Prodrugs for nasal drug delivery

Essential considerations towards development of effective nasal antibiotic formulation: features, strategies, and future directions

INTRODUCTION

Intranasal antibiotic products are gaining popularity as a promising method of administering antibiotics, which provide numerous benefits, e.g. enhancing drug bioavailability, reducing adverse effects, and potentially minimizing resistance threats. However, some issues related to the antibiotic substances and nasal route challenges must be addressed to prepare effective formulations.

AREAS COVERED

This review focuses on the valuable points of nasal delivery as an alternative route for administering antibiotics, coupled with the challenges in the nasal cavity that might affect the formulations. Moreover, this review also highlights the application of nasal delivery to introduce antibiotics for local therapy, brain targeting, and systemic effects that have been conducted. In addition, this viewpoint provides strategies to maintain antibiotic stability and several crucial aspects to be considered for enabling effective nasal formulation.

EXPERT OPINION

In-depth knowledge and understanding regarding various key considerations with respect to the antibiotic substances and nasal route delivery requirement in preparing effective nasal antibiotic formulation would greatly improve the development of nasally administered antibiotic products, enabling better therapeutic outcomes of antibiotic treatment and establishing appropriate use of antibiotics, which in turn might reduce the chance of antibiotic resistance and enhance patient comfort.

A Novel Calcium Channel Blocker: Etripamil: What is the Future of Intranasal Drug Delivery in the Treatment of Cardiac Arrhythmias?

Symptomatic paroxysmal cardiac arrhythmias are common cardiac conditions that lead to a decreased quality of life, increased healthcare costs, and significant morbidity. Many cardiac arrhythmias increase in frequency with age, and as the elderly population continues to increase, so will the incidence and prevalence of cardiac arrhythmias. The long-term treatment options for patients with paroxysmal arrhythmias include ablation procedures and daily oral antiarrhythmics. Acute management entails vagal maneuvers, intravenous antiarrhythmics, and synchronized cardioversion. However, there are limited treatment options for patients with less frequent and less severe arrhythmias, ablation refractory disease, or who are poor candidates for ablative procedures, For abortive therapy, oral anti-arrhythmic medications are ineffective due to their slow onset of action and intravenous medications require treatment at an acute care facility, which is both costly and stressful to the patient. Etripamil is a novel intranasal non-dihydropyridine calcium channel blocker that has begun phase III clinical trials for the treatment of paroxysmal supraventricular tachycardias. Due to its intranasal mode of delivery, etripamil has a rapid onset of action, and could feasibly be administered by the patient themselves. Clinical phase II trials of etripamil in moderate to high doses demonstrated efficacy comparable to the standard of care, and took an average of 3 minutes from drug administration to conversion to sinus rhythm. In this article, we have conducted an extensive literature review of intranasal drug delivery, calcium channel blockers, and etripamil, to discuss the future possibilities of using this new medication.

The potential of intranasal delivery of nanocrystals in powder form on the improvement of zaleplon performance: in-vitro, in-vivo assessment

OBJECTIVE

The present work focuses on improving zaleplon (ZAP) performance through nanosizing its insoluble particles which were then delivered intranasally in powder form.

SIGNIFICANCE

Since nanopowders have an exceptional ability to cross cell membrane, their absorption is facilitated in the solid form. Hence, delivering insoluble ZAP nanocrystals (NC) through intranasal route improves its bioavailability due to both nanosization and the escape of hepatic metabolism.

METHODS

Nanocrystals were prepared by anti-solvent precipitation followed by probe sonication in presence of Soluplus^®, Poloxamer-188 (0.25%), sodium lauryl sulfate (0.5%), and mannitol. Physicochemical evaluation of the prepared NC was done by DSC and XRPD. TGA was performed for stability detection. Ex vivo permeation study through isolated cattle nasal mucosal membrane, in addition to an in vivo bioavailability study was performed for assessment of the prepared NC.

