Alternative routes of insulin delivery

Fabrication of two-layer dissolving polyvinylpyrrolidone microneedles with different molecular weights for in vivo insulin transdermal delivery

Fabrication of two-layer dissolving polyvinylpyrrolidone microneedles for in vivo insulin transdermal delivery.

Pharmacy Update

The prevalence of diabetes mellitus has increased to more than 20 million people in the United States, and current estimates indicate that one third of all Americans born in the year 2000 will develop diabetes mellitus in their lifetime. The need for diabetes therapies offering improved glucose control by mimicking normal physiological properties of glucose metabolism and improving on logistics such as ease of use, self-management, monitoring, and delivery is clear. This article, part 2 of a 3-part series, reviews newer injectable insulin preparations and examines the first-to-market orally inhaled dry powdered insulin (IDPI). The information provided is tailored to diabetes educators and includes mechanism of action, pharmacokinetics, drug interactions, clinical trials, dosage and administration guidelines, side effects, and educational pearls for each insulin discussed. A detailed patient case designed to acquaint the reader with these newer insulin products and provide an understanding of clinical issues to consider when providing diabetes education to patients is included.

Stimuli-Responsive Delivery of Therapeutics for Diabetes Treatment

Diabetic therapeutics, including insulin and glucagon-like peptide 1 (GLP-1), are essential for diabetic patients to regulate blood glucose levels. However, conventional treatments that are based on subcutaneous injections are often associated with poor glucose control and a lack of patient compliance. In this review, we focus on the different stimuli-responsive systems to deliver therapeutics for diabetes treatment to improve patient comfort and prevent complications. Specifically, the pH-responsive systems for oral drug delivery are introduced first. Then, the closed-loop glucose-responsive systems are summarized based on different glucose-responsive moieties, including glucose oxidase (GOx), glucose binding protein (GBP), and phenylboronic acid (PBA). Finally, the on-demand delivery systems activated by external remote triggers are also discussed. We conclude by discussing advantages and limitations of current strategies, as well as future opportunities and challenges in this area.

Pre-formulation and systematic evaluation of amino acid assisted permeability of insulin across in vitro buccal cell layers

The aim of this work was to investigate alternative safe and effective permeation enhancers for buccal peptide delivery. Basic amino acids improved insulin solubility in water while 200 and 400 μg/mL lysine significantly increased insulin solubility in HBSS. Permeability data showed a significant improvement in insulin permeation especially for 10 μg/mL of lysine (p < 0.05) and 10 μg/mL histidine (p < 0.001), 100 μg/mL of glutamic acid (p < 0.05) and 200 μg/mL of glutamic acid and aspartic acid (p < 0.001) without affecting cell integrity; in contrast to sodium deoxycholate which enhanced insulin permeability but was toxic to the cells. It was hypothesized that both amino acids and insulin were ionised at buccal cavity pH and able to form stable ion pairs which penetrated the cells as one entity; while possibly triggering amino acid nutrient transporters on cell surfaces. Evidence of these transport mechanisms was seen with reduction of insulin transport at suboptimal temperatures as well as with basal-to-apical vectoral transport, and confocal imaging of transcellular insulin transport. These results obtained for insulin are the first indication of a possible amino acid mediated transport of insulin via formation of insulin-amino acid neutral complexes by the ion pairing mechanism.

Formulation of two-layer dissolving polymeric microneedle patches for insulin transdermal delivery in diabetic mice

Dissolving microneedles (MNs) display high efficiency in delivering poorly permeable drugs and vaccines. Here, two-layer dissolving polymeric MN patches composed of gelatin and sodium carboxymethyl cellulose (CMC) were fabricated with a two-step casting and centrifuging process to localize the insulin in the needle and achieve efficient transdermal delivery of insulin. In vitro skin insertion capability was determined by staining with tissue-marking dye after insertion, and the real-time penetration depth was monitored using optical coherence tomography. Confocal microscopy images revealed that the rhodamine 6G and fluorescein isothiocyanate-labeled insulin (insulin-FITC) can gradually diffuse from the puncture sites to deeper tissue. Ex vivo drug-release profiles showed that 50% of the insulin was released and penetrated across the skin after 1 h, and the cumulative permeation reached 80% after 5 h. In vivo and pharmacodynamic studies were then conducted to estimate the feasibility of the administration of insulin-loaded dissolving MN patches on diabetic mice for glucose regulation. The total area above the glucose level versus time curve as an index of hypoglycemic effect was 128.4 ± 28.3 (% h) at 0.25 IU/kg. The relative pharmacologic availability and relative bioavailability (RBA) of insulin from MN patches were 95.6 and 85.7%, respectively. This study verified that the use of gelatin/CMC MN patches for insulin delivery achieved a satisfactory RBA compared to traditional hypodermic injection and presented a promising device to deliver poorly permeable protein drugs for diabetic therapy. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 84-93, 2017.

