Effects of absorption enhancers on rat nasal epithelium in vivo: release of marker compounds in the nasal cavity

Enhanced brain distribution of Ginsenoside F1 via intranasal administration in combination with absorption enhancers

Ginsenoside F1 (GF1) is a potential drug candidate for the treatment of Alzheimer's disease. Nevertheless, its low oral bioavailability and poor solubility limit clinical application. By utilizing either a direct or indirect approach, intranasal administration is a non-invasive drug delivery method that can deliver drugs to the brain rapidly. But large molecule drug delivered to the brain through intranasal administration may be insufficient to reach required concentration for therapeutic effect. In this study, using GF1 as a model drug, the feasibility of intranasal administration in combination with absorption enhancers to increase brain distribution of GF1 was explored. First of all, the appropriate absorption enhancers were screened by in situ nasal perfusion study. GF1-HP-β-CD inclusion complex was prepared and characterized. Thereafter, in vivo absorption of GF1 after intranasal or intravenous administration of its inclusion complex with/without absorption enhancers was investigated, and safety of the formulations was evaluated. The results showed that 2% Solutol HS 15 was a superior absorption enhancer. HP-β-CD inclusion complex improved GF1 solubility by 150 fold. Following intranasal delivery, the absolute bioavailability of inclusion complex was 46%, with drug brain targeting index (DTI) 247% and nose-to-brain direct transport percentage (DTP) 58%. Upon further addition of 2% Solutol HS 15, the absolute bioavailability was increased to 75%, with DTI 315% and DTP 66%. Both nasal cilia movement and biochemical substances (total protein and lactate dehydrogenase) leaching studies demonstrated 2% Solutol HS 15 was safe to the nasal mucosa. In conclusion, intranasal administration combining with safe absorption enhancers is an effective strategy to enhance drug distribution in the brain, showing promise for treating disorders related to the central nervous system.

Fabricating Polymer/Surfactant/Cyclodextrin Hybrid Particles for Possible Nose-to-Brain Delivery of Ropinirole Hydrochloride: In Vitro and Ex Vivo Evaluation

Ropinirole is a non-ergolinic dopamine agonist used to manage Parkinson's disease and it is characterized by poor oral bioavailability. This study aimed to design and develop advanced drug delivery systems composed of poloxamer 407, a non-ionic surfactant (Tween 80), and cyclodextrins (methyl-β-CD or hydroxy-propyl-β-CD) for possible brain targeting of ropinirole after nasal administration for the treatment of Parkinson's disease. The hybrid systems were formed by the thin-film hydration method, followed by an extensive physicochemical and morphological characterization. The in vitro cytotoxicity of the systems on HEK293 cell lines was also tested. In vitro release and ex vivo mucosal permeation of ropinirole were assessed using Franz cells at 34 °C and with phosphate buffer solution at pH 5.6 in the donor compartment, simulating the conditions of the nasal cavity. The results indicated that the diffusion-controlled drug release exhibited a progressive increase throughout the experiment, while a proof-of-concept experiment on ex vivo permeation through rabbit nasal mucosa revealed a better performance of the prepared hybrid systems in comparison to ropinirole solution. The encouraging results in drug release and mucosal permeation indicate that these hybrid systems can serve as attractive platforms for effective and targeted nose-to-brain delivery of ropinirole with a possible application in Parkinson's disease. Further ex vivo and in vivo studies to support the results of the present work are ongoing.

Targeted Delivery of Erythropoietin Hybridized with Magnetic Nanocarriers for the Treatment of Central Nervous System Injury: A Literature Review

Although the incidence of central nervous system injuries has continued to rise, no promising treatments have been elucidated. Erythropoietin plays an important role in neuroprotection and neuroregeneration as well as in erythropoiesis. Moreover, the current worldwide use of erythropoietin in the treatment of hematologic diseases allows for its ready application in patients with central nervous system injuries. However, erythropoietin has a very short therapeutic time window (within 6–8 hours) after injury, and it has both hematopoietic and nonhematopoietic receptors, which exhibit heterogenic and phylogenetic differences. These differences lead to limited amounts of erythropoietin binding to in situ erythropoietin receptors. The lack of high-quality evidence for clinical use and the promising results of in vitro/in vivo models necessitate fast targeted delivery agents such as nanocarriers. Among current nanocarriers, noncovalent polymer-entrapping or polymer-adsorbing erythropoietin obtained by nanospray drying may be the most promising. With the incorporation of magnetic nanocarriers into an erythropoietin polymer, spatiotemporal external magnetic navigation is another area of great interest for targeted delivery within the therapeutic time window. Intravenous administration is the most readily used route. Manufactured erythropoietin nanocarriers should be clearly characterized using bioengineering analyses of the in vivo size distribution and the quality of entrapment or adsorption. Further preclinical trials are required to increase the therapeutic bioavailability (in vivo biological identity alteration, passage through the lung capillaries or the blood brain barrier, and timely degradation followed by removal of the nanocarriers from the body) and decrease the adverse effects (hematological complications, neurotoxicity, and cytotoxicity), especially of the nanocarrier.

Strategies to facilitate or block nose-to-brain drug delivery

Nose-to-brain delivery has gained significant interest over the past several decades. This has resulted in numerous strategies described to improve the delivery of drugs to the brain directly through the olfactory epithelium of the nasal cavity. In some cases, intranasal administration may be more effective than other routes of administration in treating central nervous system and related disorders. Here, we briefly review the strategies that have been used to facilitate nose-to-brain delivery as well as approaches to block the delivery of drugs from the nose to the brain. Even though numerous strategies have already been used to increase nose-to-brain delivery, the research for strategies inhibitory of nose-to-brain delivery seems to be scarce.