RESULTS

Nanosization to 200 nm contributed to the enhancement in dissolution ∼100% within 30 min and reduced half-life to 1.63 min. Confirmation of adsorption of polymers over NC' surface was elucidated. TGA confirmed their thermal stability. Ex vivo permeation study showed a 2.7 enhancement ratio in favor of the prepared NC. Both the extent and rate of NC absorption through nasal mucosa of rabbits were significantly higher (p ˂ .05) than in case of oral tablets. The relative bioavailability of NC was increased 3.14 times as compared to the Sleep aid^® tablets.

CONCLUSION

The intranasal delivery of nanoscale ZAP powder proved to be a successful alternative to oral formulations that suffer poor absorption and limited bioavailability.

Recent Advances and Novel Approaches for Nose to Brain Drug Delivery for Treatment of Migraine

Background:

Nasal drug delivery has been used since ancient times for therapeutic and recreational purposes. For the last decades, nasal drug delivery has been extended for drug delivery to the brain. Therefore, it is important to understand the several physiological and physicochemical factors of the nose for brain drug delivery.

Objective:

A major highlight of the present review article is the several aspects of the nose to brain delivery for migraine treatment. This review will help to understand different factors which are needed to be considered for intra-nasal formulations to achieve the desired therapeutic effects.

Method:

There are different drug delivery routes available for migraine treatment. Nasal route of administration may be optimal for migraine treatment which has better drug concentration in the brain. These approaches may be associated with limiting the adverse effects of drug therapeutics.

Results:

A list of total FDA approved approaches has been provided. Novel approaches used for drug targeting to get maximum drug concentration in the brain have been highlighted. Several novel drug delivery approaches such as nanoparticle, nanoemulsion, microspheres, etc. have been reported and better therapeutic effects have been observed. Among the novel approaches, some of them are currently under either Phase II or Phase III development but may prove to offer better clinical effects. These approaches would become the alternate choice for migraine treatment with patients experiencing symptoms consistent with gastrointestinal dysfunction associated with migraine.

Conclusion:

Intra-nasal administration of drugs for migraine treatment may offer an interesting alternative for achieving therapeutic effects of drugs which are comparable to the parenteral route. Nasal drug delivery can be an alternative route of drug administration for migraine treatment to achieve better bioavailability.

Engineering the Mucus Barrier

Mucus selectively controls the transport of molecules, particulate matter, and microorganisms to the underlying epithelial layer. It may be desirable to weaken the mucus barrier to enable effective delivery of drug carriers. Alternatively, the mucus barrier can be strengthened to prevent epithelial interaction with pathogenic microbes or other exogenous materials. The dynamic mucus layer can undergo changes in structure (e.g., pore size) and/or composition (e.g., protein concentrations, mucin glycosylation) in response to stimuli that occur naturally or are purposely administered, thus altering its barrier function. This review outlines mechanisms by which mucus provides a selective barrier and methods to engineer the mucus layer from the perspective of strengthening or weakening its barrier properties. In addition, we discuss strategic design of drug carriers and dosing formulation properties for efficient delivery across the mucus barrier.

Development of a nanogel-based nasal vaccine as a novel antigen delivery system

INTRODUCTION

Nasal vaccination is one of the most effective immunization methods because it can induce effective antigen-specific immune responses not only at the mucosal site of administration but also at distant mucosal surfaces, as well as in the systemic compartment. Based on this advantage, many nasal vaccines are being developed and some have been licensed and marketed for clinical use. However, some have been withdrawn because of unacceptable adverse events such as inactivated influenza vaccine administrated with a heat-labile enterotoxin of Escherichia coli as an adjuvant. Thus, it is important to consider both the efficacy and safety of nasal vaccines. Areas covered: This review describes the benefits of cholesteryl group-bearing pullulan (CHP) nanogels for nasal vaccine delivery and vaccine development identified on Pubmed database with the term 'Nanogel-based nasal vaccine'. Expert commentary: CHP nanogels have been developed as novel drug delivery system, and a cationic CHP nanogels have been demonstrated to induce effective immunity as a nasal vaccine antigen carrier. Since vaccine antigens incorporated into CHP nanogels have exhibited no brain deposition after nasal administration in mice and nonhuman primates, the vaccine seems safe, and could be a promising new delivery system.

