Nasal mucoadhesive delivery systems of the anti-parkinsonian drug, apomorphine: influence of drug-loading on in vitro and in vivo release in rabbits

Bioadhesive Nanoparticles for Local Drug Delivery

Local drug delivery is an effective strategy for achieving direct and instant therapeutic effects. Current clinical treatments have fallen short and are limited by traditional technologies. Bioadhesive nanoparticles (NPs), however, may be a promising carrier for optimized local drug delivery, offering prolonged drug retention time and steadily maintained therapeutic concentrations. In addition, the possibility of clinical applications of this platform are abundant, as most polymers used for bioadhesion are both biodegradable and biocompatible. This review highlights the major advances in the investigations of polymer-based bioadhesive nanoparticles and their innumerable applications in local drug delivery.

Design and Application in Delivery System of Intranasal Antidepressants

One of the major reasons why depressed patients fail their treatment course is the existence of the blood-brain barrier (BBB), which prevents drugs from being delivered to the central nervous system (CNS). In recent years, nasal drug delivery has achieved better systemic bioavailability and activity in low doses in antidepressant treatment. In this review, we focused on the latest strategies for delivery carriers (or formation) of intranasal antidepressants. We began this review with an overview of the nasal drug delivery systems, including nasal drug delivery route, absorption mechanism, advantages, and limitations in the nasal drug delivery route. Next, we introduced the development of nasal drug delivery devices, such as powder devices, liquid-based devices, and so on. Finally, intranasal delivery carriers of antidepressants in clinical studies, including nanogels, nanostructured lipid, liposomes nanoparticles, nanoemulsions/microemulsion, were summarized. Moreover, challenges and future perspectives on recent progress of intranasal delivery carriers in antidepressant treatments were discussed.

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.

Challenges and trends in apomorphine drug delivery systems for the treatment of Parkinson's disease

Parkinson's disease (PD) is a chronic debilitating disease affecting approximately 1% of the population over the age of 60. The severity of PD is correlated to the degree of dopaminergic neuronal loss. Apomorphine has a similar chemical structure as the neurotransmitter dopamine and has been used for the treatment of advanced PD patients. In PD patients, apomorphine is normally administered subcutaneously with frequent injections because of the compound's extensive hepatic first-pass metabolism. There is, hence, a large unmet need for alternative administrative routes for apomorphine to improve patient compliance. The present review focuses on the research and development of alternative delivery of apomorphine, aiming to highlight the potential of non-invasive apomorphine therapy in PD, such as sublingual delivery and transdermal delivery.

Development and Evaluation of a Novel Intranasal Spray for the Delivery of Amantadine

The aim of this study was to develop and characterize an intranasal delivery system for amantadine hydrochloride (AMT). Optimal formulations consisted of a thermosensitive polymer Pluronic® 127 and either carboxymethyl cellulose or chitosan which demonstrated gel transition at nasal cavity temperatures (34 ± 1°C). Rheologically, the loss tangent (Tan δ) confirmed a 3-stage gelation phenomena at 34 ± 1°C and non-Newtonian behavior. Storage of optimized formulation carboxymethyl cellulose and optimal formulation chitosan at 4°C for 8 weeks resulted in repeatable release profiles at 34°C when sampled, with a Fickian mechanism earlier on but moving toward anomalous transport by week 8. Polymers (Pluronic® 127, carboxymethyl cellulose, and chitosan) demonstrated no significant cellular toxicity to human nasal epithelial cells up to 4 mg/mL and up to 1 mM for AMT (IC50: 4.5 ± 0.05 mM). Optimized formulation carboxymethyl cellulose and optimal formulation chitosan demonstrated slower release across an in vitro human nasal airway model (43%-44% vs 79 ± 4.58% for AMT). Using a human nasal cast model, deposition into the olfactory regions (potential nose-to-brain) was demonstrated on nozzle insertion (5 mm), whereas tilting of the head forward (15°) resulted in greater deposition in the bulk of the nasal cavity.

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.

Formulation and evaluation of time-controlled triple-concentric mefenamic acid tablets for rheumatoid arthritis

A triple-concentric time-controlled release mefenamic acid (MA) tablet was developed using Carbopol and Ethocel polymers. The burst dose was programed to release immediately after an ingestion of tablet to be followed by a lag period of 2-4 h, and thereafter an 8 h controlled release of MA from core tablet. Core tablets were prepared using Carbopols 971P, 974P, 71G or 907 at various concentrations. The core tablet provided a controlled release of MA and the release rate decreased with increasing polymer concentration. Highly cross-linked Carbopol 974P released MA at a faster rate compared to release from Carbopol 971P with medium degree of cross-linking. Carbopols 71G and 971P exhibited essentially similar release rates. Carbopol 907, a linear polymer, showed fastest release of MA. The extent of uptake of dissolution medium by core tablets was inversely related to the rate of release of MA from the tablets. Compression coating of core tablet with Ethocel provided the lag period to delay release of MA from core tablet. Increase in lateral coating thickness decreased MA release and increased lag period. Compression forces applied during compression coating with Ethocel for lag period, and immediate-release MA coating for burst release did not affect the integrity of core tablet.