Intranasal Zotepine Nanosuspension: intended for improved brain distribution in rats

BACKGROUND

Zotepine (ZTP), an antipsychotic drug is well tolerated and particularly effective for treating negative symptoms of psychosis. But is limited by low oral bioavailability caused by substantial first pass metabolism and thereby less amount of drug reaches the brain due to blood brain barrier (BBB).

OBJECTIVES

Since ZTP displays dose dependent side effects, purpose of the contemporary study is to develop zotepine loaded nanosuspension (ZTP-NS) for increased brain targeting in rats at lower doses.

METHODS

ZTP-NS is prepared by two techniques viz., sonoprecipitation (SP) and combination technique (high pressure homogenization preceded by precipitation) by employing various stabilizers. Optimized ZTP-NS was characterized for particle size, solid state, morphology and solubility. In vitro drug release of ZTP and formulations was conducted using Franz diffusion cell. Stability study was performed at different temperature conditions. Pharmacokinetic study was performed in Wistar rats to determine the bioavailability and brain distribution of ZTP after intra-nasal (IN) and intravenous (IV) administration. Histopathology of brain was done after repeated administration of IN ZTP dispersion and NS up to 14 days.

RESULTS

The optimized ZTP-NS formulated with Pluronic F-127 (0.3%w/v), Hydroxypropyl methyl cellulose E15 (0.3%w/v) and soya lecithin (0.4%w/v) showed particle size of 519.26 ± 10.44 nm & 330.2 ± 12.90 nm and zeta potential of -21.7 ± 1.39 mV and - 18.26 ± 1.64 mV with sonoprecipitation and combination technique respectively. In vitro drug release was high (81.79 ± 3.23%) for ZTP-NS prepared by combination technique. Intranasal NS resulted in high brain concentrations of 8.6 fold (sonoprecipitation) and 10.79-fold hike in AUC_0-24h in contrast to intravenous ZTP solution. Histopathology results reveal no significant changes in brain microscopic images.

CONCLUSION

ZTP-NS was successfully developed, characterized and found that nanosuspension is a favorable approach for intranasal delivery of zotepine. Graphical abstract Graphical abstract representing zotepine drawbacks, nanosuspension preparation, characterization and pharmacokinetic study in rats.

Enhanced intranasal insulin delivery by formulations and tumor protein-derived protein transduction domain as an absorption enhancer

One of the key factors for successful development of an intranasal insulin formulation is an absorption enhancer that would deliver insulin efficiently across nasal membranes without causing damage to mucosa or inducing protein aggregation under physiological conditions. In the present study, a protein transduction domain (PTD1) and its L-form with the double substitution A6L and I8A (PTD4), derived from human translationally controlled tumor protein, were used as absorption enhancers. PTD4 exhibited higher compatibility with insulin in terms of biophysical properties analyzed using μDSC, DLS, and CD. In addition, thermodynamic properties indicated stable complex formation but higher propensity of protein aggregation. Arginine hydrochloride (ArgHCl) was used to suppress protein aggregation and carbohydrates (i.e., mannitol, sucrose, and glycerin) were used as osmolytes in the formulation. The relative bioavailability of insulin co-administered intranasally using PTD4, 16 mg/mL glycerin and 100 mM ArgHCl was 58% and that using PTD4, 1 w/v% sucrose, and 25 mM ArgHCl was 53% of the bioavailability obtained via the subcutaneous route. These values represented a remarkable increase in bioavailability of intranasal insulin, causing a significant decrease in blood glucose levels within one hour. The pharmacokinetic properties of intranasal absorption were dependent on the concentration of carbohydrates used. These results suggest that the newly designed formulations with PTD represent a useful platform for intranasal delivery of insulin and other biomolecules.

Modification of translationally controlled tumor protein-derived protein transduction domain for improved intranasal delivery of insulin

Carrier peptides, termed protein transduction domains (PTDs), serve as provide promising vehicles for intranasal delivery of macromolecular drugs. A mutant PTD derived from human translationally controlled tumor protein (TCTP-PTD 13, MIIFRALISHKK) was reported to provide enhanced intranasal delivery of insulin. In this study, we tested whether its efficiency could be further improved by replacing amino acids in TCTP-PTD 13 or changing the amino acids in the carrier peptides from the l- to the d-form. We assessed the pharmacokinetics of PTD-mediated transmucosal delivery of insulin in normal rats and the activity of insulin in alloxan-induced diabetic rats. The safety/toxicity profile of the carrier peptides was evaluated based on the release of lactate dehydrogenase (LDH) in nasal wash fluid, body weight changes, and several biochemical parameters. Pharmacokinetic and pharmacodynamic studies showed that the l-form of a double substitution A6L, I8A (MIIFRLLASHKK), designated as l-TCTP-PTD 13M2 was the most effective carrier for intranasal insulin delivery. The relative bioavailability of insulin co-administered intranasally with l-TCTP-PTD 13M2 was 37.1% of the value obtained by the subcutaneous route, which was 1.68-fold higher than for insulin co-administered with l-TCTP-PTD 13. Moreover, co-administration of insulin plus l-TCTP-PTD 13M2 reduced blood glucose levels compared to levels in diabetic rats treated with insulin plus l-TCTP-PTD 13. There was no evidence of toxicity. These results suggest that the newly designed PTD is a useful carrier peptide for the intranasal delivery of drugs or biomolecules.

