Effect of formulation variables on the percutaneous permeation of ketoprofen from gel formulations

Effects of formulation variables on the in vitro performance of testosterone transdermal gel

The variation in the critical formulation variables during life-cycle of the drug product may result in undesirable changes in product performance. The current study aimed at evaluating the effects of formulation variables on the in vitro performance of carbopol-loaded testosterone gel. The formulation variables included concentrations of permeation enhancers, testosterone, ethanol, carbopol and sodium hydroxide. In vitro evaluation of the product performance included assessment of the rheological and morphological properties, kinetics of ethanol evaporation, and drug permeation through human cadaver skin. The results revealed that carbopol, sodium hydroxide and testosterone concentrations increased the viscosity of the gels significantly (p < 0.05). However, carbopol concentration was the only critical variable to affect the yield stress of the gel. The concentration of ethanol was critical to metamorphosis of the gel due to solvent evaporation upon application to skin with minor contributions from other formulation variables. The increase in concentration of isopropyl myristate or isopropyl palmitate to 5%, ethanol to 70%, and testosterone to 2%, enhanced the testosterone permeation across the skin by ten-folds. Synergistic effects of ethanol and permeation enhancers on testosterone permeation was observed. In conclusion, strict control over the critical formulation variables should be exercised during manufacturing to ensure desired product performance.

Skin-on-a-Chip Device for Ex Vivo Monitoring of Transdermal Delivery of Drugs-Design, Fabrication, and Testing

To develop proper drug formulations and to optimize the delivery of their active ingredients through the dermal barrier, the Franz diffusion cell system is the most widely used in vitro/ex vivo technique. However, different providers and manufacturers make various types of this equipment (horizontal, vertical, static, flow-through, smaller and larger chambers, etc.) with high variability and not fully comparable and consistent data. Furthermore, a high amount of test drug formulations and large size of diffusion skin surface and membranes are important requirements for the application of these methods. The aim of our study was to develop a novel Microfluidic Diffusion Chamber device and compare it with the traditional techniques. Here the design, fabrication, and a pilot testing of a microfluidic skin-on-a chip device are described. Based on this chip, further developments can also be implemented for industrial purposes to assist the characterization and optimization of drug formulations, dermal pharmacokinetics, and pharmacodynamic studies. The advantages of our device, beside the low costs, are the small drug and skin consumption, low sample volumes, dynamic arrangement with continuous flow mimicking the dermal circulation, as well as rapid and reproducible results.

Cross-Linked Hydrogel for Pharmaceutical Applications: A Review

Hydrogels are promising biomaterials because of their important qualities such as biocompatibility, biodegradability, hydrophilicity and non-toxicity. These qualities make hydrogels suitable for application in medical and pharmaceutical field. Recently, a tremendous growth of hydrogel application is seen, especially as gel and patch form, in transdermal drug delivery. This review mainly focuses on the types of hydrogels based on cross-linking and; secondly to describe the possible synthesis methods to design hydrogels for different pharmaceutical applications. The synthesis and chemistry of these hydrogels are discussed using specific pharmaceutical examples. The structure and water content in a typical hydrogel have also been discussed.

Effect of phonophoresis on skin permeation of commercial anti-inflammatory gels: sodium diclofenac and ketoprofen

This study evaluated the use of ultrasound in combination with the commercial anti-inflammatory drugs ketoprofen and sodium diclofenac, according to the parameters used in physiotherapy. Ketoprofen and sodium diclofenac were used in the Franz diffusion cell model adapted to an ultrasound transducer in three conditions: no ultrasound, one application of ultrasound and two applications of ultrasound. High-performance liquid chromatography was used to quantify the total amount of drug permeating skin per unit area, as well as flux and latency. The results showed that for ketoprofen, the amount of drug permeating skin and flux increased with two ultrasound applications. Permeation of sodium diclofenac decreased in the presence of ultrasound. Ultrasound parameters and drug properties must be considered in the use of phonophoresis.