Review: Diabetes and insulin therapy in older people

Concerns about hypoglycaemia, plus lack of evidence of benefit, contributed to underutilisation of insulin for older people with type 2 diabetes in the past. Following the UKPDS it is clear that many elderly patients treated with diet and oral antidiabetic agents will develop beta-cell failure and will be at risk of worsening glycaemic control with reduced well-being unless insulin is considered. Following diabetes diagnosis, the mainstay of treatment will be dietary control and exercise together with management of cardiovascular risk factors. When glycaemic control deteriorates oral agents will be needed. However, whereas in the past insulin was seen as a last resort for older type 2 patients there is support for considering its early use in selected older people with preserved cognitive function and poor glycaemic control, as well as for frail older people with weight loss and poor quality of life. The regimens of choice may include a combination of basal insulin with oral agents or twice-daily combinations of premixed short and intermediate acting insulin. The development of insulin analogues with their associated reduced risk of hypoglycaemia may also herald a new era of insulin treatment for older people.

Transition from passive to active targeting of oral insulin nanomedicines: enhancement in bioavailability and glycemic control in diabetes

Oral insulin nanomedicines are effective tools for therapy and management of both Type I and Type II diabetes. This review summarizes the various nanocarriers developed so far in the literature for oral delivery of insulin. It includes lipid-based (i.e., solid lipid nanoparticles and liposomes) and polymeric-based insulin nanomedicines (i.e., chitosan nanoparticles, alginate nanoparticles, dextran nanoparticles and nanoparticles of synthetic polymers) for sustained, controlled and targeted oral delivery of insulin. Mainly, goblet cell-targeting, vitamin B12 receptor-targeting, folate receptor-targeting and transferrin receptor-targeting aspects were focused. Currently, passive and active targeting approaches of oral insulin nanomedicines have improved the oral absorption of insulin and its bioavailability (up to 14%) that produced effective glycaemic control in in vivo models. These results indicate a promising future of oral insulin nanomedicines for the treatment of diabetes.

The function and performance of aqueous aerosol devices for inhalation therapy

OBJECTIVES

In this review paper, we explore the interaction between the functioning mechanism of different nebulizers and the physicochemical properties of the formulations for several types of devices, namely jet, ultrasonic and vibrating-mesh nebulizers; colliding and extruded jets; electrohydrodynamic mechanism; surface acoustic wave microfluidic atomization; and capillary aerosol generation.

KEY FINDINGS

Nebulization is the transformation of bulk liquids into droplets. For inhalation therapy, nebulizers are widely used to aerosolize aqueous systems, such as solutions and suspensions. The interaction between the functioning mechanism of different nebulizers and the physicochemical properties of the formulations plays a significant role in the performance of aerosol generation appropriate for pulmonary delivery. Certain types of nebulizers have consistently presented temperature increase during the nebulization event. Therefore, careful consideration should be given when evaluating thermo-labile drugs, such as protein therapeutics. We also present the general approaches for characterization of nebulizer formulations.

SUMMARY

In conclusion, the interplay between the dosage form (i.e. aqueous systems) and the specific type of device for aerosol generation determines the effectiveness of drug delivery in nebulization therapies, thus requiring extensive understanding and characterization.

Pursuit of a perfect insulin

Insulin remains indispensable in the treatment of diabetes, but its use is hampered by its narrow therapeutic index. Although advances in peptide chemistry and recombinant DNA-based macromolecule synthesis have enabled the synthesis of structurally optimized insulin analogues, the growing epidemics of obesity and diabetes have emphasized the need for diabetes therapies that are more efficacious, safe and convenient. Accordingly, a broad set of drug candidates, targeting hyperglycaemia plus other disease abnormalities, is now progressing through the clinic. The development of an insulin therapy that is responsive to glucose concentration remains an ultimate goal, with initial prototypes now reaching the proof-of-concept stage. Simultaneously, the first alternatives to injectable delivery have progressed to registration.

