Nasal absorption enhancers for biosynthetic human growth hormone in rats

A breath of fresh air: inhaled antibodies to combat respiratory infectious diseases - a clinical trial overview

INTRODUCTION

With the worldwide growing burden of respiratory tract infections (RTIs), innovative therapeutic approaches are in high demand. Inhaled antibodies (Abs) represent a promising avenue, offering targeted treatment options with potentially better therapeutic index compared to traditional delivery methods.

AREAS COVERED

This comprehensive review summarizes the challenges faced in delivering Abs by (intranasal and pulmonary) inhalation. It outlines the physiological and biological barriers encountered by inhaled drugs, as well as the influence of delivery devices and formulation on the deposition and efficacy of inhaled molecules. Moreover, it provides a detailed overview of the current clinical trial landscape of inhaled anti-RTI Abs, highlighting the progress in the development of inhaled Abs targeting a range of pathogens, such as severe acute respiratory syndrome coronavirus 2 and respiratory syncytial virus. The mechanism of action, therapeutic targets, and clinical outcomes of these novel therapies are detailed.

EXPERT OPINION

Delivery of Abs by inhalation faces several challenges. Addressing these challenges and developing specific approaches to deliver inhaled Abs represent a promising avenue for the development of the next generation of inhaled Abs. By offering targeted, localized therapy with the potential for a better therapeutic index, inhaled Abs could significantly improve outcomes for patients with RTIs.

Extracellular Vesicles from Mesenchymal Stem Cells: Towards Novel Therapeutic Strategies for Neurodegenerative Diseases

Neurodegenerative diseases are fatal disorders of the central nervous system (CNS) which currently lack effective treatments. The application of mesenchymal stem cells (MSCs) represents a new promising approach for treating these incurable disorders. Growing evidence suggest that the therapeutic effects of MSCs are due to the secretion of neurotrophic molecules through extracellular vesicles. The extracellular vesicles produced by MSCs (MSC-EVs) have valuable innate properties deriving from parental cells and could be exploited as cell-free treatments for many neurological diseases. In particular, thanks to their small size, they are able to overcome biological barriers and reach lesion sites inside the CNS. They have a considerable pharmacokinetic and safety profile, avoiding the critical issues related to the fate of cells following transplantation. This review discusses the therapeutic potential of MSC-EVs in the treatment of neurodegenerative diseases, focusing on the strategies to further enhance their beneficial effects such as tracking methods, bioengineering applications, with particular attention to intranasal delivery as a feasible strategy to deliver MSC-EVs directly to the CNS in an effective and minimally invasive way. Current progresses and limiting issues to the extent of the use of MSC-EVs treatment for human neurodegenerative diseases will be also revised.

Intranasal insulin and orexins to treat age-related cognitive decline

The intranasal (IN) administration of neuropeptides, such as insulin and orexins, has been suggested as a treatment strategy for age-related cognitive decline (ARCD). Because dysfunctional neuropeptide signaling is an observed characteristic of ARCD, it has been suggested that IN delivery of insulin and/or orexins may restore endogenous peptide signaling and thereby preserve cognition. IN administration is particularly alluring as it is a relatively non-invasive method that directly targets peptides to the brain. Several laboratories have examined the behavioral effects of IN insulin in young, aged, and cognitively impaired rodents and humans. These studies demonstrated improved performance on various cognitive tasks following IN insulin administration. Fewer laboratories have assessed the effects of IN orexins; however, this peptide also holds promise as an effective treatment for ARCD through the activation of the cholinergic system and/or the reduction of neuroinflammation. Here, we provide a brief overview of the advantages of IN administration and the delivery pathway, then summarize the current literature on IN insulin and orexins. Additional preclinical studies will be useful to ultimately uncover the mechanisms underlying the pro-cognitive effects of IN insulin and orexins, whereas future clinical studies will aid in the determination of the most efficacious dose and dosing paradigm. Eventually, IN insulin and/or orexin administration may be a widely used treatment strategy in the clinic for ARCD.

Formulation and Evaluation of Neuroactive Drug Loaded Chitosan Nanoparticle for Nose to Brain Delivery: In-vitro Characterization and In-vivo Behavior Study

BACKGROUND

The present work was designed to explore the efficacy of neuroactive drug (risperidone) loaded chitosan lipid nanoparticle (RIS-CH-LNPs) to enhance the bioactivity in schizophrenia via the nasal route.

METHODS

The three-factor and three-level formulation by design approach was used for optimization and their effects were observed on (Y1) size in nm, (Y2) % drug loading, and (Y3) % drug release. The optimized formulation RIS-CH-LNPopt was further evaluated for its surface morphology, ex-vivo permeation study, in-vivo behavior study, and stability study. The developed RIS-CH-LNPs showed nanometric size range with high drug loading and prolonged drug release.

RESULTS

The optimized formulation (RIS-CH-LNPopt) has shown the particle size (132.7 nm), drug loading (7.6 %), drug release (80.7 %) and further ex-vivo permeation study showed 2.32 fold enhancement over RIS-SUS(suspension). In-vivo behavior studies showed that RIS-CH-LNPopt is able to show significant greater bioefficacy as compared to RIS-SUS [intranasal (i.n), intravenous (i.v)]. The pharmacokinetic and brain/plasma ratio of developed chitosan nanoparticle was higher at all time-points as compared to RIS-SUS either given by intranasal or intravenous route that proves the direct nose to brain transport pathway of the drug via nasal administration. The developed chitosan nanoparticle increases nose to brain drug delivery as compared to the dispersion of equivalent dose.