Aerosolized liposomes with dipalmitoyl phosphatidylcholine enhance pulmonary absorption of encapsulated insulin compared with co-administered insulin

OBJECTIVE

We have previously shown that aerosolized liposomes with dipalmitoyl phosphatidylcholine (DPPC) enhance the pulmonary absorption of encapsulated insulin. In this study, we aimed to compare insulin encapsulated into the liposomes versus co-administration of empty liposomes and unencapsulated free insulin, where the DPCC liposomes would serve as absorption enhancer.

SIGNIFICANCE

The present study provides the useful information for development of noninvasive treatment of diabetes.

METHODS

Co-administration of empty DPPC liposomes and unencapsulated free insulin was investigated in vivo to assess the potential enhancement in protein pulmonary absorption. Co-administration was compared to DPPC liposomes encapsulating insulin, and free insulin.

RESULTS

DPPC liposomes enhanced the pulmonary absorption of unencapsulated free insulin; however, the enhancing effect was lower than that of the DPPC liposomes encapsulating insulin. The mechanism of the pulmonary absorption of unencapsulated free insulin by DPPC liposomes involved the opening of epithelial cell space in alveolar mucosa, and not mucosal cell damage, similar to that of the DPPC liposomes encapsulating insulin. In an in vitro stability test, insulin in the alveolar mucus layer that covers epithelial cells was stable. These findings suggest that, although unencapsulated free insulin spreads throughout the alveolar mucus layer, the concentration of insulin released near the absorption surface is increased by the encapsulation of insulin into DPPC liposomes and the absorption efficiency is also increased.

CONCLUSION

We revealed that the encapsulation of insulin into DPPC liposomes is more effective for pulmonary insulin absorption than co-administration of DPPC liposomes and unencapsulated free insulin.

Nanotechnological applications for the control of pulmonary infections

Pulmonary infections are the major global problem. According to the global burden of disease study, lower respiratory infections were ranked third among the leading causes of death after ischaemic heart disease and cerebrovascular disease. Despite the availability of treatment options and diagnostic methods, the severity of pulmonary infections is increasing due to the emergence of multiple drug resistance and lack of sensitivity in pathogenic microbes.

In this context, nanotechnology based treatment therapies have emerged as a promising approach to circumvent the limitations of conventional therapies and also manage the problem of drug resistance in pulmonary infections. The present chapter is focused on the global status of existing management strategies of pulmonary infections and their limitations. Moreover, the role of nanotechnology for the management of pulmonary infections with a special reference to different type of nanomaterials has also been discussed.

Effect of surface charge on the brain delivery of nanostructured lipid carriers in situ gels via the nasal route

The aim of this study was to investigate the influence of the nanocarrier surface charge on brain delivery of a model hydrophilic drug via the nasal route. Anionic and cationic nanostructured lipid carriers (NLCs) were prepared and optimized for their particle size and zeta potential. The optimum particles were incorporated in poloxamer in situ gels and their in vivo behavior was studied in the plasma and brain after administration to rats. Optimum anionic and cationic NLCs of size <200 nm and absolute zeta potential value of ≈ 34 mV were obtained. Toxicity study revealed mild to moderate reversible inflammation of the nasal epithelium in rats treated with the anionic NLCs (A7), and destruction of the lining mucosal nasal epithelium in rats treated with the cationic NLCs (C7L). The absolute bioavailability of both drug loaded anionic and cationic NLCs in situ gels was enhanced compared to that of the intranasal solution (IN) of the drug with values of 44% and 77.3%, respectively. Cationic NLCs in situ gel showed a non significant higher Cmax (maximum concentration) in the brain compared to the anionic NLCs in situ gel. Anionic NLCs in situ gel gave highest drug targeting efficiency in the brain (DTE%) with a value of 158.5 which is nearly 1.2 times that of the cationic NLCs in situ gel.

On employing a translationally controlled tumor protein-derived protein transduction domain analog for transmucosal delivery of drugs

Protein transduction domains (PTDs) are recognized as promising vehicles for the delivery of macromolecular drugs. We have previously shown that a region in the N-terminus (residues 1-10) of translationally controlled tumor protein (TCTP) contains a PTD (TCTP-PTD), MIIYRDLISH, which can serve as a vehicle for the delivery of macromolecules into the cells and tissues. In the current study, we evaluated the potential and safety of TCTP-PTD and its three mutant analogs as nasal absorption enhancers for delivery of drugs. We conducted this evaluation employing insulin as test drug. We examined the degree to which insulin was absorbed in nasal mucosa and also if any mucosal damage occurs following such nasal delivery of insulin using TCTP-PTDs as a vehicle. The systemic delivery of insulin was assessed by measuring the changes in blood glucose levels after nasal coadministration insulin and four PTDs. Of the three TCTP-PTD analogs examined, one, TCTP-PTD analog (MIIFRALISHKK) significantly enhanced the nasal absorption of insulin in both normal and streptozotocin-induced diabetic mice. The relative pharmacological bioavailability of insulin nasally coadministered with the TCTP-PTD analog was 21.3% relative to the subcutaneous route. Molecular association between insulin and the TCTP-PTD analog was observed by fluorescence resonance energy transfer measurements. The binding between the TCTP-PTD analog and insulin may enable the penetration of insulin through the nasal mucosa. Histological examination of mice nasal mucosa 7 days after repeated nasal administration showed no evidence of toxicity at the site of nasal administration. In this study using insulin as a test system we demonstrate that the TCTP-PTD analog offers a promising approach for nasal peptides and protein-drugs delivery.