The effect of drugs and other compounds on the ciliary beat frequency of human respiratory epithelium

BACKGROUND

Cilia in the human respiratory tract play a critical role in clearing mucus and debris from the airways. Their function can be affected by a number of drugs or other substances, many of which alter ciliary beat frequency (CBF). This has implications for diseases of the respiratory tract and nasal drug delivery. This article is a systematic review of the literature that examines 229 substances and their effect on CBF.

METHODS

MEDLINE was the primary database used for data collection. Eligibility criteria based on experimental design were established, and 152 studies were ultimately selected. Each individual trial for the substances tested was noted whenever possible, including concentration, time course, specific effect on CBF, and source of tissue.

RESULTS

There was a high degree of heterogeneity between the various experiments examined in this article. Substances and their general effects (increase, no effect, decrease) were grouped into six categories: antimicrobials and antivirals, pharmacologics, human biological products, organisms and toxins, drug excipients, and natural compounds/other manipulations.

CONCLUSION

Organisms, toxins, and drug excipients tend to show a cilioinhibitory effect, whereas substances in all other categories had mixed effects. All studies examined were in vitro experiments, and application of the results in vivo is confounded by several factors. The data presented in this article should be useful in future respiratory research and examination of compounds for therapeutic and drug delivery purposes.

Solid lipid nanoparticles for nose to brain delivery of haloperidol: in vitro drug release and pharmacokinetics evaluation

In the present study, haloperidol (HP)-loaded solid lipid nanoparticles (SLNs) were prepared to enhance the uptake of HP to brain via intranasal (i.n.) delivery. SLNs were prepared by a modified emulsification–diffusion technique and evaluated for particle size, zeta potential, drug entrapment efficiency, in vitro drug release, and stability. All parameters were found to be in an acceptable range. In vitro drug release was found to be 94.16±4.78% after 24 h and was fitted to the Higuchi model with a very high correlation coefficient (R²=0.9941). Pharmacokinetics studies were performed on albino Wistar rats and the concentration of HP in brain and blood was measured by high performance liquid chromatography. The brain/blood ratio at 0.5 h for HP-SLNs i.n., HP sol. i.n. and HP sol. i.v. was 1.61, 0.17 and 0.031, respectively, indicating direct nose-to-brain transport, bypassing the blood–brain barrier. The maximum concentration (C_max) in brain achieved from i.n. administration of HP-SLNs (329.17±20.89 ng/mL, T_max 2 h) was significantly higher than that achieved after i.v. (76.95±7.62 ng/mL, T_max 1 h), and i.n. (90.13±6.28 ng/mL, T_max 2 h) administration of HP sol. The highest drug-targeting efficiency (2362.43%) and direct transport percentage (95.77%) was found with HP-SLNs as compared to the other formulations. Higher DTE (%) and DTP (%) suggest that HP-SLNs have better brain targeting efficiency as compared to other formulations.

Formulation and evaluation of thermosensitive biogels for nose to brain delivery of doxepin

Thermoreversible biogels can serve as effective systems for delivery of drugs through nose with increased nasal residence time. The objective of this study was to use chitosan and glycerophosphate based thermoreversible systems for delivery of doxepin to brain through intranasal administration. Formulations were prepared by admixture of suitable dilutions of chitosan and glycerophosphate with or without polyethylene glycol, followed by addition of the antidepressant doxepin hydrochloride. Both systems were evaluated for gelling characteristics, rheology, mucoadhesion, in vitro release, and ex vivo permeation through sheep nasal mucosa. In vivo efficacy was evaluated in Swiss albino mice through the forced swim test. Nasal tissues of mice subjected to repeated exposure to formulation were evaluated histopathologically. Both formulations gelled rapidly at 37°C, returned to sol state on cooling, and exhibited thixotropy. Addition of polyethylene glycol decreased the glycerophosphate content required for gelation and rendered the formulation isotonic. Both gels showed good mucoadhesion, enhanced drug permeation, and provided prolonged in vitro release at 37°C. Efficacy of the formulation in treated groups was inferred from the measured pharmacodynamic parameter and histopathological reports of formulation treated groups showed no significant local toxicity. The biogels could be potential systems for effective drug delivery to brain via nose.

