Retropharyngeal lipoma - a case report.

Lipomas of the retropharyngeal region are rare. They attain a large size before producing symptoms like dyspnoea and dysphagia. A case of lipoma in the retropharyngeal space is reported with characteristic radiological findings and surgical management.

Stability of insulin under iontophoretic conditions.

The present study focuses on the physical and chemical stability of insulin under iontophoretic conditions using HPLC, SDS-PAGE, RIA and biological assay. Influence of pH, concentration of insulin, current strength and duration of current application on the stability of insulin was studied. Anodal iontophoresis at pH 7.4 caused more than 80% degradation of insulin, while the degradation was minimal at pH 3.6. The degradation was not influenced by insulin concentration, but increase in current strength above 0.75 mA/cm2 or application of current for 12 h (at 0.5 mA/cm2) led to 80 and 20% degradation respectively. All the samples showed biological activity comparable to intact insulin.

Transdermal iontophoresis of insulin. VI. Influence of pretreatment with fatty acids on permeation across rat skin.

The delivery of large peptides through the skin poses a significant challenge, and various strategies are under active investigation for enhancing the transdermal permeation. For large peptides, it is difficult to achieve significant permeation using iontophoresis alone. Hence a combination of fatty acids with iontophoresis was hypothesized to result in higher enhancement than achieved with either of them alone. Saturated fatty acids and cis unsaturated fatty acids were studied in combination with iontophoresis using excised rat skin. The skin was pretreated for 2 h with an ethanolic (EtOH) solution of 5% w/v or v/v fatty acids, namely lauric acid (LA), oleic acid (OA), linoleic acid (LOA) and linolenic acid (LLA), followed by either passive or iontophoretic permeation (0.5 mA/cm2 for 6 h). Fourier transform infrared spectroscopy (FT-IR) was used to investigate the biophysical changes on treatment with fatty acid/EtOH or neat fatty acid, mainly focusing on the infrared region at 2,920, 1,710 and 1,720 cm(-1). Unsaturated fatty acids showed higher enhancement than LA, and the enhancement increased with the number of double bonds. On the other hand, in the presence of iontophoresis, LA/EtOH showed the highest enhancement. Neat LOA did not show any significant difference (p > 0.05) compared to the LOA/EtOH combination. FT-IR studies revealed that fatty acids act by interacting with the skin lipids. All the fatty acids showed synergistic enhancement when combined with iontophoresis. The flux enhancement was highest with LA, which in the presence of iontophoresis showed 20 times enhancement of insulin flux in comparison to passive flux and 9 times enhancement as compared to iontophoresis alone. Flux enhancement of unsaturated fatty acids was in the following decreasing order LOA > OA > LLA.

Transdermal iontophoresis of insulin: III. Influence of electronic parameters.

Transdermal iontophoresis is a physical enhancement strategy primarily for charged molecules and offers a number of advantages for the delivery of peptides and proteins. The singular advantage of iontophoresis lies in the precise control of dose by manipulating the current protocol. The objective of the present investigation was to understand the role of electronic parameters on iontophoretic transport of large peptides using insulin as a model peptide. Ex vivo permeation experiments were conducted using excised rat skin and the influence of varying current strengths, duration, on/off ratios and switching iontophoresis on insulin permeation were studied. High performance liquid chromatography (HPLC), polyacrylamide gel electrophoresis (SDS-PAGE) and thin layer chromatography (TLC) were used to assess the electrochemical stability of insulin; while Fourier transform infra-red (FT-IR) spectroscopy and thermogravimetric analysis (TGA) were used to understand the biophysical changes in skin during iontophoresis. The permeation of insulin was found to increase as a function of current strength and duration of current application. Skin barrier integrity and electrochemical stability of insulin was dependent on the charge applied during iontophoresis. FT-IR spectroscopy and TGA studies showed that the skin hydration increased with increase in the charge applied and thus facilitated the transport of insulin. Periodic iontophoresis did not show any significant difference in insulin permeation compared with continuous current application; 1:1 on/off ratio resulted in higher amount of insulin permeation, while flux was highest with mixed duty cycle. Switching iontophoresis was useful in reducing the pH shift and in improving the electrochemical stability of insulin at pH 3.6 and 7.4, respectively. The electroosmotic flow was influenced by the pH of the donor medium, as well as by the electrode polarity during switching and non-switching iontophoresis. Overall, the study demonstrates the issues related to the optimization of electronic parameters for the iontophoretic delivery of a large peptide.

Insulin therapies - past, present and future.

The discovery of insulin is one of the greatest milestones in medical history. This discovery revolutionized the use of peptides and proteins as therapeutic agents. For more than six decades, insulin from different animal sources was used, until the breakthrough in biotechnology made it possible to produce human insulin in sufficient amounts. The evolution of the biotechnological era gave rise to modified insulins to solve some of the bottlenecks in insulin therapy. Efforts are currently focused towards developing non-invasive insulin delivery systems, and there are several competing technologies in different stages of development. The next few years will see several novel approaches to mimic the endogenous release and kinetics of insulin, and also many improved analogues designed to achieve better control and effective treatment of diabetes.