Needle-free injection of insulin powder: delivery efficiency and skin irritation assessment

Insulin is widely used in treating diabetes, but still needs to be administered by needle injection. This study investigated a new needle-free approach for insulin delivery. A portable powder needleless injection (PNI) device with an automatic mechanical unit was designed. Its efficiency in delivering insulin was evaluated in alloxan-induced diabetic rabbits. The skin irritation caused by the device was investigated and the results were analyzed in relation to aerodynamic parameters. Inorganic salt-carried insulin powders had hypoglycemic effects, while raw insulin powders were not effective when delivered by PNI, indicating that salt carriers play an important role in the delivery of insulin via PNI. The relative delivery efficiency of phosphate-carried insulin powder using the PNI device was 72.25%. A safety assessment test showed that three key factors (gas pressure, cylinder volume, and nozzle distance) were related to the amount of skin irritation caused by the PNI device. Optimized injection conditions caused minimal skin lesions and are safe to use in practice. The results suggest that PNI has promising prospects as a novel technology for delivering insulin and other biological drugs.

Why most oral insulin formulations do not reach clinical trials

Oral insulin able to induce an efficient antihyperglycemic effect either to replace or complement diabetes mellitus therapy is the major goal of health providers, governments and diabetic patients. Oral therapy is associated not only with the desire to exclude needles from the daily routine of diabetic patient but also with the physiological provision of insulin they would get. Despite numerous efforts over the past few decades to develop insulin delivery systems, there is still no commercially available oral insulin. The reasons why the formulations developed to administer insulin orally fail to reach clinical trials are critically discussed in this review. The principal features of nanoformulations used so far are also addressed as well as the undergoing clinical trials.

VB12-coated Gel-Core-SLN containing insulin: Another way to improve oral absorption

To improve the oral absorption of insulin, a novel carrier of Vitamin B12 (VB12) gel core solid lipid nanopaticles (Gel-Core-SLN, GCSLN) was designed with a gel core, lipid matrix and VB12-coated surface. VB12-stearate was synthesized and characterized by infrared spectroscopy (IR), nuclear magnetic resonance spectroscopy (NMR) and mass spectrometry (MS). Sol-gel conversion following ultrasonic heating and double emulsion technology were combined to implant the insulin-containing gel into solid lipid nanoparticles (SLN). The influence of the mode of administration, food, the amount of VB12-stearate and the particle size on the oral absorption of insulin incorporated in the VB12-GCSLN was investigated. The determined partition coefficient (LogP) of VB12-stearate in a dichloromethane (DCM)-water system was 3.4. This new structure of VB12-GCSLN had higher insulin encapsulation efficiency (EE) of 55.9%, a lower burst release of less than 10% in the first 2h. In vivo studies demonstrated that stronger absorption of insulin with a relative pharmacological availability (PA) of 9.31% compared with the normal insulin-loaded SLN and GCSLN and fairly stable blood glucose levels up to 12h were maintained without any sharp fluctuations. This study suggests that VB12-GCSLN containing insulin appears to be a promising nano carrier for oral delivery of biomacromolecules with relatively high pharmacological availability.

Pharmacokinetic Model of the Transport of Fast-Acting Insulin From the Subcutaneous and Intradermal Spaces to Blood

Pharmacokinetic (PK) models describing the transport of insulin from the injection site to blood assist clinical decision making and are part of in silico platforms for developing and testing of insulin delivery strategies for treatment of patients with diabetes. The ability of these models to accurately describe all facets of the in vivo insulin transport is therefore critical for their application. Here, we propose a new model of fast-acting insulin analogs transport from the subcutaneous and intradermal spaces to blood that can accommodate clinically observed biphasic appearance and delayed clearance of injected insulin, 2 phenomena that are not captured by existing PK models. To develop the model we compare 9 insulin transport PK models which describe hypothetical insulin delivery pathways potentially capable of approximating biphasic appearance of exogenous insulin. The models are tested with respect to their ability to describe clinical data from 10 healthy volunteers which received 1 subcutaneous and 2 intradermal insulin injections on 3 different occasions. The optimal model, selected based on information and posterior identifiability criteria, assumes that insulin is delivered at the administrative site and is then transported to the bloodstream via 2 independent routes (1) diffusion-like process to the blood and (2) combination of diffusion-like processes followed by an additional compartment before entering the blood. This optimal model accounts for biphasic appearance and delayed clearance of exogenous insulin. It agrees better with the clinical data as compared to commonly used models and is expected to improve the in silico development and testing of insulin treatment strategies, including artificial pancreas systems.