Intranasal zolmitriptan for the treatment of acute migraine

OBJECTIVE

To review the pharmacokinetics, efficacy, tolerability, and patient acceptance of zolmitriptan nasal spray (NS).

BACKGROUND

Gastroparesis may delay or diminish the absorption of oral triptans, and nausea or vomiting may do the same and/or make it difficult to take a tablet. Some migraineurs require or prefer faster relief than oral medications provide. Injectable triptans provide the fastest drug delivery into the bloodstream, but many patients are reluctant to use them. Nasal sprays may address some of the problems with tablets and injectables while still providing rapid absorption of drug.

METHODS

Non-systematic review.

RESULTS

Significant levels of zolmitriptan NS are detectable in plasma within 2-5 minutes, and the rapid absorption is due to early uptake through the nasal mucosa. In 2 randomized trials, users of zolmitriptan NS were significantly more likely than placebo recipients to be pain-free at 15 minutes post-dose, the first time point measured, and about half of patients had sustained response at 24 hours. Studies in which patients could treat a migraine of any severity have documented significant headache response or relief with zolmitriptan NS at 10 minutes. In one trial, the rate of total symptom relief was significantly better with the NS than with placebo from 30 minutes post-dose. The most common side effect of zolmitriptan NS is unusual taste. Patient satisfaction studies indicate that zolmitriptan NS is appreciated for its speed of onset, ease of use, reliability, and overall efficacy.

CONCLUSIONS

Zolmitriptan NS provides onset of headache relief within 10 minutes for some patients and quickly abolishes some of the major migraine symptoms. Good candidates are migraineurs whose episodes rapidly escalate to moderate-to-severe pain and those who have morning migraine, have a quick time to vomiting, or have failed oral triptans.

The effect of polymer coatings on physicochemical properties of spray-dried liposomes for nasal delivery of BSA

This work describes the development of spray dried polymer coated liposomes composed of soy phosphatidylcholine (SPC) and phospholipid dimyristoyl phosphatidylglycerol (DMPG) coated with alginate, chitosan or trimethyl chitosan (TMC), that are able to penetrate through the nasal mucosa and offer enhanced penetration over uncoated liposomes when delivered as a dry powder. All the liposome formulations, loaded with BSA as model antigen, were spray-dried to obtain powder size and liposome size in a suitable range for nasal delivery. Although coating resulted in some reduction in encapsulation efficiency, levels were still maintained between 60% and 69% and the structural integrity of the entrapped protein and its release characteristics were maintained. Coating with TMC gave the best product characteristics in terms of entrapment efficiency, glass transition (T(g)) and mucoadhesive strength, while penetration of nasal mucosal tissue was very encouraging when these liposomes were administered as dispersions although improved results were observed for the dry powders.

Preparation and in vitro characterization of mucoadhesive hydroxypropyl guar microspheres containing amlodipine besylate for nasal administration