Strategies for non-invasive delivery of biologics

Macromolecular therapeutics, in particular, many biologics, is the most advancing category of drugs over conventional chemical drugs. The potency and specificity of the biologics for curing certain disease made them to be a leading compound in the pharmaceutical industry. However, due to their intrinsic nature, including high molecular weight, hydrophilicity and instability, they are difficult to be administered via non-invasive route. This is a major quest especially in biologics, as they are frequently used clinically for chronic disorders, which requires long-term administration. Therefore, many efforts have been made to develop formulation for non-invasive administration, in attempt to improve patient compliance and convenience. In this review, strategies for non-invasive delivery, in particular, oral, pulmonary and nasal delivery, that are recently adopted for delivery of biologics are discussed. Insulin, calcitonin and heparin were mainly focused for the discussion as they could represent protein, polypeptide and polysaccharide drugs, respectively. Many recent attempts for non-invasive delivery of biologics are compared to provide an insight of developing successful delivery system.

Stability and structure of protein-lipoamino acid colloidal particles: toward nasal delivery of pharmaceutically active proteins

To circumvent the painful intravenous injection of proteins in the treatment of children with growth deficiency, anemia, and calcium insufficiency, we investigated the stability and structure of protein-lipoamino acid complexes that could be nasally sprayed. Preparations that ensure a colloidal and structural stability of recombinant human growth hormone (rhGH), recombinant human erythropoietin (rhEPO), and salmon calcitonin (sCT) mixed with lauroyl proline (LP) were established. Protein structure was controlled by circular dichroism, and very small sizes of ca. 5 nm were determined by dynamic light scattering. The colloidal preparations could be sprayed with a droplet size of 20-30 μm. The molecular structure of aggregates was investigated by all-atom molecular dynamics. Whereas a lauroyl proline capping of globular proteins rhGH and rhEPO with preservation of their active structure was observed, a mixed micelle of sCT and lipoamino acids was formed. In the latter, aggregated LP constitutes the inner core and the surface is covered with calcitonins that acquire a marked α-helix character. Hydrophobic/philic interaction balance between proteins and LP drives the particles' stability. Passage through nasal cells grown at confluence was markedly increased by the colloidal preparations and could reach a 20 times increase in the case of EPO. Biological implications of such colloidal preparations are discussed in terms of furtiveness.

Nasal route: an alternative approach for antiemetic drug delivery

INTRODUCTION

Antiemetic drugs are used in the treatment of nausea and emesis. Development of novel delivery systems for antiemetic drugs, as an alternative to conventional preparations, is important in terms of good patient compliance and improving bioavailability. The nasal route offers unique superiorities, such as fast and high drug absorption, and high patient compliance. Therefore, a considerable amount of research has been carried out on the development of nasal delivery systems for antiemetic drugs.

AREAS COVERED

This review deals with the importance of nasal delivery of antiemetic drugs and the studies performed on this subject. The first part of this review summarizes the properties of the nasal route, its advantages and limitations, parameters affecting drug absorption through nasal mucosa, nasal passage pathways and general approaches to improve nasal transport. The second part reviews the studies conducted on the development of nasal delivery systems.

EXPERT OPINION

Due to its superiorities, the nasal route could be considered as an attractive alternative to oral and parenteral routes. To overcome the barrier properties of the nasal epithelium and to enhance transport of antiemetic drugs, several approaches, including permeation enhancers, in situ gel formulations and micro- and nanoparticulate systems, have been evaluated. The results obtained are promising and indicate that nasal formulations of some antiemetic drugs may enter the market in the near future.

[Effects of sperminated pullulans on the pulmonary absorption of insulin]

Sperminated pullulans (SP) having different molecular weights (MWs) were prepared, and the enhancing effect on the pulmonary absorption of insulin in rats was examined. SP acted as enhancers of insulin absorption when a 0.1% solution was applied with insulin simultaneously and their enhancing effects depended on the MW of the SP; the same solutions exhibited low toxicity in the in vivo LDH leaching test. In the in vitro experiments using Calu-3 cells, tight junction-opening effects and a toxic effect of SP in the MTT assay were observed at lower concentrations compared with the in vivo experiments. A mucus layer might interfere with the interaction between SP and the cell surface and might suppress both these effects and toxicity. SP having a high MW will be useful for preparing safe and efficient formulations of peptide and protein drugs. The change in the localization of the tight junction proteins may be related to the permeation-enhancing mechanism of SP.

Dry powder vaccines for mucosal administration: critical factors in manufacture and delivery

Dry powder vaccine formulations have proved effective for induction of systemic and mucosal immune responses. Here we review the use of dry vaccines for immunization in the respiratory tract. We discuss techniques for powder formulation, manufacture, characterization and delivery in addition to methods used for evaluation of stability and safety. We review the immunogenicity and protective efficacy of dry powder vaccines as compared to liquid vaccines delivered by mucosal or parenteral routes. Included is information on mucosal adjuvants and mucoadhesives that can be used to enhance nasal or pulmonary dry vaccines. Mucosal immunization with dry powder vaccines offers the potential to provide a needle-free and cold chain-independent vaccination strategy for the induction of protective immunity against either systemic or mucosal pathogens.