Effect of mucoadhesive polymers on the in vitro performance of insulin-loaded silica nanoparticles: Interactions with mucin and biomembrane models

The present paper focuses on the development and characterization of silica nanoparticles (SiNP) coated with hydrophilic polymers as mucoadhesive carriers for oral administration of insulin. SiNP were prepared by sol-gel technology under mild conditions and coated with different hydrophilic polymers, namely, chitosan, sodium alginate or poly(ethylene glycol) (PEG) with low and high molecular weight (PEG 6000 and PEG 20000) to increase the residence time at intestinal mucosa. The mean size and size distribution, association efficiency, insulin structure and insulin thermal denaturation have been determined. The mean nanoparticle diameter ranged from 289 nm to 625 nm with a PI between 0.251 and 0.580. The insulin association efficiency in SiNP was recorded above 70%. After coating, the association efficiency of insulin increased up to 90%, showing the high affinity of the protein to the hydrophilic polymer chains. Circular dichroism (CD) indicated that no conformation changes of insulin structure occurred after loading the peptide into SiNP. Nano-differential scanning calorimetry (nDSC) showed that SiNP shifted the insulin endothermic peak to higher temperatures. The influence of coating on the interaction of nanoparticles with dipalmitoylphosphatidylcholine (DPPC) biomembrane models was also evaluated by nDSC. The increase of ΔH values suggested a strong association of non-coated SiNP and those PEGylated nanoparticles coated with DPPC polar heads by forming hydrogen bonds and/or by electrostatic interaction. The mucoadhesive properties of nanoparticles were examined by studying the interaction with mucin in aqueous solution. SiNP coated with alginate or chitosan showed high contact with mucin. On the other hand, non-coated SiNP and PEGylated SiNP showed lower interaction with mucin, indicating that these nanoparticles can interdiffuse across mucus network. The results of the present work provide valuable data in assessing the in vitro performance of insulin-loaded SiNP coated with mucoadhesive polymers.

How to overcome the limitations of current insulin administration with new non-invasive delivery systems

Non-invasive insulin delivery systems have potential to overcome the most pressing problem regarding effective treatment of diabetic patients: therapy compliance. To overcome this disadvantage, non-invasive routes such as oral, buccal, pulmonary, nasal and transdermal have been proposed. These new routes of insulin administration may help to suppress hypoglycemia episodes and aid to control weight gain and post-meal glucose. Despite all efforts the invasive route remains preferential, since studies on insulin administration by non-invasive routes conducted to date have not demonstrated clinical efficacy and safety, including some products introduced in the market. Therefore, the aim of this review is to make an update of the current state of administration of insulin by non-invasive routes as alternatives to the conventional invasive route.

Developing accurate models of the human airways

Objectives

Particle delivery to the airways is an attractive prospect for many potential therapeutics, including vaccines. Developing strategies for inhalation of particles provides a targeted, controlled and non-invasive delivery route but, as with all novel therapeutics, in vitro and in vivo testing are needed prior to clinical use. Whilst advanced vaccine testing demands the use of animal models to address safety issues, the production of robust in vitro cellular models would take account of the ethical framework known as the 3Rs (Replacement, Reduction and Refinement of animal use), by permitting initial screening of potential candidates prior to animal use. There is thus a need for relevant, realistic in vitro models of the human airways.

Key findings

Our laboratory has designed and characterised a multi-cellular model of human airways that takes account of the conditions in the airways and recapitulates many salient features, including the epithelial barrier and mucus secretion.

Summary

Our human pulmonary models recreate many of the obstacles to successful pulmonary delivery of particles and therefore represent a valid test platform for screening compounds and delivery systems.