CONCLUSION

The findings of this study substantiate the existence of a direct nose-to-brain delivery route for RIS-CH-LNPs.

Advanced formulations for intranasal delivery of biologics

INTRODUCTION

The global biologics market has been ever increasing over the last decades and is predicted to top Euro 350 by 2020. Facing this scenario, the parenteral route of biologics administration as hitherto standard route is inconvenient for the future. Among the alternatives, the intranasal delivery of therapeutic biologicals seems to be most promising but researchers are still facing challenges as indicated by the scarce number of successfully marketed peptide drugs.

AREAS COVERED

This review article is a compilation of current research focusing on achievements in the field of auxiliary agents for biologics delivery. First, the key benefits of the nose as most promising alternative route of drug administration are highlighted. Then, the potential of the different auxiliary agents in preclinical research is in detail discussed. Moreover, the most used permeation enhancing agents, mucolytic agents, mucoadhesive agents, in situ gelling agents and enzyme inhibiting agents in the formulation of nasal drug delivery systems are described. Thus, the overall purpose of this review is to highlight recent achievements in nasal delivery of biologics and to encourage researchers to work in the direction of needle-free nasal administration of biologics.

EXPERT OPINION

The nasal epithelium is a promising route for biologics administration, which is reflected in a number of well-established products on the market treating chronic diseases as well as a large number of clinical trials currently in progress. The nasal route of drug administration might be a chance to improve therapy of biologics however break-through advances, especially for very complex molecules, such as antibodies, are still needed.

Temozolomide loaded nano lipid based chitosan hydrogel for nose to brain delivery: Characterization, nasal absorption, histopathology and cell line study

The present study was designed to develop and optimize Temozolomide nano lipid chitosan hydrogel formulations (TMZNLCHG) to target the brain through nasal route. The formulation was developed using chitosan as a gelling agent and Vit E: gelucire 44/14 blend as lipid. The formulations were evaluated for particle size, encapsulation efficiency (%EE), drug loading (DL), morphology, drug release, nasal diffusion, cell line study, and histopathology study. The particle size, PDI, %EE, %DL, and drug release were found to be 134 nm, 0.177, 88.45% ± 4.45%, 9.12% ± 0.78%, and 84.23% ± 2.78%, respectively. The enhancement ratio was more than two folds higher than TMZCHG formulation (control) suggesting the superiority of chitosan with lipid as permeability enhancer. The microscopic image of lyophilized TMZNLCHGopt displayed the spherical and rough surface morphology. IC50 was found to be 3.34 μg/ml for TMZNLCHGopt and was 160 μg/ml for pure TMZ. Further, No structural damage was observed with TMZNLCHGopt treated nasal mucosa upon histopathological examination. Overall, the present study produces encouraging findings in the formulation of a non-invasive intranasal route for brain targeting as an alternate to other route for TMZ.

Chemical modification of drug molecules as strategy to reduce interactions with mucus

Many drug molecules possess inadequate physical-chemical characteristics that prevent to surpass the viscous mucus layer present in the surface of mucosal tissues. Due to mucus protective role and its fast turnover, these drug molecules end up being removed from the body before being absorbed and, thus, before exerting any physiologic affect. Envisaging a better pharmacokinetics profile, chemical modifications, to render drug a more mucopenetrating character, have been introduced to drug molecules backbone towards more effective therapies. Mucus penetration increases when drug molecules are provided with net-neutral charge, when they are conjugated with mucolytic agents and through modifications that makes them resistant to enzymes present in mucus, with the overall increase of their hydrophilicity and the decrease of their molecular weight. All of these characteristics act as a whole and influence each other so they must be well thought when drug molecules are being designed for mucosal delivery.

Pulmonary Drug Delivery Following Continuous Vibrating Mesh Nebulization and Inspiratory Synchronized Vibrating Mesh Nebulization During Noninvasive Ventilation in Healthy Volunteers

BACKGROUND

A breath-synchronized nebulization option that could potentially improve drug delivery during noninvasive positive pressure ventilation (NIPPV) is currently not available on single-limb circuit bilevel ventilators. The aim of this study was to compare urinary excretion of amikacin following aerosol delivery with a vibrating mesh nebulizer coupled to a single-limb circuit bilevel ventilator, using conventional continuous (Conti-Neb) and experimental inspiratory synchronized (Inspi-Neb) nebulization modes.

MATERIALS AND METHODS

A crossover clinical trial involving 6 noninvasive ventilated healthy volunteers (mean age of 32.3 ± 9.5 y) randomly assigned to both vibrating mesh nebulization modes was conducted: Inspi-Neb delivered aerosol during only the whole inspiratory phase, whereas Conti-Neb delivered aerosol continuously. All subjects inhaled amikacin solution (500 mg/4 mL) during NIPPV using a single-limb bilevel ventilator (inspiratory positive airway pressure: 12 cm H₂O, and expiratory positive airway pressure: 5 cm H₂O). Pulmonary drug delivery of amikacin following both nebulization modes was compared by urinary excretion of drug for 24 hours post-inhalation.

RESULTS

The total daily amount of amikacin excreted in the urine was significantly higher with Inspi-Neb (median: 44.72 mg; interquartile range [IQR]: 40.50-65.13) than with Conti-Neb (median: 40.07 mg; IQR: 31.00-43.73), (p = 0.02). The elimination rate constant of amikacin (indirect measure of the depth of drug penetration into the lungs) was significantly higher with Inspi-Neb (median: 0.137; IQR: 0.113-0.146) than with Conti-Neb (median: 0.116; IQR: 0.105-0.130), (p = 0.02). However, the mean pulmonary drug delivery rate, expressed as the ratio between total daily urinary amount of amikacin and nebulization time, was significantly higher with Conti-Neb (2.03 mg/min) than with Inspi-Neb (1.09 mg/min) (p < 0.01).

