Emmeline Marttin

Nasal mucociliary clearance as a factor in nasal drug delivery

The nasal mucociliary clearance system transports the mucus layer that covers the nasal epithelium towards the nasopharynx by ciliary beating. Its function is to protect the respiratory system from damage by inhaled substances. Impairment of nasal mucociliary clearance can result in diseases of the upper airways. Therefore, it is important to study the effects of drugs and drug excipients on nasal mucociliary clearance. A large number of methods are used to assess mucociliary clearance. These methods study the effects of drug and excipients on the mucociliary system in vitro or in vivo in animals and humans. In some cases, the results of different in vitro and in vivo measurements do not correlate well. In vitro methods, especially ciliary beat frequency measurements, have been demonstrated to be valuable tools for toxicity screening. However, in vivo studies are essential to confirm the safety of nasal drug formulations. Nasal mucociliary clearance also has implications for nasal drug absorption. Drugs are cleared rapidly from the nasal cavity after intranasal administration, resulting in fast systemic drug absorption. Several approaches are discussed to increase the residence time of drug formulations in the nasal cavity, resulting in improved nasal drug absorption. However, more experimental evidence is needed to support the conclusion that this improved absorption is caused by a longer residence time of the nasal drug formulation.

Cyclodextrins in nasal drug delivery.

Nasal drug delivery is an attractive approach for the systemic delivery of high potency drugs with a low oral bioavailability due to extensive gastrointestinal breakdown and high hepatic first-pass effect. For lipophilic drugs nasal delivery is possible if they can be dissolved in the dosage form. Peptide and protein drugs often have a low nasal bioavailability because of their large size and hydrophilicity, resulting in poor transport properties across the nasal mucosa. Cyclodextrins are used to improve the nasal absorption of these drugs by increasing their aqueous solubility and/or by enhancing their nasal absorption. With several cyclodextrins very efficient nasal drug absorption has been reported, but also large interspecies differences have been found. Studies concerning the safety of cyclodextrins in nasal drug formulations demonstrate the non-toxicity of the cyclodextrins and also clinical data show no adverse effects. Therefore, some cyclodextrins can be expected to become effective and safe excipients in nasal drug delivery.

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

AbstractPurpose. The assessment of the effects of nasal absorption enhancers on the rat nasal epithelium and membrane permeability in vivo after a single nasal dose of the enhancers. Methods. The release of marker compounds (protein, cholesterol and acid phosphatase) from the nasal epithelium was measured using a lavage technique. The nasal membrane permeability was determined after intravenous administration of a systemic tracer (FITC-albumin). Results. The effects of the absorption enhancers could be classified into four categories. The first consisted of HPβCD (5%), DMβCD (2%) and RAMEB (2%) and was not different from the control (physiological saline). For the second category, DMβCD (5%), effects were significantly higher than for the control. The third category, SGC (1%), was more active than DMβCD (5%) but less active than the last group. The fourth, most membrane damaging, category consisted of STDHF (1%), laureth-9 (1%) and LPC (1%). Administration of these three enhancers also resulted in release of acid phosphatase, indicating that severe membrane damage occurred. The release of cholesterol from nasal epithelium was largely dependent on the cholesterol solubilisation of the absorption enhancers. The amount of cholesterol released by laureth-9 and LPC was the largest. Conclusions. The results of this in vivo study are in agreement (i.e. similarity in rank order) with morphological and ciliotoxicity studies of nasal absorption enhancers, demonstrating that this invivo model is a valuable tool to classify nasal absorption enhancers according to their effects on the rat nasal epithelium.

Confocal laser scanning microscopic visualization of the transport of dextrans after nasal administration to rats: effects of absorption enhancers.

AbstractPurpose. To visualize the transport pathway(s) of high molecular weight model compounds across rat nasal epithelium in vivousing confocal laser scanning microscopy. Furthermore, the influence of nasal absorption enhancers (randomly methylated β-cyclodextrin and sodium taurodihydrofusidate) on this transport was studied. Methods. Fluorescein isothiocyanate (FITC)-labelled dextrans with a molecular weight of 3,000 or 10,000 Da were administered intranasally to rats. Fifteen minutes after administration the tissue was fixed with Bouin. The nasal septum was surgically removed and stained with Evans Blue protein stain or DiIC18(5) lipid stain prior to visualization with the confocal laser scanning microscope. Results. Transport of FITC-dextran 3,000 across nasal epithelium occurred via the paracellular pathway. Endocytosis of FITC-dextran 3,000 was also shown. In the presence of randomly methylated β-cyclodextrin 2% (w/v) similar transport pathways for FITC-dextran 3,000 were observed. With sodium taurodihydrofusidate 1% (w/v) the transport route was also paracellular with endocytosis, but cells were swollen and mucus was extruded into the nasal cavity. For FITC-dextran 10,000 hardly any transport was observed without enhancer, or after co-administration with randomly methylated β-cyclodextrin 2% (w/v). Co-administration with sodium taurodihydrofusidate 1% (w/v) resulted in paracellular transport of FITC-dextran 10,000, but morphological changes, i.e. swelling of cells and mucus extrusion, were observed. Conclusions. Confocal laser scanning microscopy is a suitable approach to visualize the transport pathways of high molecular weight hydrophilic compounds across nasal epithelium, and to study the effects of absorption enhancers on drug transport and cell morphology.