Non-invasive systemic drug delivery: developability considerations for alternate routes of administration

Over the past few decades alternate routes of administration have gained significant momentum and attention, to complement approved drug products, or enable those that cannot be delivered by the oral or parenteral route. Intranasal, buccal/sublingual, pulmonary, and transdermal routes being the most promising non-invasive systemic delivery options. Considering alternate routes of administration early in the development process may be useful to enable new molecular entities (NME) that have deficiencies (extensive first-pass metabolism, unfavorable physicochemical properties, gastro-intestinal adverse effects) or suboptimal pharmacokinetic profiles that are identified in preclinical studies. This review article describes the various delivery considerations and extraneous factors in developing a strategy to pursue an alternate route of administration for systemic delivery. The various delivery route options are outlined with their pros and cons; key criteria and physicochemical attributes that would make a drug a suitable candidate are discussed; approaches to assess delivery feasibility, toxicity at the site of delivery, and overall developability potential are described; and lastly, product trends and their disease implications are highlighted to underscore treatment precedence that help to build scientific rationale for the pursuit of an alternate route of administration.

Rat nasal lavage biomarkers to assess preclinical irritation potential of nasal drug formulations and excipients

The goal of this study was to evaluate biomarkers of nasal mucosal damage for rapid assessment of irritancy potential of formulations in the rat nasal lavage model, a tool to facilitate nasal formulation development prior to histopathology studies. The nasal cavity of anesthetized rats was lavaged with normal saline 20 min pos-tdose. The collected fluid was analyzed for secreted total protein and biomarkers. Solutions tested include: normal saline, buffers, benzalkonium chloride (BAC), lysophosphatidylcholine (LPC), and four marketed nasal products. Total protein, lactate dehydrogenase and interleukin-1alpha biomarkers were secreted to varying degrees. BAC (0.2%) and LPC (0.5%) exhibiting the strongest response with a signal window ranging from 3.4- to 87-fold greater levels than normal saline. Buffer treatments, excipients, and most marketed nasal products yielded levels similar to normal saline. There was a weak correlation between formulation osmolarity and surface tension with any of the biomarkers. Each nasal formulation elicited a unique protein and biomarker profile with total protein secretion correlated with IL-1alpha secretion suggesting the potential for an inflammatory response. Taken together, rapid and potentially mechanistic information on the preclinical acute irritancy potential of formulations was assessed in the rat nasal lavage model by benchmarking treatments relative to controls and marketed nasal products.

Modulation of Ganciclovir Intestinal Absorption in Presence of Absorption Enhancers

The purpose of this investigation was to study the influences of absorption enhancers in increasing oral bioavailability of Ganciclovir (GAN) by assessing the transepithelial permeation across cell monolayers in vitro and bioavailability in rats in vivo. The permeation of GAN across Caco-2 and MDCK cell monolayers in the absence/presence of dimethyl-beta-cyclodextrin (DMbetaCD), chitosan hydrochloride (CH), sodium lauryl sulphate (SLS), and their combinations was studied for a 2-h period. GAN was administered to rats in absence/presence of absorption enhancers and drug contents in plasma were estimated. We found that the apparent permeability coefficient (Papp) of GAN in absence of absorption enhancers (control) were 0.261 +/- 0.072 x 10(-6) and 0.486 +/- 0.063 x 10(-6) cm/s in Caco-2 and MDCK cell monolayers, respectively, whereas in the presence of DMbetaCD, CH, SLS, and their combinations, Papp of GAN increased by 5- to 25-fold and 7- to 33-fold as compared to control in Caco-2 and MDCK cell monolayers, respectively. However, in rats, the maximum enhancement in bioavailability of GAN during coadministration of these absorption enhancers was only fivefold compared to GAN control. To conclude, the absorption enhancers-DMbetaCD, CH, SLS, and their combinations demonstrated significant improvement in transepithelial permeation and bioavailability of GAN.

Effects of a sperminated gelatin on the nasal absorption of insulin

The effects of a sperminated gelatin (SG), which was prepared as a candidate absorption enhancer by the addition of spermine to gelatin, on the nasal absorption of insulin, were examined in rats. The AUC of immuno-reactive insulin levels in the plasma after nasal administration of insulin were increased 5.3-fold by addition of 0.2% SG, and the plasma glucose levels fell in a manner dependent on the insulin levels. In Calu-3 cell monolayer permeation experiments, SG showed significant enhancing effects on 5(6)-carboxyfluorescein (CF), FITC-dextran (MW 4400, FD4) and insulin. Evaluation of the tight junctions in the Calu-3 cell monolayers based on the Renkin molecular sieving function suggests that the pore occupancy/length ratio of the permeation pathways for water-soluble molecules in the tight junctions increases, while the equivalent cylindrical pore radius is not changed by SG treatment. SG may transform the true tight junctions, which act as a barrier for water-soluble molecules, into pathways for CF and FD4 to increase their number. SG is a good candidate for a safe absorption enhancer to produce a slight modification of the permeability of the paracellular pathway of mucosal membranes, while retaining the sieving property of the epithelial membranes.

Effect of cationized gelatins on the paracellular transport of drugs through caco-2 cell monolayers

Cationized gelatins, candidate absorption enhancers, were prepared by addition of ethylenediamine or spermine to gelatin and the effects of the resulting ethylenediaminated gelatin (EG) and sperminated gelatin (SG) on the paracellular transport of 5(6)-carboxyfluorescein (CF), FITC-dextran-4 (FD4), and insulin through caco-2 cell monolayers were examined. The Renkin function was used for characterization of the paracellular pathway and changes in the pore radius (R) and pore occupancy/length ratio (epsilon/L) calculated from the apparent permeability coefficients (P(app)) of CF and FD4 are discussed. Ethylenediaminetetraacetic acid (EDTA) increased the R of the caco-2 cell monolayer and the P(app) of all compounds examined was markedly increased by the addition of EDTA. On the other hand, EG and SG did not increase R and their enhancing effects were not as strong as those of EDTA. The increase in epsilon/L could be the enhancing mechanism for the cationized gelatins. The number of pathways for water-soluble drugs, such as CF and FD4, in the caco-2 monolayers could be increased by the addition of the cationized gelatins. The ratios of the permeability coefficients of insulin (observed/calculated based on the Renkin function) suggest that insulin undergoes enzymatic degradation during transport which is not inhibited by enhancers.