CONCLUSIONS

During NIPPV with a single-limb circuit bilevel ventilator, the use of inspiratory synchronized vibrating mesh nebulization may improve pulmonary drug delivery compared with conventional continuous vibrating mesh nebulization.

Evaluation of neuropeptide loaded trimethyl chitosan nanoparticles for nose to brain delivery

Leucine-enkephalin (Leu-Enk) is a neurotransmitter or neuromodulator in pain transmission. Due to non-addictive opioid analgesic activity of this peptide, it might have great potential in pain management. Leu-Enk loaded N-trimethyl chitosan (TMC) nanoparticles were prepared and evaluated as a brain delivery vehicle via nasal route. TMC biopolymer was synthesized and analyzed by (1)H NMR spectroscopy. TMC nanoparticles were prepared by ionic gelation method. Mean peptide encapsulation efficiency and loading capacity were 78.28±3.8% and 14±1.3%, respectively. Mean particle size, polydispersity index and zeta potential were found to be 443±23 nm, 0.317±0.17 and +15±2 mV respectively for optimized formulations. Apparent permeability coefficient (Papp) of Leu-Enk released from nanoparticles across the porcine nasal mucosa was determined to be 7.45±0.30×10(-6) cm s(-1). Permeability of Leu-Enk released from nanoparticles was 35 fold improved from the nasal mucosa as compared to Leu-Enk solution. Fluorescent microscopy of brain sections of mice showed higher accumulation of fluorescent marker NBD-F labelled Leu-Enk, when administered nasally by TMC nanoparticles, while low brain uptake of marker solution was observed. Furthermore, enhancement in brain uptake resulted into significant improvement in the observed antinociceptive effect of Leu-Enk as evidenced by hot plate and acetic acid induced writhing assay.

Strategies for enhanced peptide and protein delivery

Recent advances in the fields of molecular biology and biotechnology have allowed for the large-scale production and subsequent exploitation of the therapeutic potential of protein- and peptide-based drugs. The facilitation of delivery of this class of drugs must be tailored to meet the requirements and often the limitations dictated by the route of delivery chosen. The aim of this review is to comprehensively discuss several routes of drug delivery, detailing the uses and exploitation of each, from origins to present day approaches. Specific reference is made to the compatibility or incompatibility of each approach in the facilitation of the delivery of drugs of protein origin. Additionally, the physiological nature of the delivery route and the inherent physiological obstacles that must be considered when determining the most suitable approach to drug design and delivery enhancement are also addressed. Examples of novel protein-based drug designs and delivery methodologies that illustrate such enhancement strategies are explored.

Safety Assessment of Trimoniums as Used in Cosmetics

Quaternary ammonium salts, including alkyl chain, alkanol, and polymer derivatives (trimoniums) are used in cosmetics mainly as surfactant-cleansing agents, hair-conditioning agents, and antistatic agents.  The Cosmetic Ingredient Review Expert Panel reviewed the relevant animal and human data and noted gaps in the available safety data for some of the trimomiums.  The available data on many of the trimoniums are sufficient, however, and similar structural activity relationships, functions in cosmetics, and cosmetic product usage supported extending these data to the entire group.  These ingredients were determined to be safe in the present practices of use and concentration when formulated to be nonirritating.

CriticalSorb: a novel efficient nasal delivery system for human growth hormone based on Solutol HS15

The absorption enhancing efficiency of CriticalSorb for human growth hormone (MW 22 kDa) was investigated in the conscious rat model. The principle absorption enhancing component of CriticalSorb, Solutol HS15, comprises polyglycol mono- and di-esters of 12-hydroxystearic acid combined with free polyethylene glycol. When administering hGH nasally in rats with increasing concentrations of Solutol HS15, it was found that for a 10%w/v solution formulation a bioavailability of 49% was obtained in the first 2h after administration. Furthermore it was shown that the most effective ratio of Solutol HS15 to hGH was 4:1 on a mg to mg basis. Histopathology studies in rats after 5 days repeated nasal administration showed that Solutol HS15 had no toxic effect on the nasal mucosa. These results have been confirmed in a 6 month repeat nasal toxicity study in rats. It can be concluded that the principle absorption enhancing component of CriticalSorb - Solutol HS15 - is a potent and non- toxic nasal absorption enhancer that warrants further development.

Thiolated chitosan nanoparticles for the nasal administration of leuprolide: bioavailability and pharmacokinetic characterization

The purpose of this study was to develop thiolated nanoparticles to enhance the bioavailability for the nasal application of leuprolide. Thiolated chitosan-thioglycolic acid (chitosan-TGA) and unmodified chitosan nanoparticles (NPs) were developed via ionic gelation with tripolyphosphate (TPP). Leuprolide was incorporated during the formulation process of NPs. The thiolated (chitosan-TGA) NPs had a mean size of 252 ± 82 nm, a zeta potential of +10.9 ± 4 mV, and payload of leuprolide was 12 ± 2.8. Sustained release of leuprolide from thiolated NPs was demonstrated over 6h, which might be attributed to inter- and/or intramolecular disulfide formation within the NPs network. Ciliary beat frequency (CBF) study demonstrated that thiolated NPs can be considered as suitable additives for nasal drug delivery systems. Compared to leuprolide solution, unmodified NPs and thiolated NPs provoked increased leuprolide transport through porcine nasal mucosa by 2.0 and 5.2 folds, respectively. The results of a pharmacokinetic study in male Sprague-Dawley rats showed improved transport of leuprolide from thiolated NPs as compared to leuprolide solution. Thiolated NPs had a 6.9-fold increase in area under the curve, more than 4-fold increase in elimination half-life, and a ∼3.8-fold increase in maximum plasma concentration compared to nasal solution alone. The relative nasal bioavailability (versus s.c. injection) of leuprolide thiolated NPs calculated on the basis of AUC((0-6)) was about 19.6% as compared to leuprolide solution 2.8%. The enhanced bioavailability of leuprolide is likely due to facilitated transport by thiolated NPs rather than improved release.