Amlodipine besylate microspheres for intranasal administration were prepared with an aim to avoid first-pass metabolism, to achieve controlled blood level profiles and to improve therapeutic efficacy. Hydroxypropyl Guar, a biodegradable polymer, was used in the preparation of microspheres by employing water in oil emulsification solvent evaporation technique. The formulation variables were drug concentration, emulsifier concentration, temperature, agitation speed and polymer concentration. All the formulations were evaluated for particle size, particle shape and surface morphology by scanning electron microscopy, percentage yield, drug entrapment efficiency, in vitro mucoadhesion test, degree of swelling and in vitro drug diffusion through sheep nasal mucosa. The microspheres obtained were free flowing, spherical and the particles ranged in size from 13.4±2.38 μm to 43.4±1.92 μm very much suitable for nasal delivery. Increasing polymer concentration resulted in increased drug entrapment efficiency and increased particle size. Amlodipine besylate was entrapped into the microspheres with an efficiency of 67.2±1.18 % to 81.8±0.64 %. The prepared microspheres showed good mucoadhesion properties, swellability and sustained the release of the drug over a period of 8 h. The data obtained were analysed by fitment into various kinetic models; it was observed that the drug release was matrix diffusion controlled and the release mechanism was found to be non-Fickian. Stability studies were carried out on selected formulations at 5±3°, 25±2°/60±5% RH and 40±2°/75±5% RH for 90 days. The drug content was observed to be within permissible limits and there were no significant deviations in the in vitro mucoadhesion and in vitro drug diffusion characteristics.

Intranasal drug delivery: an efficient and non-invasive route for systemic administration: focus on opioids

Intranasal administration is a non-invasive route for drug delivery, which is widely used for the local treatment of rhinitis or nasal polyposis. Since drugs can be absorbed into the systemic circulation through the nasal mucosa, this route may also be used in a range of acute or chronic conditions requiring considerable systemic exposure. Indeed, it offers advantages such as ease of administration, rapid onset of action, and avoidance of first-pass metabolism, which consequently offers for example an interesting alternative to intravenous, subcutaneous, oral transmucosal, oral or rectal administration in the management of pain with opioids. Given these indisputable interests, fentanyl-containing formulations have been recently approved and marketed for the treatment of breakthrough cancer pain. This review will outline the relevant aspects of the therapeutic interest and limits of intranasal delivery of drugs, with a special focus on opioids, together with an in-depth discussion of the physiological characteristics of the nasal cavity as well as physicochemical properties (lipophilicity, molecular weight, ionisation) and pharmaceutical factors (absorption enhancers, devices for application) that should be considered for the development of nasal drugs.

Lipophilic derivatives of leu-enkephalinamide: in vitro permeability, stability and in vivo nasal delivery

Leu-enkephalin is an endogenous pain modulating opioid pentapeptide. Its development as a potential pharmaceutic has been hampered by poor membrane permeability and susceptibility to enzymatic degradation. The addition of an unnatural amino acid containing a lipidic side chain at the N-terminus and the modification of the C-terminus to a carboxyamide was performed to enhance the nasal delivery of the peptide. Two lipidic derivatives with varying side chain lengths (C(8)-Enk-NH(2) (1), C(12)-Enk-NH(2) (2)) and their acetylated analogues were successfully synthesised. Caco-2 cell monolayer permeability and Caco-2 cell homogenate stability assays were performed. C(8)-Enk-NH(2) (1) and its acetylated analogue Ac-C8-Enk-NH(2) (3) exhibited apparent permeabilities (mean±SD) of 2.51±0.75×10(-6)cm/s and 1.06±0.62×10(-6), respectively. C12-Enk-NH(2) (2) exhibited an apparent permeability of 2.43±1.26×10(-6) cm/s while Ac-C12-Enk-NH(2) (4) was not permeable through the Caco-2 monolayers due to its poor solubility. All analogues exhibited improved Caco-2 homogenate stability compared to Leu-Enk-NH(2) with t(½) values of: C8-Enk-NH(2) (1): 31.7 min, C(12)-Enk-NH(2) (2): 14.7 min, Ac-C8-Enk-NH(2) (3): 83 min, Ac-C(12)-Enk-NH(2) (4): 27 min. However, plasma stability assays revealed that the diastereoisomers of C8-Enk-NH(2) (1) did not degrade at the same rate, with the l isomer (t(1/2)=8.9 min) degrading into Leu-enkephalinamide and then des-Tyr-Leu-Enk-NH(2), whereas the d isomer was stable (t(1/2)=120 min). In vivo nasal administration of C(8)-Enk-NH(2) to male rats resulted in concentrations of 5.9±1.84×10(-2) μM in the olfactory bulbs, 1.35±1.01×10(-2) μM in the brain and 6.53±1.87×10(-3) μM in the blood 10 min after administration.

