdermal delivery of naproxen and could be applicable with water-insoluble drugs, which would circumvent most of the problems associated with drug therapy.

Transdermal Transport of India Ink by Electromagnetic Electroporation in Guinea Pigs: An Ultrastructural Study

Transdermic administration by electroporation has developed over recent years for applying drugs in a variety of pathological processes. However, mechanisms are still not finally settled. India ink was applied to the backs of guinea pigs and for the transdermic transport short, high-voltage pulses (TDES, Dencort Dell) were administrated. Punch biopsies (4 mm) immediately taken after 24, 48, 72, 96 and at 26 days were studied by light and electronic microscopy. The ultrastructural characteristics and image pigment particles were reported. Particles of India ink were observed in the stratum corneum and in the epidermic keratinocytes of samples studied immediately after treatment. Particles were also seen in the epidermic and folicular keratinocytes, and in the papillary and reticular dermis (among collagen fibers, vessel walls, and macrophages) in all the subsequent biopsies; but not in the controls, which were conducted with electromagnetic waves alone. No tissue alterations were observed. The efficacy and noninvasive nature of electroporation for the transdermic administration of macromolecules is confirmed.

Preparation and evaluation of pranoprofen gel for percutaneous administration

The percutaneous delivery of nonsteroidal anti-inflammatory drug (NSAID) has the advantages of avoiding the hepatic first pass effect and delivering the drug to the inflammation site at a sustained, concentrated level over an extended period of time. Hydroxypropyl methylcellulose (HPMC) and poloxamer 407 were used in an attempt to develop new topical formulations of pranoprofen. The effects of the drug concentration (0.04, 0.08, 0.12, 0.16, and 0.20%) on the rate of drug release from HPMC-poloxamer 407 gels were examined using a synthetic cellulose membrane at 37+/-0.5 degrees C. The rate of drug permeation increased significantly with increasing drug concentration in the gels until the concentration reached 0.16%, and increased slightly thereafter. The effects of temperature on the rate of drug release from the 0.16% pranoprofen gels were evaluated at 32, 37, and 42 degrees C. The rate of drug release from the 0.16% pranoprofen gels increased with increasing temperature with activation energy (Ea) of 8.88 kcal/mol. Various penetration enhancers, such as nonionic surfactants and fatty acids, were incorporated in the gel formulation in an attempt to increase the level of drug permeation. Among the enhancers used, octanoic acid had the strongest enhancing effects with an enhancement factor of 3.09. The anti-inflammatory effect of the pranoprofen gel was evaluated using a rat paw-edema model. The 0.16% pranoprofen gel containing octanoic acid as an enhancer reduced the edema size by approximately 73% compared with that of the control group. These results highlight the feasibility of a topical gel formulation of pranoprofen containing an enhancer.

A review of poloxamer 407 pharmaceutical and pharmacological characteristics

Poloxamer 407 copolymer (ethylene oxide and propylene oxide blocks) shows thermoreversible properties, which is of the utmost interest in optimising drug formulation (fluid state at room temperature facilitating administration and gel state above sol-gel transition temperature at body temperature promoting prolonged release of pharmacological agents). Pharmaceutical evaluation consists in determining the rheological behaviour (flow curve or oscillatory studies), sol-gel transition temperature, in vitro drug release using either synthetic or physiological membrane and (bio)adhesion characteristics. Poloxamer 407 formulations led to enhanced solubilisation of poorly water-soluble drugs and prolonged release profile for many galenic applications (e.g., oral, rectal, topical, ophthalmic, nasal and injectable preparations) but did not clearly show any relevant advantages when used alone. Combination with other excipients like Poloxamer 188 or mucoadhesive polymers promotes Poloxamer 407 action by optimising sol-gel transition temperature or increasing bioadhesive properties. Inclusion of liposomes or micro(nano)particles in Poloxamer 407 formulations offers interesting prospects, as well. Besides these promising data, Poloxamer 407 has been held responsible for lipidic profile alteration and possible renal toxicity, which compromises its development for parenteral applications. In addition, new findings have demonstrated immuno-modulation and cytotoxicity-promoting properties of Poloxamer 407 revealing significant pharmacological interest and, hence, human trials are in progress to specify these potential applications.