Mucoadhesive microspheres for nasal administration of an antiemetic drug, metoclopramide: in-vitro/ex-vivo studies

Microparticulate delivery systems designed for the nasal administration of an antiemetic drug, metoclopramide hydrochloride, were prepared. Microspheres composed of sodium alginate, chitosan hydrochloride, or both, were obtained using a spray-drying method; some batches of drug-free microparticles were prepared as a comparison. The morphology, in-vitro swelling behaviour, mucoadhesive properties and drug release from microparticles were evaluated. Ex-vivo drug permeation tests were carried out using sheep nasal mucosa; permeation test of the drug solution was peformed as comparison. During ex-vivo permeation tests, transmission electron microscopy (TEM) analyses were carried out on the nasal mucosa to study the morphological changes of epithelial cells and tight junctions, while the change in microsphere morphology was examined using photostereo microscopy (PM). Spray-dried microparticles had a mean diameter (dvs) in the range of about 3–10 μm. They showed good in-vitro mucoadhesive properties. In-vitro release profiles and swelling behaviour depended on their composition: the drug release occurred in 1–3 h. Ex-vivo studies showed that drug permeation through the mucosa from microparticles based on chitosan was higher than from those consisting of alginate alone. This can be related to the penetration enhancing properties of chitosan. Complexation of chitosan with alginate led to a control of the drug release. Microscopy observation of microspheres during the permeation tests revealed that microparticles swelled and gelled, maintaining their shape. TEM analyses of the mucosa after exposure to the microparticles consisting of alginate/chitosan showed opened tight junctions. This preliminary study shows that alginate/chitosan spray-dried microspheres have promising properties for use as mucoadhesive nasal carriers of an antiemetic drug.

Intranasal delivery: physicochemical and therapeutic aspects

Interest in intranasal (IN) administration as a non-invasive route for drug delivery continues to grow rapidly. The nasal mucosa offers numerous benefits as a target issue for drug delivery, such as a large surface area for delivery, rapid drug onset, potential for central nervous system delivery, and no first-pass metabolism. A wide variety of therapeutic compounds can be delivered IN, including relatively large molecules such as peptides and proteins, particularly in the presence of permeation enhancers. The current review provides an in-depth discussion of therapeutic aspects of IN delivery including consideration of the intended indication, regimen, and patient population, as well as physicochemical properties of the drug itself. Case examples are provided to illustrate the utility of IN dosing. It is anticipated that the present review will prove useful for formulation scientists considering IN delivery as a delivery route.

Advances in nasal drug delivery through tight junction technology

New approaches for enhancing intranasal drug delivery based on recent discoveries on the molecular biology of tight junctions (TJ) are significantly improving the bioavailability of 'non-Lipinsky' small molecules, and peptide, protein and oligonucleotide drugs. As knowledge of the structure and function of the TJ has developed, so has the ability to identify mechanism-based TJ modulators using high-throughput molecular biology-based screening methods. The present review focuses on recent developments on the TJ protein complex as a lipid raft-like membrane microdomain, the emerging role of unique endocytic pathways in regulating TJ dynamics, and the utility of techniques such as RNA interference and phage display to study TJ components and identify novel peptides and related molecules that can modulate their function. Experimental and statistical methodologies used for the identification of new classes of TJ modulators are described, which are capable of reversibly opening TJ barriers with broad potential to significantly improve intranasal and, eventually, oral drug delivery. The development of an advanced intranasal formulation for the obesity therapeutic PYY(3-36), the endogenous Y2 receptor agonist is also reviewed.

Improved nasal absorption of salmon calcitonin by powdery formulation with N-acetyl-L-cysteine as a mucolytic agent

To establish a new formulation technology for the nasal delivery of peptide and protein drugs, we examined whether a mucolytic agent, N-acetyl-L-cysteine (NAC), could enhance the nasal absorption of a powder form of salmon calcitonin, a model peptide drug. We used ethylcellulose as an inert water-insoluble excipient. Various test formulations were prepared, and the effects on nasal absorbability were evaluated in rats and dogs. The powder formulation with NAC gave significant nasal absorption of SCT in both animal models, with absolute bioavailabilities of 30.0% in rats and 24.9% in dogs. Also, nasal administration of this formulation gave a quicker absorption rate than subcutaneous administration of SCT. NAC may reduce nasal fluid viscocity and improve accessibility of the drug to the epithelial membrane. The powder SCT/NAC/ethylcellulose formulation did not induce irritation or histological damage to the nasal membrane in rabbits. These results suggest that this formulation technology may be widely applicable for the nasal delivery of peptide or protein drugs.