Formulations for trans-tympanic antibiotic delivery

We have developed a drug delivery system for prolonged trans-tympanic antibiotic delivery from a single dose administration. Increased permeability to ciprofloxacin of the intact tympanic membrane (TM) was achieved by chemical permeation enhancers (CPEs--bupivacaine, limonene, sodium dodecyl sulfate); this was also seen by CPEs contained within a hydrogel (poloxamer 407) to maintain the formulation at the TM. The CPE-hydrogel formulation had minimal effects on auditory thresholds and tissue response in vivo. CPE-hydrogel formulations have potential for ototopical delivery of ciprofloxacin for the treatment of acute otitis media (AOM) and other middle ear diseases.

Microneedles: a valuable physical enhancer to increase transdermal drug delivery

Transdermal drug delivery offers an attractive alternative to the conventional drug delivery methods of oral administration and injection. However, the stratum corneum acts as a barrier that limits the penetration of substances through the skin. Recently, the use of micron-scale needles in increasing skin permeability has been proposed and shown to dramatically increase transdermal delivery. Microneedles have been fabricated with a range of sizes, shapes, and materials. Most in vitro drug delivery studies have shown these needles to increase skin permeability to a broad range of drugs that differ in molecular size and weight. In vivo studies have demonstrated satisfactory release of oligonucleotides and insulin and the induction of immune responses from protein and DNA vaccines. Microneedles inserted into the skin of human subjects were reported to be painless. For all these reasons, microneedles are a promising technology to deliver drugs into the skin. This review presents the main findings concerning the use of microneedles in transdermal drug delivery. It also covers types of microneedles, their advantages and disadvantages, enhancement mechanisms, and trends in transdermal drug delivery.

The effect of terpenes on percutaneous absorption of tiaprofenic acid gel

Tiaprofenic acid is a potent analgesic and nonsteroidal anti-inflammatory drug (NSAID) and like any other nonsteroidal anti-inflammatory drug, oral administration of the conventional dosage forms of tiaprofenic acid invariably causes gastrointestinal side effects. In an effort to eliminate these side effects while enhancing the drug concentration at the target tissue, an epidermal application of tiaprofenic acid seems to be an effective alternative drug delivery modality. This study attempts to demonstrate the influence of different terpenes (d-limonene, menthol and nerolidol) in various combinations of preparations on the percutaneous penetration of tiaprofenic acid from Carbopol(®) 940 based gel formulations (1%) in an ex vivo experiment using Franz-type diffusion cells. The enhancement effect of terpenes on skin absorption of tiaprofenic acid was further evaluated by an in vivo method in rats. Amongst the terpenes used, d-limonene was the most outstanding penetration enhancer that was reference to penetration of tiaprofenic acid through rat skin ex vivo. In vivo penetration study shows that the AUC₀(-)₄₈(h) was increased by about 10 fold by the addition of 5% d-limonene to the formulation. Histological studies show that d-limonene causes disruption on the skin surface and is responsible for enhanced penetration of tiaprofenic acid. Since tiaprofenic acid is known to cause gastrointestinal disturbances following systemic administration, topical formulations of tiaprofenic acid in gel form including 5% d-limonene could be suggested as an alternative.

Electroporation as an efficient physical enhancer for skin drug delivery

Transdermal drug delivery offers an attractive alternative to the conventional drug delivery methods of oral administration and injection. However, the stratum corneum acts as a barrier that limits the penetration of substances through the skin. Application of high-voltage pulses to the skin increases its permeability (electroporation) and enables the delivery of various substances into and through the skin. The application of electroporation to the skin has been shown to increase transdermal drug delivery. Moreover, electroporation, used alone or in combination with other enhancement methods, expands the range of drugs (small to macromolecules, lipophilic or hydrophilic, charged or neutral molecules) that can be delivered transdermally. The efficacy of transport depends on the electrical parameters and the physicochemical properties of drugs. The in vivo application of high-voltage pulses is well tolerated, but muscle contractions are usually induced. The electrode and patch design is an important issue to reduce the discomfort of the electrical treatment in humans. This review presents the main findings in the field of electroporation-namely, transdermal drug delivery. Particular attention is paid to proposed enhancement mechanisms and trends in the field of topical and transdermal delivery.