Rapid-onset intranasal delivery of metoclopramide hydrochloride. Part I. Influence of formulation variables on drug absorption in anesthetized rats

Intranasal (IN) administration is a promising approach for rapid-onset delivery of medications and to circumvent their first-pass elimination when taken orally. Metoclopramide (MCP) is a potent antiemetic, effective even for preventing emesis induced by cancer chemotherapy. The feasibility of developing an efficacious intranasal formulation of metoclopramide has been undertaken in this study. The nasal absorption of MCP was studied in anesthetized rats over 60min using the in vivo in situ technique. The influence of several formulation variables, vis., pH and the addition of preservative, viscosity and absorption enhancing agents on the nasal MCP absorption was examined. The data obtained showed that MCP was well absorbed nasally where almost 90% of the drug was absorbed after 60min from the rat nasal cavity. The MCP absorption was pH-dependant such that the apparent first-order rate constant of absorption (K(app)) was almost tripled when the pH of the solution was increased from 5 to 8. However, deviation from the classical pH-partition theory was observed pointing to the role of aqueous pore pathway in MCP nasal absorption. The K(app) was significantly increased (P<0.05) by incorporation of 0.01% of the preservative benzalkonium chloride. Conversely, increasing the solution viscosity by the use of hydroxylpropyl methylcellulose adversely affected the rate of absorption. The use of enhancers namely sodium deoxycholate, sodium cholate, chitosan low and high molecular weight, protamine sulphate and poly-l-arginine resulted in significant increase in MCP absorption. The highest promoting effect was observed with the bile salt sodium deoxycholate where about 92% of the drug was absorbed in 25min from the rat nasal cavity and the K(app) showed more than two-fold increase as compared to control (from 0.0452 to 0.1017min(-1)).

Rapid-onset intranasal delivery of metoclopramide hydrochloride Part II: Safety of various absorption enhancers and pharmacokinetic evaluation

In the present study, several nasal absorption enhancers, used in metoclopramide hydrochloride (MCP HCl) nasal solutions, have been screened for their possible damaging effect in the in vitro human erythrocytes lysis experiment. Moreover, the in vivo leaching of biological markers from the rat nasal epithelium was used as a quantitative assessment for possible nasal mucosal irritation whereby the extent of release of total protein and lactate dehydrogenase (LDH) in the nasal lavage fluid was determined. Results showed that insignificant hemolysis from normal saline (P<0.05) occurred with the enhancer protamine sulphate while poly-l-arginine and sodium cholate demonstrated very low (<15%) hemolysis and caused insignificant protein and LDH release from the rat nasal mucosa. Conversely, sodium deoxycholate and chitosan polymers (either of low or high molecular weight) showed high (>60%) hemolysis in vitro and the release of the biological markers in vivo was significantly higher (P<0.05) than the control solution (no enhancer). A significant correlation (P<0.05) existed between the enhancement effect of MCP HCl nasal absorption and the amounts of protein (r=0.85) and LDH (r=0.88). Furthermore, the pharmacokinetics of MCP HCl was determined after intravenous (IV), per-oral and intranasal administration of 10mg drug dose in rabbits. The application of a nasal spray (NS) solution containing 0.5% sodium cholate resulted in a significant improvement (P<0.05) in both the rate and extent of absorption of MCP HCl where the T(max) achieved was 23.3min as compared to 50min in case of the oral solution while the area under the serum concentration-time curve (AUC(0-infinity)) were 506.1, 434.9 and 278.7microg/mlmin for IV, NS and oral solutions, respectively. These values corresponded to absolute bioavailabilities of 87.21 and 55.61% for the NS and oral solutions, respectively. It could thus be concluded that NS of MCP HCl represents a viable approach to achieving rapid and high systemic drug absorption during the emergency treatment of severe emesis.

Pharmacokinetic Advantage of an Intranasal Preparation of a Novel Anti-osteoporosis Drug, L-Asp-Hexapeptide-Conjugated Estradiol

We examined the usefulness of intranasal (i.n.) administration of a novel osteotropic prodrug of estradiol, estradiol-17beta-succinate-(L-aspartate)6 (E2.17D6), for selective drug delivery to bone. E2.17D6 alone or with 5% 2,6-di-O-methyl-beta-cyclodextrin (DMbetaCD), 5% beta-cyclodextrin (betaCD), or 10% hydroxypropyl cellulose (HPC) as an absorption enhancer was administered to ovariectomized (OVX) mice via the i.n. route. The oral and nasal bioavailability after p.o. or i.n. administration of E2.17D6 (3.7 micromol/kg) in mice amounted to 9.9 and 23.0% of the dose, respectively. The values of nasal bioavailability of E2.17D6 administered with DMbetaCD, betaCD, and HPC were 74.9, 55.8, and 49.1%, respectively. The plasma concentration of E2.17D6 after i.n. administration of E2.17D6-DMbetaCD decreased rapidly to the endogenous level by 6 h, but the concentration in the bone was about 200 times higher than that in plasma, and decreased slowly over a period of about a week. When E2 (total dose 4.4 micromol/kg, i.n., every 3rd day) was administered to OVX mice for 35 d, bone mineral density (BMD), liver weight, and uterus weight increased, whereas E2.17D6-DMbetaCD (total dose 0.44 to 8.8 micromol/kg, i.n., every 7th day) increased only BMD in a dose-dependent manner. In conclusion, intranasally administered E2.17D6-DMbetaCD has a potent antiosteoporotic effect without side effects, and has potential to provide an improved quality of life for patients with osteoporosis.