Intranasal delivery--modification of drug metabolism and brain disposition

Intranasal route continues to be one of the main focuses of drug delivery research. Although it is generally perceived that the nasal route could avoid the first-pass metabolism in liver and gastrointestinal tract, the role of metabolic conversions in systemic and brain-targeted deliveries of the parent compounds and their metabolites should not be underestimated. In this commentary, metabolite formations after intranasal and other routes of administration are compared. Also, the disposition of metabolites in plasma and brain after nasal administrations of parent drugs, prodrugs and preformed metabolites will be discussed. The importance and implications of metabolism for future nasal drug development are highlighted.

Mucus-penetrating nanoparticles for drug and gene delivery to mucosal tissues

Mucus is a viscoelastic and adhesive gel that protects the lung airways, gastrointestinal (GI) tract, vagina, eye and other mucosal surfaces. Most foreign particulates, including conventional particle-based drug delivery systems, are efficiently trapped in human mucus layers by steric obstruction and/or adhesion. Trapped particles are typically removed from the mucosal tissue within seconds to a few hours depending on anatomical location, thereby strongly limiting the duration of sustained drug delivery locally. A number of debilitating diseases could be treated more effectively and with fewer side effects if drugs and genes could be more efficiently delivered to the underlying mucosal tissues in a controlled manner. This review first describes the tenacious mucus barrier properties that have precluded the efficient penetration of therapeutic particles. It then reviews the design and development of new mucus-penetrating particles that may avoid rapid mucus clearance mechanisms, and thereby provide targeted or sustained drug delivery for localized therapies in mucosal tissues.

Air-Liquid Interface Culture of Serially Passaged Human Nasal Epithelial Cell Monolayer forIn VitroDrug Transport Studies

The objective of this study was to establish a drug transport study using human nasal epithelial (HNE) cell monolayers cultured by the air-liquid interface (ALI) method using serum-free medium (BEGM:DME/F12, 50:50). The cells were developed and characterized in comparison to those that have been previously cultured by the liquid-covered culture (LCC) method. The epithelial cell monolayer cultured by the ALI method resulted in a significantly higher transepithelial electrical resistance value (3,453 +/- 302 ohm x cm(2)) that was maintained (>1,000 ohm x cm(2)) for up to 20 days compared with that cultured by the LCC method. Observation by scanning electron microscopy revealed mature cilia after 2 weeks in the ALI culture, while flatten unhealthy ciliated cells were observed in the LCC method. After 21 days, higher level of MUC5AC and 8 mRNA were expressed in ALI culture which confirmed the secretory differentiation of HNE monolayers in vitro. No significant difference in the permeability coefficients of a model hydrophilic marker ((14)C-mannitol) and a lipophilic drug (budesonide) was observed between the two conditions on day 7. The passage 2-3 of the HNE monolayer using ALI condition retained the morphology and differentiated features of normal epithelium. Thus it would be a suitable model for in vitro nasal drug delivery studies.

Transfection of primary human nasal epithelial cells using a biodegradable poly (ester amine) based on polycaprolactone and polyethylenimine as a gene carrier

The purpose of this study was to prepare and characterize poly (ester amine) (PEA)/pGL3 complexes and investigate their transfection efficiency in human nasal epithelial (HNE) cells. Particle size, zeta potential, and gel retardation characteristics of PEA /pGL3 complexes were also measured. After treatment of DNase-I, protection and release assay of PEA/pGL3 complexes were performed. To assess the transfection efficiency and cytotoxicity, measurement of relative luciferase activity and MTS assay were performed. PEA/pGL3 complexes showed effective and stable DNA condensation with the particle sizes below 200 nm, implicating their potential for intracellular delivery. PEA/pGL3 complexes successfully transfected into the HNE cells with higher viability of the cells. These results suggested that, the PEA can be used as an efficient cationic polymeric vehicle which provides a versatile platform for further investigation of structure property relationship along with the controlled degradation, significant low cytotoxicity, and high transfection efficiency of the primary HNE cells.

