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

Effect of Formulation Variables on the Nasal Permeability and Stability of Naloxone Intranasal Formulations

Naloxone is an opioid antagonist with high affinity for μ-opioid receptor, and for this reason it is used for the emergency treatment of opioid overdose. Originally, it was available only as an injectable product. However, for the ease of administration, intranasal (IN) formulations have also become available. These IN formulations contain preservatives and stabilizers such as benzalkonium chloride (BKC), benzyl alcohol (BA), and ethylenediaminetetraacetic acid (EDTA). Some of these ingredients are known to affect permeability of drugs. This study focuses on investigating the effect of formulation variables including choice of preservatives, stabilizer, and pH on the permeability and stability of naloxone IN formulations. The in vitro permeability of naloxone was evaluated employing EpiAirway™ tissue-mounted Ussing chambers. BKC was found to enhance the apparent permeability (P_app) of naloxone significantly (p < 0.05) at very low concentration, while BA caused similar enhancement at a much higher concentration. EDTA was found to decrease P_app of naloxone by lowering the pH, and the P_app of naloxone was found to decrease approximately 51-fold with the decrease in formulation pH from 6.0 to 4.0. The product stability was, however, found optimal only below pH 5.0. Thus, selection of formulation ingredients, buffering agent, and pH of IN formulation is a balancing act for achieving desired permeability and optimal stability to achieve reasonable shelf life of naloxone IN formulation.

Pulmonary Toxicity of Benzalkonium Chloride

The available toxicity data of benzalkonium chloride (BKC) clearly shows that it is toxic; however, the weight of evidence favors the view that at doses encountered in nasally and orally inhaled pharmaceutical preparations it is well tolerated. The adverse toxicological data predominantly come from in vitro and animal studies in which doses and exposure periods employed were excessive in relation to the clinical doses and their posology and, therefore, not directly applicable to the clinic. The conflict between the in vitro and animal data and the clinical experience can be reconciled by understanding some of the physicochemical properties of BKC, the nasal and respiratory tract microenvironments, the doses used, and the posology.

Nasal absorption and local tissue reaction of insulin nanocomplexes of trimethyl chitosan derivatives in rats

OBJECTIVES

The objective of this work was to explore the potential and safety of trimethyl chitosan (TMC) and PEGylated TMC for improved absorption of insulin after nasal administration.

METHODS

The nasal absorption of insulin nanocomplexes of TMC or PEGylated TMC was evaluated in anaesthetized rats. Concomitantly, the histopathological effects of these nanocomplexes on rat nasal mucosa were studied using a perfusion fixation technique.

KEY FINDINGS

All insulin nanocomplexes containing TMC or PEGylated TMC showed a 34-47% reduction in the blood glucose concentration, when the insulin absorption through the rat nasal mucosa was measured indirectly. In addition, the relative pharmacodynamic bioavailability (F(dyn)) of the formulations was found to be dependent upon the charge ratio of insulin and polymer, regardless of polymer structure. The F(dyn) apparently decreased with increasing charge ratio of insulin : polymer. Although acute alterations in nasal morphology by the formulations were affected by the charge ratio of insulin and polymer, the formulation of insulin/PEGylated TMC nanocomplexes was shown to be less toxic to the nasal epithelial membrane than insulin/TMC nanocomplexes.

CONCLUSIONS

PEGylated TMC nanocomplexes were a suitable absorption enhancer for nasal delivery of insulin.

Cyclodextrins in drug delivery

Cyclodextrins are a family of cyclic oligosaccharides with a hydrophilic outer surface and a lipophilic central cavity. Cyclodextrin molecules are relatively large with a number of hydrogen donors and acceptors and, thus, in general they do not permeate lipophilic membranes. In the pharmaceutical industry cyclodextrins have mainly been used as complexing agents to increase aqueous solubility of poorly soluble drugs, and to increase their bioavailability and stability. Studies in both humans and animals have shown that cyclodextrins can be used to improve drug delivery from almost any type of drug formulation. However, the addition of cyclodextrins to existing formulations without further optimisation will seldom result in acceptable outcome. Currently there are approximately 30 different pharmaceutical products worldwide containing drug/cyclodextrin complexes on the market.