Analgesic effects of intra-nasal enkephalins

The analgesic effects of intranasal delivery of leucine enkephalin (Leu-Enk) and its synthetic analogue [D-ala(2)]-leucine enkephalinamide (YAGFL) with or without enzyme inhibitors and/or absorption enhancers were investigated using the acetic acid-induced writhing test in mice. The analgesic activity was significantly affected by the time delay after the administration of Leu-Enk; the inhibition rates for the groups administered with acetic acid 5 min and 30 min after the administration of Leu-Enk were 56.40 +/- 8.54 and 17.98 +/- 7.07%, respectively. The addition of enzyme inhibitors and absorption enhancers markedly increased the inhibition rate of Leu-Enk and YAGFL; their inhibition rates were about four times and twice those without any enzyme inhibitor or absorption enhancer, respectively. The enzyme inhibitors and absorption enhancers that produced the highest inhibition rates of Leu-Enk and YAGFL were azelaic acid (1%), thimerosal (0.5 mM, TM), ethylenediamine-tetraacetic acid (5 mM, EDTA) and L-alpha-lysophosphatidylcholine (0.5%, LPC), and TM (0.5 mM), EDTA (5 mM), LPC (0.5%) and povidone (5%), respectively. The ED50 value of both enkephalins was also determined and found to be about 13 microg kg(-1), which is 850 and 60 times more potent than literature values for ketoprofen and morphine, respectively. Based on these results it was concluded that Leu-Enk or YAGFL could exert very high analgesic activity when administered nasally with a combination of inhibitors and absorption enhancers as compared with other analgesics.

Thiolated chitosan microparticles: a vehicle for nasal peptide drug delivery

The goal of this study was to develop a microparticulate delivery system based on a thiolated chitosan conjugate for the nasal application of peptides. Insulin was used as model peptide. For thiolation of chitosan 2-iminothiolane was covalently linked to chitosan. The resulting chitosan-TBA (chitosan-4-thiobutylamidine) conjugate featured 304.89+/-63.45 micromol thiol groups per gram polymer. 6.5% of these thiol groups were oxidised. A mixture of the chitosan-TBA conjugate, insulin and the permeation mediator reduced glutathione were formulated to microparticles. Control microparticles comprised unmodified chitosan and insulin. As second control served mannitol-insulin microparticles. All microparticulate systems were prepared via the emulsification solvent evaporation technique. In 100 mM phosphate buffer pH 6.8 chitosan-TBA-insulin microparticles swelled 4.39+/-0.52-fold in size, whereas chitosan based microparticles did not swell at all. Chitosan-TBA microparticles showed a controlled release of fluorescein isothiocyanate (FITC)-labelled insulin over 6 h. Nasal administered chitosan-TBA-insulin microparticles led to an absolute bioavailability of 7.24+/-0.76% (means+/-S.D.; n=3) in conscious rats. In contrast, chitosan-insulin microparticles and mannitol-insulin microparticles exhibited an absolute bioavailability of 2.04+/-1.33% and 1.04+/-0.27%, respectively (means+/-S.D.; n=4). Because of these results microparticles comprising chitosan-TBA and reduced glutathione seem to represent a useful formulation for the nasal administration of peptides.

Enhancement of nasal absorption of large molecular weight compounds by combination of mucolytic agent and nonionic surfactant

For improving the nasal absorption of poorly absorbable hydrophilic compounds, the suitability of a combination of a mucolytic agent, N-acetyl-L-cysteine (NAC), and a nonionic surfactant, polyoxyethylene (C25) lauryl ether (laureth-25), was examined. Rat studies with fluorescent isothiocyanate-labeled dextran (molecular weight ca. 4.4 kDa, FD-4) as a model hydrophilic compound revealed dramatic enhancement of nasal absorption when NAC and laureth-25 were simultaneously applied. The nasal bioavailability of FD-4 in saline solution was 8.2+/-0.6% but increased to 40.0+/-5.5% when 5% NAC and 5% laureth-25 were added. This synergistic enhancement could result from the mucolytic activity of NAC in reducing mucous viscosity by which the accessibilities of FD-4 and laureth-25 to the epithelial membrane were increased. Further rat studies proved that this formulation increased nasal absorption of salmon calcitonin. Absolute bioavailability from saline solution containing 5% NAC and 1% laureth-25 was 26.8+/-2.2%, 3.5 times that of the commercial calcitonin nasal spray Miacalcin (7.7+/-2.1%). The potential of the new formulation to cause tissue damage in terms of hemolytic activity and liberation of phospholipid from the nasal membranes was nil or slight. The combination of NAC and laureth-25 appears suitable for use in development of nasal products for poorly absorbable drugs, especially peptide and protein drugs.

Inhibition of appetite by nasal leptin administration in rats

OBJECTIVE

Leptin inhibits appetite and reduces body weight. However, subcutaneous leptin administration is not very effective on weight reduction. The present studies were undertaken to test the hypotheses that nasally administered leptin effectively accesses to the brain and inhibits appetite.

METHODS

Recombinant leptin (0.5 mg/rat) was administered into the bilateral nasal spaces of rats (i.n.). Changes in serum immunoreactive leptin (IRL) and cerebrospinal fluid (CSF)-IRL concentrations after i.n. leptin administration were compared after intraperitoneal (i.p.) administration. The influence of 0.1 or 0.5% lysophosphatidylcholine (LPC) as an optimizer of leptin absorption was examined. The anorexic effects of i.n. leptin were compared with i.p. leptin in ad libitum fed rats.

RESULTS

The i.n. leptin increased CSF-IRL concentrations, although serum IRL concentrations of rats administered leptin i.n. were lower than those administered i.p. The addition of 0.1 and 0.5% LPC dose-dependently increased serum IRL concentrations, but did not modify CSF-IRL concentrations in i.n. leptin-treated rats. The i.n. leptin inhibited dark-time food consumption at 0-1 h and 3-6 h in ad libitum fed rats. In contrast, i.p. leptin reduced food consumption only for an hour. Phosphorylated signal transducer and activator of transcription (STAT) 3 immunoreactive cells increased in the arcuate nucleus (ARC) of the hypothalamus at 3 h only following i.n. leptin.