Design and in silico evaluation of an intraperitoneal-subcutaneous (IP-SC) artificial pancreas

Prandial glucose regulation is a major challenge for the artificial pancreas using subcutaneous insulin (without a feedforward bolus) due to insulin's slow absorption-peak (50-60 min). Intraperitoneal insulin, with a fast absorption peak (20-25 min), has been suggested as an alternative to address these limitations. An artificial pancreas using intraperitoneal insulin was designed and evaluated on 100 in silico subjects and compared with two designs using subcutaneous insulin with and without a feedforward bolus, following the three meal (40-70 g-carbohydrates) evaluation protocol. The design using intraperitoneal insulin resulted in a significantly lower postprandial blood glucose peak (38 mg/dL) and longer time in the clinically accepted region (13%) compared to the design using subcutaneous insulin without a feedforward bolus and comparable results to a subcutaneous feedforward bolus design. This superior regulation with minimal user interaction may improve the quality of life for people with type 1 diabetes mellitus.

Surface engineering of silica nanoparticles for oral insulin delivery: characterization and cell toxicity studies

The present work aimed at studying the interaction between insulin and SiNP surfaced with mucoadhesive polymers (chitosan, sodium alginate or polyethylene glycol) and the evaluation of their biocompatibility with HepG2 and Caco-2 cell lines, which mimic in vivo the target of insulin-loaded nanoparticles upon oral administration. Thus, a systematic physicochemical study of the surface-modified insulin-silica nanoparticles (Ins-SiNP) using mucoadhesive polymers has been described. The surfacing of nanoparticle involved the coating of silica nanoparticles (SiNP) with different mucoadhesive polymers, to achieve high contact between the systems and the gut mucosa to enhance the oral insulin bioavailability. SiNP were prepared by a modified Stöber method at room temperature via hydrolysis and condensation of tetraethyl orthosilicate (TEOS). Interaction between insulin and nanoparticles was assessed by differential scanning calorimetry (DSC), X-ray and Fourier-transform infrared (FTIR) studies. The high efficiency of nanoparticles' coating resulted in more stable system. FTIR spectra of insulin-loaded nanoparticles showed amide absorption bands which are characteristic of α-helix content. In general, all developed nanoparticles demonstrated high biocompatible, at the tested concentrations (50-500 μg/mL), revealing no or low toxicity in the two human cancer cell lines (HepG2 and Caco-2). In conclusion, the developed insulin-loaded SiNP surfaced with mucoadhesive polymers demonstrated its added value for oral administration of proteins.

In vivo evaluation of thiolated chitosan tablets for oral insulin delivery

Chitosan-6-mercaptonicotinic acid (chitosan-6-MNA) is a thiolated chitosan with strong mucoadhesive properties and a pH-independent reactivity. This study aimed to evaluate the in vivo potential for the oral delivery of insulin. The comparison of the nonconjugated chitosan and chitosan-6-MNA was performed on several studies such as mucoadhesion, release, and in vivo studies. Thiolated chitosan formulations were both about 80-fold more mucoadhesive compared with unmodified ones. The thiolated chitosan tablets showed a sustained release for 5 h for the polymer of 20 kDa and 8 h for the polymer of 400 kDa. Human insulin was quantified in rats' plasma by means of ELISA specific for human insulin with no cross-reactivity with the endogenous insulin. In vivo results showed thiolation having a tremendous impact on the absorption of insulin. The absolute bioavailabilities were 0.73% for chitosan-6-MNA of 20 kDa and 0.62% for chitosan-6-MNA 400 kDa. The areas under the concentration-time curves (AUC) of chitosan-6-MNA formulations compared with unmodified chitosan were 4.8-fold improved for the polymer of 20 kDa and 21.02-fold improved for the polymer of 400 kDa. The improvement in the AUC with regard to the most promising aliphatic thiomer was up to 6.8-fold. Therefore, chitosan-6-MNA represents a promising excipient for the oral delivery of insulin.