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.

New non-oral drug delivery systems for Parkinson's disease treatment

INTRODUCTION

Parkinson's disease (PD) remains the only neurodegenerative disorder for which there are highly effective symptomatic therapies, but still unmet needs regarding its long-term management. Levodopa (LD) remains the most effective treatment; however, chronic use is associated with potentially disabling motor complications.

AREAS COVERED

This review highlights a variety of new non-oral drug delivery strategies for non-invasive and invasive routes of drug administration for the treatment of PD. It also includes current and future trends of liposomes, solid lipid nanoparticles and biocompatible microparticles as new non-oral drug delivery systems.

EXPERT OPINION

The long-term complications and limitations of LD treatment might be improved by changing therapy from the present pulsatile stimulation to a more constant stimulation of central dopamine receptors. Stimulation of these receptors may be possible with a new non-oral drug delivery system, with the aim of achieving long-lasting and less fluctuating drug levels, minimization of peak levels and thereby reduction of side effects.

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

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

Mucoadhesive polymeric hydrogels for nasal delivery of acyclovir

The study evaluated different mucoadhesive polymeric hydrogels for nasal delivery of acyclovir. Gels containing poly-N-vinyl-2-pyrrolidone (PVP) were prepared with crosslinking achieved by irradiation with a radiation dose of 15 kGy being as efficient as 20 kGy. Gels containing chitosan and carbopol were also evaluated. The mucoadhesive properties of gels were measured by a modification of a classical tensile experiment, employing a tensile tester and using freshly excised sheep nasal mucosa. Considering the mucoadhesive force, chitosan gel and gel prepared with 3% PVP in presence of polyethylene glycol (PEG) 600 were the most efficient. The in vitro drug release depended on the gel composition. Higher release rates were obtained from PVP gels compared to chitosan or carbopol gels. The release rate of drug from PVP gels was increased further in presence of PEG or glycerol. Histopathological investigations proved that the PVP was a safe hydrogel to be used for mucosal delivery. The PEG in gel formulations caused less damages to the nasal mucosal compared to formulation containing glycerol.

Evaluation of mechanical and mucoadhesive properties of clomiphene citrate gel formulations containing carbomers and their thiolated derivatives

The aim of our study was to prepare clomiphene citrate gel formulations that possess appropriate mechanical properties, stay on the vaginal mucosa for a long period of time, and provide sustained drug release for the local treatment of human papilloma virus infections. In this respect, 1% CLM gels including polyacrylic acid (PAA) polymers such as Carbopol 934P (C934P), Carbopol 971P (C971P), Carbopol 974P (C974P) in various concentrations, and their conjugates containing thiol groups were prepared. Polyacrylic acid-cysteine (PAA-Cys) conjugates were synthesized in laboratory conditions. Mechanical properties of the gels such as hardness, compressibility, elasticity, adhesiveness, and cohesiveness were measured by TA-XTPlus texture analyzer and the vaginal mucoadhesion of formulations was investigated by mucoadhesion test. Based on obtained data, gel formulations containing C934P and its conjugate had appropriate hardness and compressibility to be applied to the vaginal mucosa and highest elasticity to show good spreadability and highest cohesion to prevent the disintegration of gel in the vagina. The mucoadhesion of the gels changed significantly depending on the polymer type and concentration (p < 0.05). The addition of conjugates containing thiol groups caused an increase in mucoadhesion (p < 0.05). The gels containing C934P-Cys showed highest adhesiveness and mucoadhesion due to the highest amount of thiol groups. A significant decrease was observed in the drug release of gel formulations as the polymer concentration increased (p < 0.05). The increase in the drug release related to the conjugate addition was not statistically significant (p > 0.05). A change in the amount of CLM was not observed in all formulations at the end of the stability test.

Permeation studies of indomethacin from different emulsions for nasal delivery and their possible anti-inflammatory effects

The purpose of this research was to develop an emulsion formulation of indomethacin (IND) suitable for nasal delivery. IND was incorporated into the oil phases of oil in water (O/W) and water in oil (W/O) emulsions. For this purpose, different emulsifying agents (Tween 80, Span 80 and Brij 58) were used in two emulsion formulations. When the effects of several synthetic membranes (nylon, cellulose, cellulose nitrate) were compared with the sheep nasal mucosa, the cellulose membrane and sheep nasal mucosa showed similar permeation properties for O/W emulsion (P > 0.05). To examine the absorption characteristics of IND, the anti-inflammatory properties of intravenous solution of IND, intranasal O/W emulsions of IND (with or without enhancers) and intranasal solution of IND (IND-Sol) were investigated in rats with carrageenan-induced paw edema. When citric acid was added to the nasal emulsion, the anti-inflammatory activity was similar to that of intravenous solution (P > 0.05). Finally, it was concluded that, intranasal administration of IND emulsion with citric acid may be considered as an alternative to intravenous and per oral administrations of IND to overcome their adverse effects.