The synthesis of amphipathic prodrugs of 1,2-diol drugs with saccharide conjugates by high regioselective enzymatic protocol

A facile, high regioselective enzymatic synthesis approach for the preparation of amphipathic prodrugs with saccharides of mephenesin and chlorphenesin was developed. Firstly, transesterification of two drugs with divinyl dicarboxylates with different carbon chain length was performed under the catalysis of Candida antarctica lipase acrylic resin and Lipozyme in anhydrous acetone at 50 degrees C, respectively. A series of lipophilic derivatives with vinyl groups of mephenesin and chlorphenesin were prepared. The influences of different organic solvents, enzyme sources, reaction time, and the acylation reagents on the synthesis of vinyl esters were investigated. And then, protease-catalyzed high regioselective acylation of D-glucose and D-mannose with vinyl esters of mephenesin and chlorphenesin gave drug-saccharide derivatives in good yields. The studies of lipophilicity and hydrolysis in vitro of prodrugs verified that drug-saccharide derivatives had amphipathic properties, and both lipophilic and amphipathic drug derivatives had obvious controlled release characteristics.

Transport of anti-allergic drugs across the passage cultured human nasal epithelial cell monolayer

The purpose of this study was to investigate the nasal absorption characteristics of a series of anti-allergic drugs across the human nasal epithelial cell monolayer, which was passage cultured by the liquid-covered culture (LCC) method on Transwell. Characterization of this cell culture model was achieved by bioelectric measurements and morphological studies. The passages 2--4 of cell monolayers exhibited the TEER value of 1731+/-635 Omega cm(2) after 2 days of seeding and maintained high TEER value for 4--6 days. Morphological study by TEM and SEM showed the existence of the tight junctions, and the cuboidal shaped epithelial cells monolayer. A series of anti-allergic drugs, albuterol hemisulfate, albuterol, fexofenadine HCl, dexamethasone, triamcinolon acetonide, and budesonide were selected as model compounds for transport studies. All the drugs were assayed using reversed-phase HPLC under isocratic conditions. Results indicated that within the logP (apparent 1-octanol/water partition coefficient) range from --1.58 (albuterol) to 3.21 (budesonide), there existed 100-fold difference in the apparent permeability coefficients (P(app)). A log-linear relationship was shown between the drug logP and the P(app) across passaged human nasal epithelial monolayers. The amount of fexofenadine HCl and dexamethasone across passaged human nasal cell monolayers was concentration-dependent in the direction of apical to basolateral. The direction dependent transport studies were investigated among all these drugs and no significant difference in the two directions was observed. In conclusion, this LCC passaged human nasal epithelial culture model may be a useful in vitro model for studying the passive transport processes in nasal drug delivery.

Studies on the in vivo hypoglycemic activities of two medicinal plants used in the treatment of diabetes in Jordanian traditional medicine following intranasal administration

The claimed hypoglycemic activities of Paronychia argentea Lam. (Caryophyllaceae) and Teucrium polium L. (Labiatae), two traditionally widely used medicinal plants in Jordan were evaluated using normoglycemic and alloxan induced hyperglycemic rabbits by intranasal administration of the plant crude extracts (10%) in a vehicle containing 5% (w/w) Pluronic F127. No significant difference was observed between the extract treated and non-treated control animals receiving only water.

The use of human nasal in vitro cell systems during drug discovery and development

The nasal route is widely used for the administration of drugs for both topical and systemic action. At an early stage in drug discovery and during the development process, it is essential to gain a thorough insight of the nasal absorption potential, metabolism and toxicity of the active compound and the components of the drug formulation. Human nasal epithelial cell cultures may provide a reliable screening tool for pharmaco-toxicological assessment of potential nasal drug formulations. The aim of this review is to give an overview of the information relevant for the development of a human nasal epithelial cell culture model useful during drug discovery and development. A primary goal in the development of in vitro cell culture systems is to maintain differentiated morphology and biochemical features, resembling the original tissue as closely as possible. The potential and limitations of the existing in vitro human nasal models are summarized. The following topics related to cell culture methodology are discussed: (i) primary cultures versus cell lines; (ii) cell-support substrate; (iii) medium and medium supplements; and (iv) the air-liquid interface model versus liquid-liquid. Several considerations with respect to the use of in vitro systems for pharmaceutical applications (transport, metabolism, assessment of ciliary toxicity) are also discussed.