Enhanced transdermal delivery of pranoprofen from the bioadhesive gels

Percutaneous delivery of NSAIDs has advantages of avoiding hepatic first pass effect and delivering the drug for extended period of time at a sustained, concentrated level at the inflammation site that mainly acts at the joint and the related regions. To develop the new topical formulations of pranoprofen that have suitable bioadhesion, the gel was formulated using hydroxypropyl methylcellulose (HPMC) and poloxamer 407. The effects of temperature on drug release was performed at 32 degrees C, 37 degrees C and 42 degrees C according to drug concentration of 0.04%, 0.08%, 0.12%, 0.16%, and 0.2% (w/w) using synthetic cellulose membrane at 37+/-0.5 degrees C. The increase of temperature showed the increased drug release. The activation energy (Ea), which were calculated from the slope of lop P versus 1000/T plots was 11.22 kcal/ mol for 0.04%, 10.79 kcal/mol for 0.08%, 10.41 kcal/mol for 0.12% and 8.88 kcal/mol for 0.16% loading dose from the pranoprofen gel. To increase the drug permeation, some kinds of penetration enhancers such as the ethylene glycols, the propylene glycols, the glycerides, the non-ionic surfactants and the fatty acids were incorporated in the gel formulation. Among the various enhancers used, propylene glycol mono laurate showed the highest enhancing effects with the enhancement factor of 2.74. The results of this study suggest that development of topical gel formulation of pranoprofen containing an enhancer is feasible.

Viscoelastic properties of Carbopol 940 gels and their relationships to piroxicam diffusion coefficients in gel bases

PURPOSE

This study was conducted to determine the effect of formula compositions on viscoelastic properties of piroxicam gels using Carbopol 940 as a gelling agent and to determine the relationships between viscoelastic properties of Carbopol 940 gel bases and diffusion coefficients of piroxicam in gel bases.

METHODS

Piroxicam gels (1.0% w/w) were prepared by using Carbopol 940 as a gelling agent and varying Carbopol 940 concentrations, glycerin, and sodium chloride contents. The in vitro release of piroxicam from gel bases to the receiving media, isotonic phosphate buffer solution (pH 7.4), were carried out using Franz-modified cell. The piroxicam diffusion coefficients were obtained by Higuchi's equation. Rheological property measurements of gel samples were performed via a cone and plate fluid rheometer. Relationships between viscoelastic properties of gel samples and piroxicam diffusion in gel bases were analyzed by Pearson's test at a p value of less than 0.05.

RESULTS

All piroxicam gels exhibited predominantly elastic solid behavior whose magnitude depended on Carbopol 940 concentration. Preparations containing good solvent exhibited more elastic solid characters. In contrast, the piroxicam gels containing higher sodium chloride contents possessed more viscous fluid behavior. Analyzed by Pearson's test at a p value of less than 0.05, piroxicam diffusion coefficients were directly proportional to loss tangent, but were inversely proportional to storage modulus, loss modulus, complex modulus, and viscosity.

CONCLUSIONS

There is a potential for predicting drug diffusion coefficients from their correlations to rheological parameters. This could be beneficial to the formulation design of transdermal drug delivery systems including mucoadhesive drug delivery systems.

Topical absorption of piroxicam from organogels—in vitro and in vivo correlations

In view of their good skin tolerability, glyceryl fatty acid esters were used as organogelators, and their effects in the topical penetration of piroxicam (Px) were investigated. The in vivo skin penetration was evaluated by measuring the anti-inflammatory effect in rats, where we found that Px incorporated into glyceryl fatty acid ester organogels exhibited a significantly greater inhibition of oedema than that of the placebo control either when applied locally (p < 0.001), or via transdermal absorption (p < 0.01 and < 0.05, respectively). As the Px concentration was increased, the extent of oedema inhibition rose in accordance with a power law. Comparisons with traditional galenic organogels and a marketed product revealed that the relative biological availability of Px was better from glyceryl fatty acid ester organogels, except when calculated for D1 versus T2 and T3. In order to predict the extent of in vivo skin absorption, we measured the penetration coefficient and the in vitro penetration. In accordance with theory, the extent of in vivo oedema inhibition increased as P(oct/w) increased, and maximum inhibition was observed at logP = 2.0211. However, the in vitro penetration through a synthetic membrane did not correlate with the in vivo results, the reason for which might be the different natures of the model barriers.