Determination of apomorphine in canine plasma by liquid chromatography–electrospray ionization mass spectrometry and its application to a pharmacokinetic study

An LC-ESI-MS method was developed and validated for the assay of apomorphine in canine plasma using one-step liquid-liquid extraction. The analytes were separated on a Phenomenex Gemini C18 (150 mm x 2.0 mm id 3 microm) column and determined by MS in the positive ion mode. The linear range was 0.4-40 ng/mL with an LOD of 0.2 ng/mL for apomorphine in plasma. The intraday and interday precision and accuracy of quality control samples were < 5.9% RSD and < 7.5% bias for apomorphine. Extraction recoveries were > 80%. The validated method was successfully applied to analyze canine plasma samples in a pharmacokinetic study of apomorphine in dogs and detailed pharmacokinetic parameters were calculated.

Development of a sensitive and rapid liquid chromatography/tandem mass spectrometry method for the determination of apomorphine in canine plasma

A sensitive, rapid and specific quantitative liquid chromatography/tandem mass spectrometry (LC/MS/MS) method was developed and validated for the determination of apomorphine (APO) in canine plasma. The analytes were prepared using one-step liquid-liquid extraction, and analyzed on a Waters Symmetry C(18) column interfaced with triple quadrupole tandem mass spectrometer. A mixture of methanol/0.1% formic acid in water (70: 30, v/v) was employed as the isocratic mobile phase. Positive electrospray ionization was utilized as the ionization source. The analyte and clenbuterol (internal standard) were both detected using multiple reaction monitoring (MRM) mode. The limit of detection (LOD) obtained was 0.03 ng/mL. The assay was linear over the concentration range of 0.1-100 ng/mL, and provided good precision (RSD) and good accuracy (RE). The analyte was stable by using antioxidants throughout the whole study. The experimental results show that LC/MS/MS is a rapid and sensitive method to analyze APO in plasma. Finally, the proposed method was successfully applied to a pharmacokinetic study of APO after intranasal administration of 0.5 mg apomorphine to 10 healthy beagle dogs.

In situ gelling, bioadhesive nasal inserts for extended drug delivery: in vitro characterization of a new nasal dosage form

The purpose of this study was the preparation and characterization of sponge-like, in situ gelling inserts based on bioadhesive polymers. Hydrophilic polymers (carrageenan, Carbopol, chitosan, hydroxypropyl methylcellulose (HPMC) K15M and E5, sodium alginate, sodium carboxy methylcellulose (NaCMC), polyvinyl pyrrolidone (PVP) 90, xanthan gum) were dissolved with/without the model drug oxymetazoline HCl in demineralized water and lyophilized into small inserts. The drug release, water uptake, mechanical properties, X-ray diffraction and bioadhesion potential of the nasal inserts were investigated. A sponge-like structure of nasal inserts was formed with amorphous, but not with crystalline polymers during the freeze-drying process. The insert hardness increased with the glass transition temperature of the polymer (PVP25<PVP30<PVP90). The bioadhesion potential was governed by the polymer ability to interact with mucin/agar (highest for carrageenan, Carbopol, xanthan gum and NaCMC). Inserts prepared from low molecular weight polymers resulted in polymer dissolution and fast drug release (HPMC E5, Na-alginate, PVP90). The drug release from inserts prepared from high molecular weight polymers (carrageenan, Carbopol, chitosan, HPMC K15M, NaCMC, xanthan gum) was a complex interplay of osmotic forces, water uptake and electrostatic interactions between drug and polymer. The drug release decreased with higher polymer content and increased drug loading of the insert. Bioadhesive nasal inserts have a high potential as new nasal dosage form for extended drug delivery.