CONCLUSION

The present study demonstrated that i.n. leptin caused longer inhibition of appetite and phosphorylation of STAT3 in ARC. It is concluded that the trans-nasal route may be useful for the selective access of leptin to the brain in obese people.

Thiomers in noninvasive polypeptide delivery: in vitro and in vivo characterization of a polycarbophil-cysteine/glutathione gel formulation for human growth hormone

This study was aimed at investigating the potential of a new polycarbophil-cysteine (PCP-Cys)/glutathione (GSH) gel formulation to enhance the permeation of the model drug human growth hormone (hGH) across nasal mucosa in vitro and in vivo. The aqueous nasal gel contained PCP-Cys, GSH, and hGH in a final concentration of 0.3%, 0.5%, and 0.6% (m/v), respectively. In vitro permeation studies were performed in Ussing chambers on freshly excised bovine nasal mucosa using fluorescence-labeled dextran (molecular mass: 4.3 kDa; FD-4) and hGH (FITC-hGH). The release profile of FITC-hGH from the gel formulation and an unmodified PCP control formulation was determined. Furthermore, in vivo studies in rats were performed comparing the PCP-Cys/GSH/hGH gel with PCP/hGH control gel and physiological saline. The permeation of FD-4 and FITC-hGH across the nasal mucosa was improved two-fold and three-fold, respectively, in the presence of PCP-Cys/GSH. The PCP-Cys/GSH/hGH gel and the PCP/hGH control gel showed the same biphasic and matrix-controlled drug release. The nasal administration of the PCP-Cys/GSH/hGH gel formulation to rats resulted in a significantly increased and prolonged hGH plasma concentration-time profile versus unmodified PCP gel and physiological saline. According to these results, PCP-Cys gels might represent a promising new strategy for systemic nasal polypeptide delivery.

Absorption enhancers for nasal drug delivery

This paper describes the basic concepts for the transmucosal delivery of drugs, and in particular the use of the nasal route for delivery of challenging drugs such as polar low-molecular-weight drugs and peptides and proteins. Strategies for the exploitation of absorption enhancers for the improvement of nasal delivery are discussed, including consideration of mechanisms of action and the correlation between toxic effect and absorption enhancement. Selected enhancer systems, such as cyclodextrins, phospholipids, bioadhesive powder systems and chitosan, are discussed in detail. Examples of the use of these enhancers in preclinical and clinical studies are given. Methods for assessing irritancy and damage to the nasal membrane from the use of absorption enhancers are also described. Finally, the mucosal use of absorption enhancers (chitosan) for the improved nasal delivery of vaccines is reported with reference to recent phase I/II clinical studies.

Permeability issues in nasal drug delivery

The nasal route is one of the most permeable and highly vascularized site for drug administration ensuring rapid absorption and onset of therapeutic action. It has been potentially explored as an alternative route for drugs with poor bioavailability and for the delivery of biosensitive and high molecular weight (MW) compounds such as proteins, peptides, steroids, vaccines, and so on. This review discusses the major factors affecting the permeability of drugs or biomolecules through the nasal mucosa, including biological, formulation and device-related factors. This information could potentially help to achieve desired plasma concentrations of drugs without compromising or altering the normal physiology of the nasal cavity.

The biopharmaceutical aspects of nasal mucoadhesive drug delivery

Nasal drug administration has frequently been proposed as the most feasible alternative to parenteral injections. This is due to the high permeability of the nasal epithelium, allowing a higher molecular mass cut-off at approximately 1000 Da, and the rapid drug absorption rate with plasma drug profiles sometimes almost identical to those from intravenous injections. Despite the potential of nasal drug delivery, it has a number of limitations. In this review, the anatomy and physiology of the nasal cavity, as well as ciliary beating and mucociliary clearance as they relate to nasal drug absorption, are introduced. The rationale for nasal drug delivery and its limitations, some factors that influence nasal drug absorption, and the experimental models used in nasal drug delivery research are also reviewed. Nasal mucoadhesion as a promising method of nasal absorption enhancement is discussed, and factors that influence mucoadhesion, as well as safety of nasal mucoadhesive drug delivery systems are reviewed in detail. Nasal drug administration is presently mostly used for local therapies within the nasal cavity. Anti-allergic drugs and nasal decongestants are the most common examples. However, nasal drug administration for systemic effects has been practised since ancient times. Nasally-administered psychotropic drugs by native Americans, the use of tobacco snuffs, and nasal administration of illicit drugs such as cocaine are all well known (Illum & Davis 1992). Nowadays, the nasal cavity is being actively explored for systemic administration of other therapeutic agents, particularly peptides and proteins (Illum 1992; Edman & Björk 1992), as well as for immunization purposes (Lemoine et al 1998). To better understand the basis for nasal drug absorption and factors that can influence it, a brief review of the anatomy and physiology of the nose is appropriate.

Intranasal insulin delivery and therapy

Intranasal insulin delivery has been widely investigated as an alternative to subcutaneous injection for the treatment of diabetes. The pharmacokinetic profile of intranasal insulin is similar to that obtained by intravenous injection and, in contrast to subcutaneous insulin delivery, bears close resemblance to the 'pulsatile' pattern of endogenous insulin secretion during meal-times. The literature suggests that intranasal insulin therapy has considerable potential for controlling post-prandial hyperglycaemia in the treatment of both IDDM and NIDDM. However, effective insulin absorption via the nasal route is unlikely without employing the help of absorption enhancers or promoters which are able to modulate nasal epithelial permeability to insulin and/or prolong the residence time of the drug formulation in the nasal cavity. This article discusses the structure and function of the nasal cavity, the barriers which prevent nasal insulin absorption and through the use of absorption enhancers or promoters methods by which these barriers may be overcome.