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.

Effect of chitosan on the intranasal absorption of salmon calcitonin in sheep

The effects of a chitosan-based delivery system on the pharmacokinetics of intranasally administered salmon calcitonin (sCT) were investigated in a sheep model. In particular, the feasibility of producing a formulation with a comparable or improved bioavailability and/or less variability than the currently marketed nasal product (Miacalcin nasal spray, Novartis Pharmaceuticals) was assessed. A comparator (control) formulation comprising sCT solution was also tested. Sheep (n=6) were dosed intranasally according to a randomized crossover design. The intranasal sCT dose was 1100 IU (equivalent to approximately 17 IU kg-1). After completion of the nasal dosing legs, five of the sheep received 300 IU sCT (equivalent to approximately 5 IU kg-1) by subcutaneous injection to estimate relative bioavailability. After intranasal or subcutaneous dosing, serial blood samples were taken and plasma separated by centrifugation before measuring sCT concentrations by ELISA. Pharmacokinetic (non-compartmental) and statistical (analysis of variance or non-parametric alternative) analyses were performed. No systemic or local adverse effects were observed following intranasal or subcutaneous administration of sCT. The mean relative bioavailability of sCT from the chitosan solution was improved twofold compared with Miacalcin nasal spray and threefold compared with sCT control solution. Inter-animal variability in sCT absorption appeared to be lower with use of the chitosan-based solution compared with the control solution or commercial product. Based on the reported sheep data, a chitosan delivery system could offer the potential to significantly improve the intranasal absorption of sCT and reduce the variability in absorption. In the clinical setting, this may allow relatively lower doses of the drug to be given intranasally and/or lead to improvements in the efficacy or quality of intranasal therapy.

Effect of aminated gelatin on the nasal absorption of insulin in rats

Absorption enhancers, which increase the permeability of drugs through epithelial membranes without damaging them, are especially useful for intranasal administration of peptide drugs. In this study, aminated gelatins, candidate enhancers, having different numbers of amino groups were prepared from gelatin (H-gelatin, isoelectric point = 9.0, MW 100 kDa) and a partial gelatin hydrolysate (L-gelatin, isoelectric point = 8.0, MW 5 kDa), and the enhancing effects on the nasal absorption of insulin, used as a model peptide drug, and 5(6)-carboxyfluorescein (CF), a paracellular marker, were examined in rats. The enhancing effect on insulin and CF depends on the MW and number of amino groups. A high correlation between the enhancing effects on insulin and CF was observed and this suggests that an increase in the paracellular permeability is the mechanism governing the nasal absorption-enhancement of aminated gelatins, at least as far as insulin and CF are concerned. The enhancing mechanism might be shared with other cationic polymers having absorption-enhancing effects.

Cyclodextrins in nasal delivery of low-molecular-weight heparins: in vivo and in vitro studies

PURPOSE

To test the hypothesis that cyclodextrins reversibly enhance nasal absorption of low-molecular-weight heparins (LMWHs) and to investigate the mechanisms by which cyclodextrins enhance LMWH absorption via the nose.

METHODS

Absorption of LMWHs was studied by measuring plasma anti-factor Xa activity after nasal administration of various LMWH formulations to anesthetized rats. In vivo reversibility studies were performed to investigate if the effects of cyclodextrins are reversible and diminish with time. The absorption-enhancing mechanisms of cyclodextrins were investigated in cell culture model. The transport of enoxaparin and mannitol, changes in transepithelial electrical resistance (TEER), and distribution of tight junction protein ZO-1 were investigated.

RESULTS

Formulations containing 5% dimethyl-beta-cyclodextrin (DMbetaCD) produced the highest increase in the bioavailability of LMWH preparations tested. In vivo reversibility studies with 5% DMbetaCD showed that the effect of the absorption enhancer at the site of administration diminished with time. Transport studies using 16HBE14o(-) cells demonstrated that the increase in the permeability of enoxaparin and mannitol, reduction in TEER, and the changes in the tight junction protein ZO-1 distribution produced by 5% DMbetaCD were much greater than those produced by beta-cyclodextrin (betaCD) or hydroxyl-propyl-beta-cyclodextrin (HPbetaCD).

CONCLUSIONS

Of the cyclodextrins tested, DMbetaCD was the most efficacious in enhancing absorption of LMWHs both in vivo and in vitro. The study also suggests that cyclodextrins enhance nasal drug absorption by opening of cell-cell tight junctions.

Alkanoylsucroses in nasal delivery of low molecular weight heparins: in-vivo absorption and reversibility studies in rats

The efficacy of alkanoylsucroses in enhancing nasal absorption of low molecular weight heparin (LMWH) and the time span of action of these agents on the nasal membrane has been investigated. In this regard, LMWH formulated with alkanoylsucroses was administered nasally to anaesthetized male Sprague-Dawley rats and the absorption of LMWH was determined by measuring plasma antifactor Xa activity. The duration of action of these agents at the site of administration was investigated by an in-vivo reversibility study. The potency and efficacy of dodecanoylsucrose was compared with that of sodium glycocholate. Alkanoylsucroses used in this study include dodecanoylsucrose, decanoylsucrose and octanoylsucrose. These agents enhance nasal absorption of enoxaparin in a dose-dependent and chain-length-dependent manner. Of the agents tested, dodecanoylsucrose was found to be the most potent in enhancing nasal absorption of LMWH. The bioavailability of enoxaparin formulated with alkanoylsucroses was increased by several folds compared with enoxaparin formulated in saline. The reversibility study with dodecanoylsucrose showed that the effect of alkanoylsucroses faded away with time and the duration of action of this agent at the site of administration was 120-140 min. Dodecanoylsucrose was found to be twice as potent as sodium glycocholate. Overall, the nasal absorption of LMWH was effectively enhanced by co-administration of alkanoylsucroses and the effect of alkanoylsucroses on nasal epithelium was found to be reversible. The potency of these agents depends on their hydrophobic chain lengths.