The influence of absorption enhancers on nasal absorption of acyclovir

The objective of this work was to increase the nasal absorption of acyclovir by using absorption enhancers. Acyclovir was selected as a model drug. A rat in situ nasal perfusion technique was utilized in the investigation to examine the rate and extent of absorption of acyclovir. In vitro enzymatic drug degradation study was carried out with rat nasal washings. Various experimental conditions such as nasal perfusion rate, pH of the perfusion medium and concentrations of absorption enhancers such as sodium deoxycholate, hydroxypropyl beta-cyclodextrin, sodium caprate, sodium tauroglycocholate and EDTA were optimized. Nasal absorption of acyclovir was pH dependent. Initial absorption rate constants were determined by the plot of log% remaining amount of drug in perfusate vs time. It was found maximum at pH 7.4 and decreased at lower and higher pH conditions. In in vitro enzymatic degradation study, no measurable degradation was observed during first week. The extent of drug absorption was increased via absorption enhancers. In vivo studies were carried out for the optimized formulation in rabbits and the pharmacokinetics parameters of nasal solution were compared with oral solution. Hydroxypropyl beta-cyclodextrin appeared to be more effective for enhancing the nasal absorption of acyclovir than the other absorption enhancers. The order of increasing absorption of acyclovir caused by the enhancers was hydroxypropyl beta-cyclodextrin>sodium deoxycholate>sodium caprate>sodium tauroglycocholate>EDTA.

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.

Chemical stability, enzymatic hydrolysis, and nasal uptake of amino acid ester prodrugs of acyclovir

The objective of this work was to improve nasal absorption of relatively impermeable small drug molecules via an amino acid prodrug approach. Acyclovir was selected as a model drug. L-Aspartate beta-ester, L-lysyl, and L-phenylalanyl esters of acyclovir were synthesized to investigate their effectiveness in enhancing nasal absorption of acyclovir. A stability study was conducted in phosphate buffer under various pH conditions at 25 and 37 degrees C. Enzymatic hydrolysis in rat nasal washings and plasma was conducted at 37 degrees C. A rat in situ nasal perfusion technique was utilized in this investigation to examine the rate and extent of nasal absorption of amino acid prodrugs. The remaining analyte concentrations in the nasal perfusate were quantitated by reversed-phase high-performance liquid chromatography. The results revealed that the L-lysyl and L-phenylalanyl esters were less stable than L-aspartate beta-ester. The stability of all three esters decreased with increasing pH and temperature. L-phenylalanyl ester is highly susceptible to plasma esterases, with an in vitro half-life 1.33 min. The rat in situ nasal perfusion study revealed that the extent of nasal absorption of acyclovir, L-lysyl and L-phenylalanyl esters was not significant (p < 1%). L-Aspartate beta-ester was absorbed to the extent of approximately 8% over 90 min of perfusion at an initial drug concentration of 100 microM. Nasal absorption of L-aspartate beta-ester of acyclovir was inhibited by L-asparagine but not by a dipeptide glycylsarcosine (Gly-Sar). The enhancement of acyclovir nasal absorption from the L-aspartate beta-ester prodrug suggests that nasal uptake of this prodrug probably involves an active transport system.

Prodrugs in nasal drug delivery

Prodrugs have been used to overcome poor solubility, insufficient stability, incomplete absorption across biological membranes and premature metabolism to active species. This review examines the importance of various physicochemical factors affecting nasal absorption of drugs. Novel trends in nasal prodrug development in the areas of targeted delivery to the CNS and selective targeting of the nutrient transporter system of the nasal mucosa have received considerable attention.