Design of Two Liquid Ibuprofen-Poloxamer-Limonene or Menthol Preparations for Dermal Administration

The purpose of our study was to prepare liquid forms of 20% ibuprofen in 30% poloxamer 407, while avoiding gel formation and to assess their drug diffusion-penetration (permeation) into the skin. Two series of poloxamer-based formulations were prepared, both containing ibuprofen and one of two terpenes: d-limonene and 1-menthol. A rheological characterization of all preparations made allowed their grouping in two modalities: gels and fluids. Data revealed a statistically superior enhanced permeation terpene-dependent of ibuprofen in fluid preparations, specially the one containing d-limonene. Cumulative permeation in 24 hr was 2500 micro g/cm(2) and 4500 micro g/cm(2) for the 1-menthol and d-limonene, respectively, for fluid preparations as compared with 2000 micro g/cm(2) and 1600 micro g/ cm(2) for d-limonene and 1-menthol on gels and only 1200 micro g/cm(2) of the control solution (p < 0.05). Results postulate that a liquid 30% poloxamer-based preparation of ibuprofen with d-limonene is possible and that it may be useful as a topical preparation of ibuprofen.

Effects of Enantiomer and Isomer Permeation Enhancers on Transdermal Delivery of Ligustrazine Hydrochloride

Enantiomers and isomers, such as D-limonene, L-limonene, and alpha-terpinene, were selected as enhancers. The effects and mechanisms of penetration enhancers on in vitro transdermal delivery of ligustrazine hydrochloride (LH) across hairless porcine dorsal skin were investigated. Transdermal fluxes of LH through porcine skin were determined in vitro by Franz-type diffusion cells. D-limonene, L-limonene, and alpha-terpinene could significantly promote the transdermal fluxes of LH, but no statistical difference (p > 0.05) between them was found. The lag time of L-limonene and alpha-terpinene were 2.55 and 2.20 times compared with that of D-limonene. Fourier transform-infrared (FTIR) was carried out to analyze the effects of enhancers on the biophysical natures of the stratum corneum (SC) and the permeation enhancement mechanism. FTIR spectra revealed that the changes of peak shift and peak area due to C-H stretching vibrations in the SC lipids were associated with the selected enhancers. All of them could perturb and extract the SC lipids to different extent and L-limonene showed obvious changes. Morphological changes of the skin treated with enhancers were monitored by a scanning electron microscope (SEM). The extraction of the SC lipids by the enhancers led to the disruption of SC and the desquamated SC flake. Apparent density (AD) was newly proposed to estimate the desquamated extent of SC flake. The results showed that the enantiomers and isomers enhanced the permeation of LH by pleiotropic mechanisms.

Poly(ethylene oxide)-poly(propylene oxide) block copolymer micelles as drug delivery agents: improved hydrosolubility, stability and bioavailability of drugs

The low solubility in biological fluids displayed by about 50% of the drugs still remains the main limitation in oral, parenteral, and transdermal administration. Among the existing strategies to overcome these drawbacks, inclusion of hydrophobic drugs into polymeric micelles is one of the most attractive alternatives. Amphiphilic poly(ethylene oxide)-poly(propylene oxide) block copolymers are thermoresponsive materials that display unique aggregation properties in aqueous medium. Due to their ability to form stable micellar systems in water, these materials are broadly studied as hydrosolubilizers for poorly water-soluble drugs. The present review provides a concise description of the most important applications of PEO-PPO-based copolymers in the Pharmaceutical Technology field as means for attaining improved solubility, stability, release, and bioavailability of drugs.

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.