Emerging Trends in Noninvasive Insulin Delivery

This paper deals with various aspects of oral insulin delivery system. Insulin is used for the treatment of diabetes mellitus, which is characterized by the elevated glucose level (above the normal range) in the blood stream, that is, hyperglycemia. Oral route of administration of any drug is the most convenient route. Development of oral insulin is still under research. Oral insulin will cause the avoidance of pain during the injection (in subcutaneous administration), anxiety due to needle, and infections which can be developed. Different types of enzyme inhibitors, like sodium cholate, camostat, mesilate, bacitracin, leupeptin, and so forth, have been used to prevent insulin from enzymatic degradation. Subcutaneous route has been used for administration of insulin, but pain and itching at the site of administration can occur. That is why various alternative routes of insulin administration like oral route are under investigation. In this paper authors summarized advancement in insulin delivery with their formulation aspects.

Particle designs for the stabilization and controlled-delivery of protein drugs by biopolymers: a case study on insulin

Natural biopolymers have attracted considerable interest for the development of delivery systems for protein drugs owing to their biocompatibility, non-toxicity, renewability and mild processing conditions. This paper offers an overview of the current status and future perspectives of particle designs using biopolymers for the stabilization and controlled-delivery of a model protein drug--insulin. We first describe the design criteria for polymeric encapsulation and subsequently classify the basic principles of particle fabrication as well as the existing particle designs for oral insulin encapsulation. The performances of these existing particle designs in terms of insulin stability and in vitro release behavior in acidic and alkaline media, as well as their in vivo performance are compared and reviewed. This review forms the basis for future works on the optimization of particle design and material formulation for the development of an improved oral delivery system for protein drugs.

A single-blind, placebo-controlled, dose-ranging trial of oral hepatic-directed vesicle insulin add-on to oral antidiabetic treatment in patients with type 2 diabetes mellitus

The dose response of postprandial plasma glucose (PPG) to add-on, premeal oral hepatic-directed vesicle-insulin (HDV-I), an investigational lipid bio-nanoparticle hepatocyte-targeted insulin delivery system, was evaluated in a 3-test-meal/day model in type 2 diabetes patients. The single-blind, placebo-controlled, dose-escalating trial enrolled 6 patients with HbA(1c) 8.6 ± 2.0% (70.0 ± 21.9 mmol/mol) and on stable metformin therapy. Patients received oral HDV-I capsules daily 30 minutes before breakfast, lunch, and dinner as follows: placebo capsules, 0.05, 0.1, 0.2, and 0.4 U/kg on days 1, 2, 3, 4, and 5, respectively. Outcome measures were PPG and incremental PPG area under the concentration-time curve (AUC). All 4 doses of oral HDV-I statistically significantly lowered mean PPG (P ≤ .0110 each) and incremental PPG (P ≤ .0352 each) AUC compared to placebo. A linear dose response was not observed. The 0.05 U/kg dose was the minimum effective dose in the dosage range studied. Three adverse events unrelated to treatment were observed. Add-on oral HDV-I 0.05-0.4 U/kg significantly lowered PPG excursions and the dose response curve was flat. These results are consistent with the lack of a linear dose response between portal and systemic plasma insulin concentrations in previous animal and human studies. Oral HDV-I was safe and well tolerated.

Intradermal insulin delivery: a promising future for diabetes management

The incidence of insulinopenic diabetes mellitus is constantly increasing, and in addition, approximately a third of all hyperinsulinemic diabetic patients develop insulinopenia. Optimal glycemic control is essential to minimize the risk for diabetes-induced complications, but the majority of diabetic patients fail to achieve proper long-term glucose levels even in clinical trials, and even more so in clinical practice. Compliance with a treatment regimen is likely to be higher if the procedure is simple, painless, and discreet. Thus, insulin has been suggested for nasal, gastrointestinal, and inhalation therapy, but so far with considerable downsides in effect, side effects, or patient acceptance. The stratum corneum is the main barrier preventing convenient drug administration without the drawbacks of subcutaneous injections. Recently, devices with miniaturized needles have been developed that combine the simplicity and discretion of patch-based treatments, but with the potential of peptide and protein administration. As this review describes, initial comparisons with subcutaneous administration now suggest microneedle patches for active insulin delivery are efficient in maintaining glycemic control. Hollow microneedle technology could also prove to be efficient in systemic as well as local delivery of other macromolecular drugs, such as vaccines.