Polymers in drug delivery.

Advances in polymer science have led to the development of several novel drug-delivery systems. A proper consideration of surface and bulk properties can aid in the designing of polymers for various drug-delivery applications. Biodegradable polymers find widespread use in drug delivery as they can be degraded to non-toxic monomers inside the body. Novel supramolecular structures based on polyethylene oxide copolymers and dendrimers are being intensively researched for delivery of genes and macromolecules. Hydrogels that can respond to a variety of physical, chemical and biological stimuli hold enormous potential for design of closed-loop drug-delivery systems. Design and synthesis of novel combinations of polymers will expand the scope of new drug-delivery systems in the future.

Drug delivery: an odyssey of 100 years.

Drug delivery has metamorphosed from the concept of a pill to molecular medicine in the past 100 years. Better appreciation and integration of pharmacokinetic and pharmacodynamic principles in design of drug delivery systems has led to improved therapeutic efficacy. A greater understanding of the molecular transport in relation to physico-chemical properties has led to the evolution of a biopharmaceutics classification system, which should be a future road map, governing drug design, development and delivery. While drugs belonging to class I and II will be delivered by established platform technologies, novel delivery strategies will evolve and mature to realize the potential of 'new generation' biotech and non biotech drugs belonging to class III and IV, respectively.

Nicotine transdermal systems: pharmaceutical and clinical aspects.

Smoking is creating a burden on the healthcare budgets all over the world. Management of nicotine dependence is difficult due to the so-called pleasurable effects experienced by smokers. Among the various treatment approaches, nicotine replacement therapy, where nicotine from cigarettes is replaced with nicotine from a relatively safer delivery vehicle, has been successful. Transdermal delivery of nicotine is an effective type of nicotine replacement therapy due to inherent pharmacokinetic advantages over other routes of delivery. Several nicotine transdermal delivery systems are available to suit the varying needs of smokers and have been found to be clinically patient friendly and well tolerated. This review focuses on the various clinical and pharmaceutical aspects of nicotine with special emphasis on transdermal delivery systems.

Transdermal iontophoresis revisited.

Iontophoresis evolved as a transdermal enhancement technique in the 20th century, primarily for the delivery of large and charged molecules. Significant achievements have been made in the understanding of underlying mechanisms of iontophoresis and these have contributed to the rational development of iontophoretic delivery systems. The major challenges in this area are the development of portable, cost effective devices and suitable semi-solid formulations that are compatible with the device and the skin. Some of the obstacles in transdermal iontophoresis can be overcome by combining iontophoresis with other physical and chemical enhancement techniques for the delivery of macromolecules. Iontophoresis also offers an avenue for extracting information from the body through the use of reverse iontophoresis, which has potential application in diagnosis and monitoring. The current research is focussed towards resolving the skin toxicity issues and other problems in order to make this technology a commercial reality.

Transdermal iontophoresis. Part II: Peptide and protein delivery.

The advent of sophisticated biotechnological processes has generated an interest in peptide and protein pharmaceuticals. However, the rapid developments in biotechnology are not matched by the developments in the delivery of these molecules. Presently, most of the peptides and proteins are delivered by parenteral route due to their poor oral bioavailability. The inherent discomforts associated with the parenteral therapy has prompted investigations into other nonparenteral routes and drug delivery techniques. Transdermal iontophoresis is one such technique showing good promise in the controlled and enhanced delivery of peptides and proteins. It offers noninvasive, continuous, pulsatile delivery as well as preprogramed complex dosing regimens. Miniature battery powered and wearable patches for peptides and proteins are expected to be on the market by the turn of this century. In continuation of our earlier review, this review explores the potential of transdermal iontophoresis for the delivery of peptides and proteins with the main focus on the suitability of the technique along with the factors to be considered in the design of this drug delivery system and its future prospects.

Transdermal iontophoresis. Part I: Basic principles and considerations.

The skin has increasingly become a route for the delivery of drugs with a range of compounds being considered for transdermal delivery generating a great deal of interest in this area of research. The passive delivery of most compounds across the skin is limited due to the barrier properties afforded by stratum corneum, the outermost layer of the skin. Transdermal iontophoresis is an effective technique for physically facilitating the transport of permeants across the skin by using electromotive force. It is being extensively explored as a potential means for delivery of hydrophilic, large and charged molecules and is also believed to be a future method of choice for peptides and proteins. In this context, this review focuses mainly on the basic principles and considerations of transdermal iontophoresis with particular emphasis on modeling, devices and parameters influencing transdermal iontophoresis.