Intranasal absorption of granulocyte-colony stimulating factor (G-CSF) from powder formulations, in sheep

Granulocyte-colony stimulating factor (G-CSF) was administered to sheep in three different nasal formulations and as a subcutaneous injection. The nasal formulations were: a solution containing L-alpha-lysophosphatidylglycerol (LPG), a powder formulation comprising small starch microspheres (SSMS) and a powder formulation comprising SSMS and LPG. Absorption of G-CSF was assessed directly by quantitation in plasma and indirectly by measurement of the pharmacodynamic response in terms of leucocyte and neutrophil counts. After the nasal delivery of the G-CSF powder formulation containing SSMS and LPG the absorption of G-CSF was significantly higher (P<0.01) than that from the simple nasal solution or the powder without the enhancer, but the resulting pharmacological response was not significantly different. The bioavailability of G-CSF from the powder formulation containing SSMS and LPG relative to the subcutaneous injection was 8.4% (+/-3.4). We also found that at the respective G-CSF doses investigated, the pharmacodynamic response of this nasal formulation, was similar to that obtained after the subcutaneous administration. The study indicates that the powder formulation containing enhancers could offer an alternative delivery route for G-CSF in the form of intranasal administration.

Presystemic bradykinin metabolism in sheep and rat nasal homogenates

Bradykinin (BK) and its fragments BK(1-8), BK(1-7), and BK(1-5) were incubated with sheep nasal homogenates to investigate the extent of peptide metabolism within the nasal mucosa. The products for both bradykinin and BK(1-8) degradation were found to be BK(1-7) and BK(1-5). BK(1-7) was metabolized to BK(1-5) alone. The patterns of degradation suggest that the Pro7-Phe8 bond of bradykinin was hydrolyzed first, then BK(1-7) was further hydrolyzed to form BK(1-5). The metabolism of bradykinin in rat nasal homogenates and plasma was also investigated. BK(1-5) was the only metabolite measurable in the rat nasal homogenates, likely due to the activity of an endopeptidase. The reduction in the bradykinin degradation rate resulting from the inhibition of angiotensin converting enzyme (ACE) or carboxypeptidase N indicates that these enzymes participate in mucosal bradykinin metabolism to some degree. In comparison, the products of bradykinin hydrolysis in rat plasma were found to be BK(1-8), BK(1-7), and BK(1-5). These results indicate that the enzyme populations or/and activities vary significantly between different species and between different tissues within the same species. Although significant aminopeptidase activities were detected in the sheep nasal homogenates, bradykinin was not affected by their presence, since the N-terminal sequence of bradykinin is not susceptible to hydrolysis by most aminopeptidases.

Development of a human nasal epithelial cell culture model and its suitability for transport and metabolism studies under in vitro conditions

A human nasal epithelial cell culture model has been adapted to observe transport and metabolism of drugs, e.g., peptides. Human nasal epithelial cells, isolated by protease treatment of human nasal conchae, grew to confluency after 6-8 days using DMEM supplemented with 1% nonessential amino acids, 1% glutamine, 10% FCS and 1% antibiotics. These cultures expressed microvilli and actively beating cilia as documented by light microscopy and scanning electron microscopy (SEM). Tight junctions were confirmed by dome formation and positive actin staining using FITC-labelled phalloidin. Preliminary transport studies, carried out with FITC-labelled Dextran (FD 4, MW 4400) and Sulforhodamine (SR 101, MW 607), demonstrated the intact barrier function of the cultured monolayer, grown on filter membranes. In addition, the cultured cells metabolized Leu-Enkephalin to Des-Tyr-Leu-Enkephalin demonstrating the presence of aminopeptidase, a naturally occurring enzyme in the human nasal mucosa.

Nasal Delivery of Atenolol and Timolol in the Rat and the Effect of Absorption Enhancers

This study has investigated the nasal mucosa as an alternative site for the administration of atenolol and timolol maleate, two antihypertensive agents whose oral administration is subject to either incomplete absorption (atenolol) or significant first-pass effect (timolol). To this end, the intranasal absorption of these drugs was first evaluated in an in vivo rat model, with and without the absorption enhancers amastatin and sodium glycocholate, and next compared with those obtained after oral and intravenous dosings. Use of the intranasal route resulted in higher plasma drug levels than by the oral route (p < 0.05) and in systemic bioavailabilities that compared very favorably with those obtained intravenously (ca. 90% for both drugs). Bioavailability of the title drugs from the nasal mucosa improved upon coadministration with an absorption enhancer (96-98%, atenolol; ca. 99%, timolol).

Nasal absorption of growth hormone in normal subjects: studies with four different formulations

OBJECTIVE

Current growth hormone (GH) therapy with daily subcutaneous injections results in elevated serum concentrations of GH lasting for several hours, whereas physiologic GH secretion is characterized by a short-duration peak and low basal concentrations. A closer imitation of this pattern might be achieved by administering GH nasally. We studied the effect on the absorption of nasally administered human GH of increasing concentrations of the enhancer didecanoyl-L-alpha-phosphatidylcholine (DDPC).

DESIGN

Four formulations of nasal GH containing the enhancer DDPC in the relative concentrations 0, 4, 8, and 16% w/w were administered in random order.

SETTING

Participants were admitted to the hospital during the four study periods.