Effects of the permeability enhancers, tetradecylmaltoside and dimethyl-β-cyclodextrin, on insulin movement across human bronchial epithelial cells (16HBE14o−)

The permeability of human bronchial epithelial cells (16HBE14o(-)) to radiolabelled insulin ([125I]insulin) formulated in the absence or presence of two different saccharide-containing permeability enhancers was investigated. In the absence of either enhancer, mannitol permeability and transepithelial electrical resistance (R(TE)) remained essentially unaffected for the duration of a 2-h experiment. Addition of either 0.125% tetradecylmaltoside (TDM) or 1% dimethyl-beta-cyclodextrin (DMBCD) to the apical surface of cells resulted in increased mannitol permeability and decreased R(TE), suggesting a loosening of cellular tight junctions and a concomitant increase in paracellular movement. Addition of [125I]insulin to the apical side of 16HBE14o(-) cells in the absence or presence of 1% DMBCD resulted in little or no [125I]insulin movement to the basolateral chamber or degradation in the apical chamber. However, in the presence of 0.125% TDM, the amount of intact [125I]insulin remaining in the apical chamber was substantially decreased, while [125I]insulin and 125I-labeled fragments were recovered on the basolateral side of the cells after 2 h. These findings provide evidence that the loosening of the tight junctions between cells achieved with DMBCD is not sufficient to stimulate transepithelial insulin movement, whereas exposure to 0.125% TDM causes an increase in [125I]insulin permeation and degradation.

Intranasal hormone replacement therapy

Although the optimal route of delivery for hormone replacement therapy has not yet been determined, desirable qualities would include good efficacy, easy administration, minimal side effects, and optimal therapeutic profile. This would potentially serve to improve patient compliance and satisfaction. The intranasal route has been evaluated for the administration of menopausal hormones and seems to fulfill these requirements. The intranasal route would also seem to be a viable alternative for drugs that are poorly absorbed after ingestion by avoiding hepatic first-pass elimination. The intranasal route is, therefore, innovative for the delivery of natural sex steroids in postmenopausal women receiving hormone replacement therapy. Early studies demonstrate that it is safe, effective, and acceptable to postmenopausal women. In addition, the nasal administration of a combination of estradiol and progesterone would seem to be an attractive way to deliver hormones to nonhysterectomized postmenopausal women. Providing alternative routes of administration may also enhance compliance.

Review on the systemic delivery of insulin via the ocular route

Systemic drug absorption from the ocular route is well known. Although there is some absorption from the conjunctival sac, the nasal meatus is the site where the majority of systemic absorption of instilled drug takes place. This article reviews the principles of systemic absorption of insulin applied topically to the eye. The physiological and pharmaceutical considerations for formulation development and the strategy of improving the systemic absorption and bioavailability of insulin are also discussed.

Bioadhesive starch microspheres and absorption enhancing agents act synergistically to enhance the nasal absorption of polypeptides

This paper investigates the effect of starch microspheres on the absorption enhancing efficiency of various enhancer systems in formulations with insulin after application in the nasal cavity of sheep. The enhancers studied were lysophosphatidylcholine, glycodeoxycholate and sodium taurodihydroxyfusidate, a bile salt derivative. The enhancers were selected on the basis of their perceived or proven mechanism of action and worked predominantly by interacting with the lipid membrane. The bioadhesive starch microspheres were shown to increase synergistically the effect of the absorption enhancers on the transport of the insulin across the nasal membrane. Dependent on the potency of the enhancer system the increment in absorption enhancement was shown to be from 1.4 times to 5 times that obtained for the absorption enhancer in solution.