The effect of nasal drug formulations on ciliary beating in vitro

In order to estimate the potential of nasal drug formulations to influence ciliary beating, ciliary beat frequency (CBF) measurements were performed in vitro, using chicken embryo trachea and a photo-electric registration device. The effects of nasal prescription and non-prescription drug formulations were studied and compared with a number of investigational nasal drug formulations containing estradiol, dihydroergotamine mesylate and salmon calcitonin. The influence of all formulations on CBF was related to the effects of formulation additives such as preservatives and nasal absorption enhancers on the ciliated tissue. For almost all nasal drug formulations, the preservatives used in the formulations (e.g. benzalkonium chloride, chlorobutanol) play a decisive role in the observed ciliostatic effects. Methylated β-cyclodextrins, used as nasal absorption enhancers/solubilizers in the investigational formulations, appeared to be relatively non-toxic for the ciliated tissue, having similar effects on CBF as physiological saline. After dilution five times, most drug formulations studied showed a moderate ciliostatic effect, but marked differences could still be detected. The present study demonstrates that CBF measurements in vitro are a valuable tool in the design of safe nasal drug formulations.

The effect of methylated β-cyclodextrins on the tight junctions of the rat nasal respiratory epithelium:: Electron microscopic and confocal laser scanning microscopic visualization studies

The nasal absorption enhancer randomly methylated beta-cyclodextrin (RAMEB) is thought to increase the paracellular permeability of the nasal epithelium by opening of the tight junctions. The effects of RAMEB on the cytoskeleton of the rat nasal epithelium in vivo were determined by confocal laser scanning microscopy (CLSM). The effects on the tight junctions of the rat nasal epithelium were also investigated, using transmission electron microscopy (TEM) of thin sections. The effects of RAMEB were compared with those of the absorption enhancer sodium taurodihydrofusidate (STDHF). Fifteen minutes after nasal administration of 2% RAMEB in vivo, the distribution of cytoskeletal actin was comparable to the untreated control, suggesting that RAMEB does not cause opening of the tight junctions via cytoskeletal interactions. In contrast, administration of 1% STDHF resulted in changes in the actin staining. Furthermore, with TEM severe damage of the nasal epithelium was observed after treatment with 1% STDHF. Ultrastructural changes of the tight junctions were not apparent in TEM sections after treatment with 2% RAMEB. In conclusion, CLSM and TEM are suitable methods to visualize the effects of absorption enhancers on nasal epithelial morphology.

Acute histopathological effects of benzalkonium chloride and absorption enhancers on rat nasal epithelium in vivo

Abstract The aim of the study was to determine the acute effects of nasal absorption enhancers on the morphology of the rat nasal epithelium in vivo. Examples of three classes of enhancers were studied: the cyclodextrins dimethyl-β-cyclodextrin 2% (w/v) and randomly methylated-β-cyclodextrin 2% (w/v), the bile salt sodium glycocholate 1% (w/v), and the phospholipid L-α-lysophosphatidylcholine 1% (w/v). The preservative benzalkonium chloride 0.01% (w/v) was investigated for reasons of comparison. The compounds were dissolved in physiological saline (0.9% NaC1) and administered intranasally to anaesthetized rats. After 15 min the nasal cavity was fixated with Bouin and the tissue was processed for light microscopic examination. Morphological changes induced by physiological saline were graded as negligible or minor, and those of benzalkonium chloride as minor to major. The effects were mainly located in the respiratory epithelium. The effects of randomly methylated β-cyclodextrin and dimethyl-β-cyclodextrin were also minor and comparable to those of physiological saline. After administration of sodium glycocholate, large amounts of mucus were discharged from goblet cells and pyknosis occurred. l -α-lysophosphatidylcholine resulted in disruption of the epithelium, and damage was found not only in the respiratory epithelium but also in the olfactory epithelium. In conclusion, the acute effects of methylated β-cyclodextrins on the nasal epithelium morphology are relatively mild, and comparable to or less than those of the preservative benzalkonium chloride. Sodium glycocholate shows irreversible damage, and l -α-lysophosphatidylcholine is the most damaging absorption enhancer.

Cyclodextrins in Nasal Drug Delivery: Trends and Perspectives

Cyclodextrins (CDs) are used as excipients in nasal drug formulations because they act as solubilisers and/or absorption enhancers. With several CDs very efficient nasal drug absorption has been reported, but large interspecies differences have been found. Studies concerning the safety of CDs in nasal drug formulations demonstrate the non-toxicity of the CDs and also clinical data show no adverse effects. Therefore, some CDs can be expected to become effective and safe excipients in nasal drug delivery.

Simplified solid-phase extraction method for determination of dihydroergotamine in rabbit and human serum using high-performance liquid chromatography with fluorescence detection

A rapid, selective and sensitive method for the determination of dihydroergotamine (DHE) in serum was developed. Dihydroergocristine (DHEC) was used as an internal standard. Human and rabbit serum samples were extracted using commercial solid-phase cyano (CN) columns. Proteins were washed from these columns with pure acetonitrile, resulting in clean extracts. Extracts were subsequently separated by HPLC in an isocratic way, using a reversed-phase C18 analytical column. Fluorometric detection was performed at excitation and emission wavelengths of 277 and 348 nm, respectively. Calibration curves with amounts of DHE ranging from 2 to 32 ng, were linear. The limit of detection found for DHE was 0.2 ng, extracted from 0.5 ml rabbit or from 2.5 ml human serum. The limit of quantification in serum of both species was 0.7 ng. The method has been shown to be suitable for monitoring DHE in serum during pharmacokinetic studies in rabbits.

Efficacy and Safety of Cyclodextrins in Nasal Drug Delivery

The intranasal application of tobacco snuff, cocaine, various psychotropic and hallucinogenic agents has been known for a long time. It is therefore surprising that only in the past two decades intranasal administration of systemic drugs has attracted much attention. The nasal route circumvents the first-pass elimination associated with oral drug delivery. Furthermore, nasal drug delivery is an attractive alternative to the injection therapy, it is easily accessible and suitable for self administration.