INTERVENTIONS

On four occasions the subjects received GH 6 IU (2 mg) in each nostril. Blood was sampled frequently for four hours. Anterior rhinoscopy was performed at 0 and 4 h. During the study the subjects completed a questionnaire to record nasal symptoms.

PATIENTS

Sixteen healthy subjects were examined at 0800 h after an overnight fast.

MAIN OUTCOME MEASURES

Bioavailability of a nasal preparation of human GH: area under the curve (AUC), the maximum concentration (Cmax), and the time to reach maximum concentration (tmax). Scores for each nasal symptom were recorded as were the total scores.

RESULTS

AUC, Cmax, and tmax were not significantly affected by increasing the DDPC concentration from 0 to 4 percent or from 8 to 16 percent. AUC and Cmax, however, increased significantly when the concentration of DDPC was changed from 4 to 8 percent. Mean (+/- SD) AUC (microgram.h/L) increased from 20.51 +/- 10.53 (4 percent) to 46.14 +/- 34.59 (8 percent), (p < 0.005). Mean (+/- SD) of Cmax (microgram/L) increased from 11.11 +/- 5.02 (4 percent) to 28.22 +/- 20.85 (8 percent), (p = 0.002). Mean (+/- SD) of tmax (min) was not significantly different on the four occasions (range 40.6 +/- 36.4 to 61.0 +/- 45.2 min, p = 0.13). The symptom scores (range 17.56-21.5, maximum 360) were not significantly different (p = 0.59).

CONCLUSIONS

Increasing the relative concentration of the enhancer DDPC increases the absorption of nasally administered GH.

Lack of effect of ammonium glycyrrhizinate on the morphology of ovine nasal mucosa in vitro

Glycyrrhetinic acid derivatives are reported to be nasal absorption promoters (1). Effects of ammonium glycyrrhizinate (AMGZ) on the in vitro morphology of ovine nasal mucosa were therefore examined by light and electron microscopy. Nasal mucosa was stripped from the submucosa and mounted in Ussing chambers. Exposure of the apical surface to 2% ammonium glycyrrhizinate (24 mM) for 90 min caused no histopathological changes to the nasal epithelium. Epithelial integrity remained intact as evidenced by the continued presence of morphologically intact junctional complexes. No sloughing of the epithelial layer from the basement membrane was observed, and cilia and microvilli were not affected by treatment with AMGZ. The results indicate that short-term exposure in vitro to ammonium glycyrrhizinate caused no overt morphological damage to ovine nasal mucosa.

Mechanism and site dependency of intestinal mucosal transport and metabolism of thymidine analogues

This study has been undertaken to investigate the mechanisms of intestinal mucosal transport and metabolism of thymidine analogues and to identify any optimal site(s) of the rat intestine particularly involved in the absorption of thymidine analogues. The intestinal absorption of 3'-azido-3'-deoxythymidine (AZT) was studied at three initial concentrations in four segments of the rat intestine using an in situ recirculating perfusion technique. Disappearance of AZT followed first-order kinetics throughout the gastrointestinal (GI) tract at all tested concentrations. The apparent first-order rate constants were found to be relatively invariant over a broad range of concentrations from 0.01 to 1.0 mM. Corrected for the length of each segment, the apparent permeability (Papp) of AZT was 3.01 +/- 0.32 x 10(-5) cm/sec (mean +/- SE) in the duodenum, 2.06 +/- 0.24 x 10(-5) cm/sec in the upper jejunum, 0.76 +/- 0.13 x 10(-5) cm/sec in the combined lower jejunum and ileum, and 0.32 +/- 0.10 x 10(-5) cm/sec in the colon, which indicated that intrinsic absorptivity was greater in the upper GI tract than in the lower portions possibly due to the differences in surface area for absorption. No AZT metabolite appeared in any part of the GI tract. On the other hand, thymidine and other analogues, i.e., 5-iodo-2'-deoxyuridine and 2'-deoxyuridine, were rapidly metabolized into nucleobase and sugar in the upper GI tract, whereas in the colon no metabolite appeared. A free 3'-OH group appears to be necessary for the metabolism (catabolism) of thymidine analogues in the rat intestine mainly by pyrimidine nucleoside phosphorylase.(ABSTRACT TRUNCATED AT 250 WORDS)

Drug metabolism in the nasal mucosa

Nasal delivery is a potential alternative for systemic availability of drugs restricted to intravenous administration, such as peptide and protein drugs. Although nasal delivery avoids the hepatic first-pass effect, the enzymatic barrier of the nasal mucosa creates a pseudo-first-pass effect. The xenobiotic metabolic activity in the nasal epithelium has been investigated in several species including humans. The Phase I, cytochrome P-450 enzymes have been studied extensively for their toxicological significance, since these enzymes metabolize inhaled pollutants into reactive metabolites which may induce nasal tumors. The cytochrome P-450 activity in the olfactory region of the nasal epithelium is higher even than in the liver, mainly because of a three- to fourfold higher NADPH-cytochrome P-450 reductase content. Phase II activity has also been found in the nasal epithelium. The delivery of peptides and proteins has been hindered by the peptidase and protease activity in the nasal mucosa. The predominant enzyme appears to be aminopeptidase among other exopeptidases and endopeptidases. The absorption of peptide drugs can be improved by using aminoboronic acid derivatives, amastatin, and other enzyme inhibitors as absorption enhancers. It is possible that some of the surfactants, e.g., bile salts, increase absorption by inhibiting the proteolytic enzymes. Thus, in addition to the permeation barriers, there also exists an enzymatic barrier to nasal drug delivery, which is created by metabolic enzymes in the nasal epithelium.