Development of lidocaine gels for enhanced local anesthetic action

In relieving local pains, lidocaine, one of ester type local anesthetics, has been used. To develop the lidocaine gels of enhanced local anesthetic effects, hydroxypropyl methylcellulose (HPMC) based bioadhesive polymer gel containing an enhancer was formulated. As the drug concentration in the gels increased up to 3%, the permeation rate of drug linearly increased, thereafter reaching a plateau. As the temperature of surrounding solutions increased, the permeation of drug increased. The activation energy of drug permeation was 3.29 kcal/mol for lidocaine. The permeation rate of drug through skin was studied using various enhancers, such as glycols, non-ionic surfactants, and bile salts. Among the enhancers studied, diethylene glycol showed the greatest enhancing effects on drug permeation through skin. The analgesic activity was examined using a tail-flick analgesimeter. In the area under the efficacy curve (AUEC) of the rat-tail flick tests, lidocaine gel containing diethylene glycol showed about 3.89-fold increase in analgesic activity compared with the control. The addition of vasoconstrictor in the gels prolonged the analgesic effects. The result of this study supports that the bioadhesive gel with efficient anesthetic effect could be developed using HPMC with combination of enhancer and vasoconstrictor.

Development of the Bioadhesive Tetracaine Gels for Enhanced Local Anesthetic Effects

To develop the new local anesthetic formulations with a suitable bioadhesive property, hydroxypropyl methylcellulose (HPMC)-based gel was formulated. As the drug concentration in the gels, and the temperature of surrounding solutions increased, the drug release increased. The activation energy of tetracaine permeation was 4.47 kcal/mol. The effects of permeation enhancers on the permeation rate of drug through skin were studied using various enhancers, such as the glycols, the nonionic surfactants, and the bile salts. Among the enhancers used, polyoxyethylene 2-oleyl ether showed the highest enhancing effects on drug permeation through skin. The analgesic activity was examined using a tail-flick analgesimeter. In the AUEC (area under the efficacy curve) of the rat-tail flick test, tetracaine gel containing polyoxyethylene 2-oleyl ether showed about 3.2-fold increase in analgesic activity compared with the control. The results of this study support that the tetracaine gels with efficient anesthetic effects could be developed using HPMC and poloxamer with combination of enhancer and vasoconstrictor.

Transbuccal permeation, anti-inflammatory activity and clinical efficacy of piroxicam formulated in different gels

In attempts to avoid the systemic side effects of piroxicam (PC) (e.g. gastrotoxicity), several buccal gel formulations containing PC were prepared and their effects on the characteristics of the drug permeation through rabbit buccal mucosa in-vitro were evaluated using a Franz-type diffusion cell. The general rank order of the total flux of 0.5% PC from gels was found to be: hydroxypropylmethylcellulose (HPMC, 2.5%) > hydroxypropylcellulose (HPC, 2.5%) >or= sodium alginate (Na alg., 7%) > methylcellulose (MC, 3%) > hydroxyethylcellulose (HEC, 1.5%) > carbopol 934 (Carb. 934, 1%) >or= sodium carboxymethylcellulose (NaCMC, 2%) > pluronic F-127 (PF-127, 20%) > polyvinyl alcohol (PVA, 10%). The effect of various penetration enhancers 1% sodium lauryl sulphate (NaLS), 3% sodium deoxycholate (NaDC), 3% sodium tauroglycocholate (NaTGC) on the rate of permeation across the excised buccal mucosa (of 0.5% PC in gels prepared using 3% MC, 2.5% HPMC or 7% Na alg. base) and histology of the buccal epithelium was also investigated. Pharmacodynamic evaluation of the anti-inflammatory activity of PC in these gel formulations (containing 3% NaDC as an enhancer) was carried out using the kaolin-induced rat paw oedema method. The results obtained indicated that PC administered in 7% Na alg. or 2.5% HPMC gel bases was significantly more effective than the 3% MC gel and oral drug solution in suppressing oedema formation in rats. Comparative clinical studies were conducted in patients with post-operative dental pain and oedema following maxillofacial operations. The results revealed that 7% Na alg. and 2.5% HPMC gel formulations applied to the buccal mucosa were slightly better than or equally effective to the orally administered commercial product (Feldene Flash) tablet) in reducing pain level, swelling and tenderness within a period of 4 days. These findings suggest that PC (0.5%) administered in the buccal gel may present a potential therapeutical use as a strong anti-inflammatory and analgesic agent.