Efficacy, safety and mechanism of cyclodextrins as absorption enhancers in nasal delivery of peptide and protein drugs

Cyclodextrins are used in nasal drug delivery as absorption enhancing compounds to increase the intranasal bioavailability of peptide and protein drugs. The most effective cyclodextrins in animal experiments are the methylated derivatives, dimethyl-beta-cyclodextrin and randomly methylated beta-cyclodextrin, which are active at low concentrations ranging between 2% and 5%. However, large species differences between rats, rabbits and humans exist for the nasal absorption enhancement by cyclodextrins. Based on toxicological studies of the local effects of cyclodextrins on the nasal mucosa dimethyl-beta-cyclodextrin and randomly methylated beta-cyclodextrin are considered safe nasal absorption enhancers. Their effects were quite similar to controls (physiological saline), but smaller than those of the preservative benzalkonium chloride in histological and ciliary beat frequency studies. In these studies, and in a study of the release of marker compounds after nasal administration, methylated beta-cyclodextrins were less toxic than sodium glycocholate, sodium taurodihydrofusidate, laureth-9 and L-alpha-phosphatidylcholine. Systemic toxicity after nasal cyclodextrin administration is not expected, because very low doses of cyclodextrins are administered and only very small amounts are absorbed. The mechanism of action of cyclodextrins may be explained by their interaction with the nasal epithelial membranes and their ability to transiently open tight junctions.

Effect of cod-liver oil extract on the buccal permeation of ergotamine tartrate

Ergotamine tartrate (ET) is used clinically in the treatment of migraines. However, the bioavailability of ET is rather poor following oral administration. Therefore, we tried to improve ET delivery using buccal administration. The purpose of this study was to investigate the characteristics of the permeation of ET through the hamster cheek pouch in vitro using a two-chamber diffusion cell, and to evaluate the effect of permeation enhancers on the transbuccal delivery of ET. Cod-liver oil extract (CLOE), polyoxyethylene hydrogenated castor oil (HCO 60), sodium glycocholate (GC), and sodium caprate (CA) were selected as premeation enhancers considering their low irritancy of the mucosa. When the enhancers were added to the donor cell at a 5% concentration each, the ET permeation rate markedly increased compared with that in a control not containing enhancer. Among these enhancers, CLOE exhibited the greatest effect. Because CLOE is composed of 16 kinds of fatty acids, the enhancement action of each of the major components was separately determined. As major fatty acids, palmitic acid, oleic acid, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) were selected and their enhancing effects were studied. The enhancing effect of each fatty acid was significantly lower than that of CLOE.

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.

Nasal absorption of dihydroergotamine from liquid and powder formulations in rabbits

Nasal drug delivery is an interesting route of administration for dihydroergotamine in migraine therapy. The currently available formulation contains dihydroergotamine at 4 mg/mL. For a nasal dose of 2 mg, a volume of 0.5 mL has to be administered, which sometimes leads to spillage of the formulation. The aim of the present study was to develop a nasal spray with a dihydroergotamine concentration of 10 mg/mL. To increase the solubility and stability of dihydroergotamine, randomly methylated beta-cyclodextrin was used. Liquid formulations and lyophilized powders of dihydroergotamine and randomly methylated beta-cyclodextrin were prepared. The liquid and powder formulations were compared by determining their pharmacokinetics and absolute bioavailability after nasal administration in rabbits. Nasal sprays were significantly more effective than drops in increasing the nasal bioavailability of dihydroergotamine, but the amount of randomly methylated beta-cyclodextrin in liquid sprays did not significantly alter the nasal absorption. For powder formulations, the dihydroergotamine absorption was dependent on the amount of methylated beta-cyclodextrin and powder volume, and the nasal bioavailability from the optimal powder was slightly, but not significantly, higher than that for liquids. In conclusion, the formulations investigated are a substantial improvement of the current commercial formulation, not only because the spray volume of the liquid spray can be reduced 2.5 times, but also because of the increased stability of liquid and powder sprays with randomly methylated-beta-cyclodextrin.