Transdermal iontophoresis: combination strategies to improve transdermal iontophoretic drug delivery

For several decades, there has been interest in using the skin as a port of entry into the body for the systemic delivery of therapeutic agents. However, the upper layer of the skin, the stratum corneum, poses a barrier to the entry of many therapeutic entities. Given a compound, passive delivery rate is often dependent on two major physicochemical properties: the partition coefficient and solubility. The use of chemical enhancers and modifications of the thermodynamic activity of the applied drug are two frequently employed strategies to improve transdermal permeation. Chemical enhancers are known to enhance drug permeation by several mechanisms which include disrupting the organized intercellular lipid structure of the stratum corneum , 'fluidizing' the stratum corneum lipids , altering cellular proteins, and in some cases, extracting intercellular lipids . However, the resulting increase in drug permeation using these techniques is rather modest especially for hydrophilic drugs. A number of other physical approaches such as iontophoresis, sonophoresis, ultrasound and the use of microneedles are now being studied to improve permeation of hydrophilic as well as lipophilic drugs. This article presents an overview of the use of iontophoresis alone and in conjunction with other approaches such as chemical enhancement, electroporation, sonophoresis, and use of microneedles and ion-exchange materials.

Formulation of an HPMC Gel Drug Reservoir System with Ethanol-Water as a Solvent System and Limonene as a Penetration Enhancer for Enhancing in vitro Transdermal Delivery of Nicorandil

The objective of the present study was to formulate a hydroxypropyl methylcellulose (HPMC) gel drug reservoir system with ethanol-water as a solvent system and limonene as a penetration enhancer for enhancing the transdermal delivery of nicorandil so as to develop and fabricate a membrane-moderated transdermal therapeutic system (TTS). The in vitro permeation of nicorandil was determined across rat abdominal skin from a solvent system consisting of ethanol or various proportions of ethanol and water. The ethanol-water (70:30 v/v) solvent system that provided an optimal transdermal permeation was used in formulating an HPMC gel drug reservoir system with selected concentrations (0% w/w, 4% w/w, 6% w/w, 8% w/w or 10% w/w) of limonene as a penetration enhancer for further enhancement of transdermal permeation of nicorandil. The amount of nicorandil permeated in 24 h was found increased with an increase in the concentration of limonene in the drug reservoir system up to a concentration of 6% w/w, but beyond this concentration there was no further increase in the amount of drug permeated. The flux of nicorandil was 370.9 +/- 4.2 microg/cm2 x h from the drug reservoir system with 6% w/w of limonene, which is about 2.6 times the required flux to be obtained across rat abdominal skin for producing the desired plasma concentration for the predetermined period in humans. The results of a Fourier Transform Infrared study indicated that limonene enhanced the percutaneous permeation of nicorandil by partially extracting the stratum corneum lipids. It is concluded that the HPMC gel drug reservoir system prepared with a 70:30 v/v ethanol-water solvent system containing 6% w/w of limonene is useful in designing and fabricating a membrane-moderated TTS of nicorandil.

Evaluation of Percutaneous Absorption of Midazolam by Terpenes

Midazolam is a highly lipophilic drug that is widely used in preanesthetic medication. Recently, terpenes have been reported to show an enhancing effect on percutaneous absorption of drugs. The effect of terpenes (l-menthol, d-limonene, RS-(+/-)-beta-citronellol, geraniol) on the in vitro percutaneous absorption of midazolam through rat skin was evaluated using unjacketed Franz diffusion cells. Since midazolam is a lipophilic drug, percutaneous penetration is low and a percutaneous penetration enhancer is necessary for its percutaneous absorption. The terpenes (5%, w/v) in combination with 30% ethanol, and 20% propylene glycol significantly increased the percutaneous absorption of midazolam in comparison to the control. In vitro data suggested that d-limonene is the most effective enhancer among terpenes and other penetration enhancers such as Azone. In in vivo percutaneous absorption assays, the midazolam formulation using d-limonene could penetrate through rat skin, but the other terpenes could not penetrate. In conclusion, d-limonene in combination with ethanol can be used to enhance the percutaneous absorption of the highly lipophilic drug midazolam.