Drug transport mechanism of oral antidiabetic nanomedicines

CONTEXT

Over the last few decades, extensive efforts have been made worldwide to develop nanomedicine delivery systems, especially via oral route for antidiabetic drugs. Absorption of insulin is hindered by epithelial cells of gastrointestinal tract, acidic gastric pH and digestive enzymes.

EVIDENCE ACQUISITION

Recent reports have identified and explained the beneficial role of several structural molecules like mucoadhesive polymers (polyacrylic acid, sodium alginate, chitosan) and other copolymers for the efficient transport and release of insulin to its receptors.

RESULTS

Insulin nanomedicines based on alginate-dextran sulfate core with a chitosan-polyethylene glycol-albumin shell reduced glycaemia in a dose dependent manner. Orally available exendin-4 formulations exerted their effects in a time dependent manner. Insulin nanoparticles formed by using alginate and dextran sulfate nucleating around calcium and binding to poloxamer, stabilized by chitosan, and subsequently coated with albumin showed a threefold increase of the hypoglycemic effect in comparison to free insulin in animal models. Solid lipid nanoparticles showed an enhancement of the bioavailability of repaglinide (RG) within optimized solid lipid nanoparticle formulations when compared with RG alone.

CONCLUSIONS

Nanoparticles represent multiparticulate delivery systems designed to obtain prolonged or controlled drug delivery and to improve bioavailability as well as stability. Nanoparticles can also offer advantages like limiting fluctuations within therapeutic range, reducing side effects, protecting drugs from degradation, decreasing dosing frequency, and improving patient compliance and convenience.

How can we bring high drug doses to the lung?

In the last decades, dry powder inhalation has become a very attractive option for pulmonary drug delivery to treat lung diseases like cystic fibroses and lung infections. In contrast to the traditional pulmonary application of drugs for asthma and chronic obstructive pulmonary disease, these therapies require higher lung doses to be administered. The developments and improvements toward high dose powder pulmonary drug delivery are summarized and discussed in this chapter. These include the invention and improvement of novel inhaler devices as well as the further development of formulation principles and new powder engineering methods. The implementation of these strategies is subsequently described for some prototypes and formulations in research and development stage as well as for already marketed dry powder products. Finally, possible adverse effects that can occur after inhalation of high powder doses are shortly addressed.

Noninvasive insulin delivery: the great potential of cell-penetrating peptides

Insulin, a potent therapeutic peptide used in the treatment of diabetes, is administered to patients via subcutaneous injections because of the poor pharmacokinetics associated with alternative routes of administration such as oral, nasal and pulmonary delivery. Noninvasive nasal and oral formulations are appealing to patients who need consecutive daily treatments of insulin. However, to achieve mucosal absorption of insulin via oral or nasal administration, two barriers must be overcome: the impermeability of insulin through the epithelial membranes and local digestion and enzymatic degradation. Cell-penetrating peptides (CPPs), which efficiently bring exogenous proteins and nucleic acids into cells, have great potential to facilitate insulin permeation from the intestinal lumen or nasal cavity into systemic circulation via efficient uptake by epithelial cells. In fact, the coadministration of insulin with the peptide penetratin, a typical CPP, increased intestinal and nasal insulin bioavailability to 35 and 50%, respectively. In this review, the authors describe recent findings using this novel CPP-based formulation for noninvasive delivery of insulin.

Optimization of the fine particle fraction of a lyophilized lysozyme formulation for dry powder inhalation

PURPOSE

A new dry powder inhalation technology creates inhalable particles from a coherent lyophilized bulk at the time of inhalation. The aim of this study was to evaluate several approaches to improve the fine particle fraction (FPF) and to understand underlying mechanisms.

METHODS

Lysozyme was chosen as model drug. Phenylalanine and valine were added, and the freezing process was varied. Lyophilisate characteristics as well as aerosolization behavior was analyzed.

RESULTS

The addition of the crystalline amino acids rendered a dose independent three-fold increase of the FPF. This is possibly due to enhanced fracture properties of the lyophilisates upon impact of the air stream and reduced particle agglomeration/cohesion caused by a rougher surface. This positive effect was well preserved over 3 months of storage. The structure of the lyophilisate was influenced by the freezing process which in turn affected the aerosolization behavior. Liquid nitrogen and vacuum-induced freezing performed best, doubling the FPF. The special cake morphology with elongated channels enabled easy disintegration. The resulting large porous particles comprise a low density being advantageous for a high FPF.