Enhancing effect of chitosan on nasal absorption of salmon calcitonin in rats: comparison with hydroxypropyl- and dimethyl-beta-cyclodextrins

Two types of chitosan, i.e. the free amine (CS J) and the glutamate salt (CS G), were evaluated for their enhancing effect on in vivo nasal absorption of salmon calcitonin (sCT) in rats. The results were subsequently compared with beta-cyclodextrins, one of the most commonly studied enhancers. Solutions containing sCT and chitosan (0-1.25% w/v) in isotonic phosphate buffers (IPB; pH 3.0-6.0) were nasally administered at the dose of 10 IU/kg. The plasma calcium lowering effect in each sCT-treated rat was determined by calculating the total percent decrease in plasma calcium (%D). CS J showed an increase in %D as the solution pH was decreased in accordance with the increased ionization and hydration of the free amine chitosan at the more acidic pH. However, CS G showed an increase in %D with increasing pH, with maximum hypocalcemic effect observed at pH 6.0. At their optimal pH (4.0 for CS J and 6.0 for CS G), the absorption enhancing effect of both chitosans was concentration dependent from 0.25 to 1.0% and leveled off at 1.25%. Using specific RIA, the absolute bioavailability of sCT after comparison with i.v. administration was determined to be 2.45, 1.91, and 1.22% for 1% CS J, 5% dimethyl-beta-cyclodextrin (DM-beta-CD) and control group (intranasal (in) sCT alone), respectively. Although the absolute nasal bioavailability seemed to be low when compared to the i.v. administration, the inclusion of 1% CS J resulted in two-fold increase in the AUC(0-180) of plasma sCT relative to that of the control group. Addition of 5% DM-beta-CD also led to 1.56-fold increase in absorption over the control group. All the enhancers showed significant absorption enhancement (P<0.05) with the highest effect observed with CS J. In conclusion, cationic polymer chitosan may have promising potential as a safe and effective nasal absorption enhancer of sCT.

The effects of water-soluble cyclodextrins on the histological integrity of the rat nasal mucosa

The aim of this study was to investigate the effect of highly water-soluble cyclodextrins (CDs) on the histological integrity of the nasal mucosa. In order to evaluate their effects, the in vivo single and repeated nasal exposure studies were performed using male Wistar rats. The rat nasal cavity was excised after an application of various CD solutions at different times. The morphological appearances of the rat nasal mucosae were analyzed with the light microscopic and the scanning electron microscopic studies. By utilizing 5-min exposure of each CD solution to the nasal mucosa, no tissue damage was visible for 1.5% w/v beta-CD and 5 and 20% w/v hydroxypropyl beta-CD (HP beta-CD), and the effects were quite similar to controls. However, using 20% w/v randomly methylated beta-CD (RM beta-CD) showed severe damage on the integrity of nasal mucosa. The severity was similar to 1% w/v polyoxyethylene-9-lauryl ether or l% w/v sodium deoxycholate. Meanwhile, 30 or 60 min exposure to 10% w/v HP beta-CD or RM beta-CD resulted in no obvious mucosal damage. In addition, in vivo repeated dosing of RM beta-CD did not show any toxicity up to 20% w/v. These results suggest that at least, less than 10% w/v CD solutions do not induce gross tissue damage and can keep the histological integrity of the nasal mucosa.

Analysis of transient and reversible effects of poly-L-arginine on the in vivo nasal absorption of FITC-dextran in rats

We have investigated whether poly-L-arginine, with a mean molecular weights of 8.9 and 45.5 kDa (poly-L-Arg (10) and poly-L-Arg (50)), can induce transient and reversible effects involving enhancement of the nasal absorption of fluorescein isothiocyanate-labeled dextran (MW 4.4 kDa, FD-4) and determined the main pathway for the increased transport of FD-4 in rats in vivo. Pre-administration and repeated administration studies were conducted involving the selection of different time intervals between intranasal administration of poly-L-Arg and administration of FD-4, with and without poly-L-Arg, to characterize these transient and reversible effects. The degradation of poly-L-Args in a diluted nasal drip was determined from the fluorescence of degraded poly-L-Arg-fluorescamine products. In the pre-administration study, poly-L-Arg exhibited a transient effect on the increased nasal FD-4 absorption depending on its molecular weight, associated with the degradation rate of poly-L-Arg in mucus. In the repeated administration study, additional poly-L-Arg produced similarly enhanced FD-4 absorption. Confocal laser scanning microscopy showed that fluorescence of FD-4 after co-administration of poly-L-Arg (50) was confined mainly to the paracellular spaces. In conclusion, poly-L-Arg exhibited molecular weight-dependent transient and reversible effects on the enhancement of nasal FD-4 absorption paracellularly in rats in vivo. The enzymatic degradation of poly-L-Arg is one of the key determinants of the transient effect on in vivo enhanced absorption of FD-4.