Percutaneous absorption of non-steroidal anti-inflammatory drugs from in situ gelling xyloglucan formulations in rats

The potential of gels formed in situ by dilute aqueous solutions of a xyloglucan polysaccharide derived from tamarind seed as sustained release vehicles for percutaneous administration of non-steroidal anti-inflammatory drugs has been assessed by in vitro and in vivo studies. Chilled aqueous solutions of xyloglucan that had been partially degraded by beta-galactosidase formed gels at concentrations of 1-2% w/w when warmed to 37 degrees C. The in vitro release of ibuprofen and ketoprofen at pH 7.4 from the enzyme degraded xyloglucan gels and the subsequent permeation of these fully ionized drugs through cellulose membranes followed root-time kinetics over a period of 12 h after an initial lag period. Diffusion coefficients were appreciably higher when the drugs were released from 1.5% w/w xyloglucan gels than when released from 25% w/w Pluronic F127 gels formed in situ under identical conditions. The difference in release rates was attributed to differences in the structure of the gels. The permeation rate of ibuprofen through excised skin was higher than that of ketoprofen when released from both gels, but of similar magnitude through cellulose membranes. Plasma concentrations of ibuprofen and ketoprofen from gels formed in situ following topical application of chilled aqueous solutions of xyloglucan and Pluronic F127 to the abdominal skin of rats were compared. The bioavailabilities of ibuprofen and ketoprofen were significantly higher when released from xyloglucan gels compared to Pluronic F127 gels. Occlusive dressing techniques had a greater enhancing effect on the bioavailability of ibuprofen when released from Pluronic gels.

Controlled release of triprolidine using ethylene-vinyl acetate membrane and matrix systems

The studies on the permeability of triprolidine through ethylene-vinyl acetate (EVA) copolymer membrane using two-chamber diffusion cell was carried out to develop the controlled delivery system. To evaluate the effect of drug concentration in reservoir, polyethylene glycol (PEG) 400 was added to saline solution as a solubilizer and a sink condition was maintained in the receptor solution. The permeation rate of drug through EVA membrane was proportional to PEG 400 volume fraction. A linear relationship existed between the permeation rate and the reciprocal of the membrane thickness. Triprolidine-containing matrix was fabricated with EVA copolymer to control the release of the drug. The plasticizers was added for preparing the pore structure of EVA membranes to increase the drug release. The effects of PEG 400, vinyl acetate (VA) contents of EVA, membrane thickness, drug concentration, temperature, and plasticizers, on drug release were studied. The release rate of drug from the EVA matrix increased with PEG 400 volume fraction, increased temperature and drug loading doses. An increased vinyl acetate comonomer content in EVA membrane increased the drug release rate and permeability coefficient. Among the plasticizers used such as alkyl citrates and phthalates, tetra ethyl citrate showed the best enhancing effects showing the enhancement factor of 1.88. The release of triprolidine from the EVA matrix follows a diffusion controlled model, where the quantity released per unit area is proportional to the square root of time. The controlled release of triprolidine could be achieved using the EVA polymer including the plasticizer.

In vitro topical application and in vivo pharmacodynamic evaluation of nonivamide hydrogels using Wistar rat as an animal model

Nonivamide, a so-called synthetic capsaicin, is a substitute for capsaicin which has a similar chemical structure and pharmacological activities as those of capsaicin. The purposes of this study were to explore the in vivo pharmacodynamic responses of nonivamide in hydrogels using Wistar rat as an animal model and to correlate the in vivo results with in vitro topical application. The incorporation of Pluronic F-127 polymer into hydrogels resulted in retarded release of nonivamide. Chitosan and carboxymethylcellulose hydrogels produced higher levels of in vitro nonivamide permeation and skin distribution. The in vivo effects of nonivamide on skin perturbation and vasodilation were found to differ depending on dose and duration after topical application. Quantification of transepidermal water loss was demonstrated to correlate with the measured in vitro skin distribution of nonivamide. The various doses of nonivamide in the hydrogels did not markedly influence erythematous reactions of skin as determined by colorimetric measurements. Hydrogel formulations of nonivamide delivered more drug to the skin and produced greater pharmacodynamic activities than did cream bases of capsaicin.