CONCLUSION

The variation of the lyophilization process and formulation utilizing excipients enabled an optimization of the FPF of the novel lyophilisate based DPI system.

Inhaled Human [rDNA Origin] Insulin, a Novel Formulation for Diabetes Mellitus

Diabetic complications have been reduced significantly with the introduction of insulin more than 8 decades prior. Despite the proven benefits of normal glycemic levels, patients are deterred by the inconvenience and expect worse pain than there is on average with multiple daily insulin injections. Inhaled insulin was approved by the Food and Drug Administration in early 2006 and is a novel product that introduces inhaled insulin as an alternate to the traditional subcutaneous delivery system, and hence could potentially improve patient compliance. The objective of this article is to review the clinical pharmacology, pharmacokinetic and pharmacodynamic properties, clinical efficacy, and tolerability of inhaled insulin.

Ternary interpolyelectrolyte complexes insulin-poly(methylaminophosphazene)-dextran sulfate for oral delivery of insulin

Ternary interpolyelectrolyte complexes of insulin with biodegradable synthetic cationic polymer, poly(methylaminophosphazene) hydrochloride (PMAP), and dextran sulfate (DS) were investigated by means of turbidimetry, dynamic light scattering, phase analysis, and high-sensitivity differential scanning calorimetry. Formation of ternary insoluble stoichiometric Insulin-PMAP-DS complexes was detected under conditions imitating the human gastric environment (pH 2, 0.15 M NaCl). A complete immobilization of insulin in the complexes was observed in a wide range of the reaction mixture compositions. The ternary complexes were shown to dissolve and dissociate under conditions imitating the human intestinal environment (pH 8.3, 0.15 M NaCl). The products of the complex dissociation were free insulin and soluble binary Insulin-PMAP complexes. The conformational stability of insulin in the soluble complexes of various compositions was investigated by high-sensitivity differential scanning calorimetry. The dependence of the excess denaturation free energy of insulin in these complexes on the PMAP content was obtained. The binding constants of the folded and unfolded forms of insulin to the PMAP polycation were estimated. Proteolysis of insulin involved in the insoluble ternary complexes by pepsin was investigated under physiological conditions. It was found that the complexes ensure an almost 100% protection of insulin against proteolytic degradation. The obtained results provide a perspective basis for development of oral insulin preparations.

Time-action profile of an oral enteric insulin formulation in healthy Chinese volunteers

BACKGROUND

Insulin is an essential treatment for both type 1 and 2 diabetes. Among the available routes of insulin administration, oral delivery is the most appealing option.

OBJECTIVE

The purpose of this study was to evaluate the pharmacodynamic and pharmacokinetic profiles of orally administered enteric insulin and compare the time-action of these oral insulin capsules with neutral protamine Hagedorn (NPH) insulin.

METHODS

This was a single-center, randomized, 4-period, crossover study. Twelve healthy volunteers (3 per group) received 1 of 3 doses of oral enteric insulin (50, 100, or 200 U) or 1 subcutaneous injection of NPH insulin (6 U) on 4 separate days. After administration, glucose infusion rates and serum insulin concentrations were monitored for 10 hours.

RESULTS

Glucose infusion rates increased after administration of either NPH or oral enteric insulin. The mean times for maximal metabolic effects for 50, 100, and 200 U of oral enteric insulin were 250 (118), 170 (58), and 236 (132) minutes, respectively, compared with 243 (79) minutes for NPH insulin. The onset of action was slower for oral enteric insulin at 50 U (38 [10] minutes), 100 U (41 [18] minutes), and 200 U (65 [58] minutes) compared with NPH insulin (35 [8] minutes). The maximum glucose infusion rates for oral enteric insulin treatment (1.66 [0.50], 1.61 [1.00], and 1.80 [0.60] mg/kg/min for 50, 100, and 200 U, respectively) were lower compared with NPH insulin (2.06 [0.82] mg/kg/min), although these differences were not statistically significant.

CONCLUSIONS

Oral enteric insulin capsules induced significant glucodynamic effects and exhibited a time-action profile similar to that of NPH insulin in these healthy volunteers. No detectable increases in serum insulin concentration were observed in any treatment group. Trial registry number: ChiCTR-TRC-12001872.