Application of TPX polymer membranes for the controlled release of triprolidine

Oral administration of triprolidine, antihistamines, may cause many adverse effects such as dry mouth, sedation, dizziness and transdermal drug delivery was considered. Poly(4-methyl-1-pentene) (TPX) membrane, which has good mechanical strength was fabricated by the casting method. TPX membranes was a little brittle and the plasticizers was added for preparing the membranes. The present study was carried out to evaluate the possibility of using the polymer TPX membrane as a controlling membrane and further develop a TPX matrix system for transdermal delivery of triprolidine. The effects of molecular weights of TPX, plasticizers, polyethylene glycol (PEG) 400, drug concentration, and temperature on drug release were studied. The solubility of triprolidine increased exponentially as the increased volume fraction of PEG 400 in saline, and the rate of permeation through TPX membrane was proportional to PEG 400 volume fraction. The release rate of drug from the TPX matrix increased with increased temperature and drug concentration. Among the plasticizers used such as alkyl citrates, phthalates and sebacate, tetra ethyl citrate (TEC) showed the best enhancing effects. Enhancement factor of TEC was 3.76 from TPX matrix at 37 degrees C. The transdermal controlled release of triprolidine system could be developed using the TPX polymer including the plasticizer.

Sensitive LC determination of piroxicam after in vitro transdermal permeation studies

A direct, very sensitive, simple and rapid high-performance liquid chromatographic (HPLC) method for the determination of piroxicam, with tenoxicam as internal standard, has been developed and validated. Samples were chromatographed on a 5 microm Scharlau C(18) column. The mobile phase was a mixture of acetonitrile-acetic acid 4% (pH 2.8) (45:55, v/v). Detection was at 354 nm and the run time was 7 min. The limit of detection was 0.025 microg/ml. The detector response was found to be linear in the concentration range 0.05-9 microg/ml. This HPLC assay has been applied to measure the 'in vitro' percutaneous permeation of piroxicam through abdominal hairless rat skin, using Franz-type diffusion cells, in order to obtain the concentration-time profiles of piroxicam.

Topical permeation characteristics of diclofenac sodium from NaCMC gels in comparison with conventional gel formulations

Topical gel formulations of diclofenac sodium were prepared by using sodium carboxymethylcellulose (NaCMC), a low-toxicity cellulose polymer as a gel-forming material that is biocompatible and biodegradable. The influence of various formulation variables, such as initial drug concentrations and NaCMC concentration, and certain skin permeation enhancers on release characteristics of the diclofenac sodium from the prepared gels through a standard cellophane membrane was studied in comparison with four commercially available gel formulations of diclofenac sodium,. The cumulative amounts released and the apparent release rates were higher for the prepared gels in comparison with the commercial formulations. Skin permeation studies using abdominal rat skin revealed good improvement of skin permeation characteristics of diclofenac sodium using NaCMC gels as compared to the commercial gels. The cumulative amount permeated at 6 h (microg/cm2), steady-state flux Jss (microg/cm2 h), lag time tL (h), permeability coefficient kp (cm/s), partition coefficient k, and diffusion coefficient D (cm2/s) were determined for the prepared gels in comparison with the commercial gels. Skin permeation enhancers such as isopropyl alcohol (IPA), Tween 80, and alpha-tocopherol polyethylene glycol succinate (TPGS) exhibited little or no effect on the permeation characteristics of diclofenac sodium. Infrared (IR) spectrum and differential scanning calorimetry (DSC) studies on the pure diclofenac sodium, NaCMC, and their physical mixture at a 1:1 ratio revealed that there was no positive evidence for the interactions between the drug and NaCMC, indicating the compatibility of the drug and the vehicle. Based on experimental results, preparation of diclofenac sodium gels using NaCMC vehicle is promising.

In vitro and in vivo evaluations of topically applied capsaicin and nonivamide from hydrogels

The purpose of this study was designed to investigate the in vitro and in vivo skin absorption of capsaicin and nonivamide from hydrogels. Various commercialized creams of capsaicin were also compared with hydrogels. Both skin stripping technique and Mexameter were applied to evaluate the level of capsaicin and nonivamide retained in stratum corneum (SC) and skin erythema in vivo. The partition of drug between skin and the hydrogel matrix was considered to play an important role in the permeation process. The in vitro permeation of capsaicin from hydrogels depends on the physicochemical nature and the concentration of the polymer used. The incorporation of nonionic Pluronic F-127 polymer into hydrogels resulted in a retarded release of capsaicin. On the other hand, the in vitro capsaicin permeation showed higher levels in cationic chitosan and anionic carboxymethyl cellulose (CMC) hydrogels than cream bases. The permeation of nonivamide was retarded at the late stage of in vitro application. The inter-subject variation was more significant in the in vivo study than in vitro skin permeation experiments. The cream induced in vivo skin erythema depending on the drug concentration, however, the dose-dependence was not observed in hydrogels. Nonivamide-treated skin showed stronger erythema than capsaicin-treated skin. The present study indicates that there is a moderate correlation between in vitro skin permeation and in vivo erythema responses of topically applied capsaicin and nonivamide. The correlation between drug amount in SC and skin erythema test in vivo was also observed.

Influence of piroxicam: hydroxypropyl-beta-cyclodextrin complexation on the in vitro permeation and skin retention of piroxicam

The interactions between piroxicam (Px) and hydroxypropyl-beta-cyclodextrin (HPbetaCD) were thoroughly investigated both in solution and the solid state. The solubility studies have demonstrated the formation of a Px:HPbetaCD inclusion complex with 1:1 stoichiometry. The addition of propylene glycol to the medium produced less stable complexes, revealing the fact of this co-solvent probably acting as a competing agent. Equimolecular Px:HPbetaCD solid systems were prepared using the co-precipitation method and then fully characterized by X-ray diffractometry, infrared spectra and differential scanning calorimetry. A topical gel formulation containing Px, as inclusion complex with HPbetaCD, was developed in order to study the influence of Px complexation on its release rate and skin percutaneous permeation. The formation of Px:HPbetaCD complexes did not increase either Px release from the vehicle or its skin permeation. However, Px complexation with HPbetaCD allowed the incorporation of a higher quantity of Px into the gel, which resulted in a considerable increase in the Px released and permeated. Skin pretreatment with different HPbetaCD solutions, followed by the application of control gel, showed no enhancing capacity. The amount of Px retained in the skin, after pretreatment experiments, was found to be very similar to that obtained without skin pretreatment and was observed to be related to flux values through the skin.

Improvement of gene transfer to cervical cancer cell lines using non-viral agents

Virus-like particles (VLPs) composed of recombinant capsid protein L1 and L2 of human papillomavirus type 16 were conjugated with polylysine (PL) and gene transfer was performed using VLP-PL conjugates to allow the expression of targeted gene. When HeLa cells were incubated with VLP-PL conjugate coupled with plasmid cytomegalovirus beta-galactosidase (pCMVbeta-gal), about 10% of cells were transfected and demonstrated beta-galactosidase activity. Hence chloramphenicol acetyltransferase activity was also expressed significantly in VLP-PL-plasmid simian virus 2 chloramphenicol acetyl transferase (pSV2CAT)-transfected cells, VLP-PL conjugate was tested whether it could transfer a tumor suppressor gene, pCMVp53, to HeLa cells and the exogenously provided p53 gene complexed to VLP-PL conjugate was detected from HeLa cells by polymerase chain reaction (PCR) analysis. Interestingly, additional increase of transfection efficiency was demonstrated in the presence of poloxamer 407 when C-33A cells were transfected with VLP-PL-pCMVbeta-gal complex. The result support the notion that VLP-PL conjugate may be a promising vector to transfer genetic materials into cancer cells and poloxamer 407 can be used for enhancing the transfection efficiency of VLP-PL conjugate.

Enhanced efficacy by percutaneous absorption of piroxicam from the poloxamer gel in rats

The pharmacokinetics and anti-inflammatory activity of piroxicam from the poloxamer 407 gel were determined to investigate percutaneous absorption of piroxicam from poloxamer gels in rats. The poloxamer 407 gel containing 1% piroxicam showed significant inhibition of carragenin-induced rat foot swelling when compared to the control group. The extent of inhibition of swelling (%) showed a linear relationship with the logarithm of piroxicam dose within approximately 0.4-3.2 mg/kg. The enhancing effect of polyoxyethylene-2-oleyl ether, non-ionic surfactant on the percutaneous absorption of piroxicam from poloxamer 407 gel was evaluated in rats. The piroxicam gel containing polyoxyethylene-2-oleyl ether increaesd the relative bioavailability approximately 1.8-fold compared with the gel without enhancer. Percutaneous administration of piroxicam gel containing polyoxyethylene-2-oleyl ether to rats showed a relatively constant, sustained blood concentration with minimal fluctuation.