Nasal delivery of human growth hormone: in vitro and in vivo evaluation of a thiomer/glutathione microparticulate delivery system

It was the aim of this study to develop and evaluate a nasal microparticulate delivery system for human growth hormone (hGH) based on the thiomer polycarbophil-cysteine (PCP-Cys) in combination with the permeation mediator glutathione (GSH). Microparticles were prepared by dissolving PCP-Cys/GSH/hGH (7.5:1:1.5), PCP/hGH (8.5:1.5), and mannitol/hGH (8.5:1.5) in demineralized water, followed by lyophilization and micronization. Particles were evaluated with regard to size distribution and swelling behavior using a laser diffraction particle size analyzer. The release of fluorescence-labelled hGH from microparticles was determined in Franz diffusion chambers. In vivo studies in rats were performed comparing the nasal bioavailability achieved by PCP-Cys/GSH/hGH microparticles with that of unmodified PCP/hGH microparticles and mannitol/hGH powder. PCP-Cys/GSH/hGH and PCP/hGH microparticles showed a comparable size distribution (80% in the range of 4.8-23 microm) and swelled to almost fourfold size in phosphate-buffered saline (PBS). Both formulations exhibited almost identical sustained drug release profiles. The intranasal administration of the PCP-Cys/GSH/hGH microparticulate formulation resulted in a relative bioavailability of 8.11+/-2.15%, which represents a 3-fold and 3.3-fold improvement compared to that of PCP/hGH microparticles and mannitol/hGH powder, respectively. The study suggests that the PCP-Cys/GSH/hGH nasal microparticulate formulation might represent a promising novel tool for the systemic delivery of hGH.

Pharmaceutical applications of mucoadhesion for the non-oral routes

The adhesion of pharmaceutical formulations to the mucosal tissue offers the possibility of creating an intimate and prolonged contact at the site of administration. This prolonged residence time can result in enhanced absorption and, in combination with a controlled release of the drug, also improved patient compliance by reducing the frequency of administration. During the almost 30 years over which mucoadhesion has been studied, a considerable amount of knowledge has been gained, and much has been learned about the different mechanisms occurring at the formulation-mucus interface and the properties that affect these mechanisms. The in-vivo performance of a dosage form not only depends on the mechanisms occurring at the interface, but also on the properties of the total mucoadhesive complex: the dosage form, the mucosa and the interface between them. A wide variety of methods are used for studying mucoadhesion; some rather similar to the in-vivo situation and some mimicking the interface alone. In this review, the mucus surface, the methods used for the study of mucoadhesion, the different mechanisms involved in mucoadhesion and theories underpinning them have been described. The complexity of mucoadhesion when trying to systemize the subject will also be discussed. The last part of the review describes the buccal, nasal, ocular, vaginal and rectal routes and provides examples of what can be achieved in-vivo when using mucoadhesive formulations.

Evaluation of the clearance characteristics of various microspheres in the human nose by gamma-scintigraphy

The nasal cavity possesses many advantages as a site for drug delivery, such as; ease of administration, applicability for long-term treatments and a large surface area for absorption. One important limiting factor for nasal drug delivery is the limited time available for absorption within the nasal cavity due to mucociliary clearance. Several drug delivery systems including different kinds of microspheres have been tried for encapsulation of drugs and increasing the residence time in nasal cavity. In this study the clearance rate of three kinds of microspheres (Alginate, PLGA, and Sephadex) was determined by gamma-scintigraphy with lactose powder being used as negative control. (99m)Tc labeled microspheres were prepared using technetium pertechnetate in the presence of a potent reducing agent, stannus chloride. The labeling procedure was set in a manner that each 3-5 mg of microspheres contained 2 MBq of radioactivity. Labeling efficiency was calculated by paper chromatography using acetone as a mobile phase. Each delivery system containing 2 MBq of activity was administered into right nostril of four healthy volunteers and 1 min static views were repeated each half an hour until 4 h. Clearance rates were compared using two regions of interest (ROIs); the initial site of deposition of particles, and all of the nasopharynx region. The clearance rate of each one of microspheres was calculated after applying the physical decay corrections. The mean labeling efficiencies for Alginate, PLGA, and Sephadex microspheres were calculated as 60%, 59%, and 74%, respectively. The cleared percent of formulations from nasopharynx region after 4 h was determined as follows: PLGA microspheres 48.5 +/- 8.2%; Alginate microspheres 45.0 +/- 0.8%; Sephadex microspheres 63.1 +/- 3.4%; lactose powder 74.5 +/- 4.9%. Alginate and PLGA microspheres showed the lowest clearance rate compared to lactose powder (P < 0.0001 and P < 0.001, respectively), followed by Sephadex microspheres (P < 0.01). The clearance profiles of formulations from deposition ROI and nasopharynx ROI were identical. This study shows that Alginate and PLGA microspheres have the highest mucoadhesion properties and are suitable nasal delivery systems. Futhermore, this study proves that limiting step for the nasal clearance of nasally administered particulate systems is their dislocation from the initial site of deposition, and their following interactions with mucus layer in the rest of the nasal passage does not significantly affect the clearance time.

Spray-dried powders as nasal absorption enhancers of cyanocobalamin

The aim of this work is to describe and characterize a new spray-drying procedure for the production of nasal powders as an alternative to the conventional freeze-drying method. Cyanocobalamin was chosen as the active ingredient and loaded into five different nonsoluble vehicles with high water absorption ability. Then these hydrated particles were suspended in methylene chloride and spray-dried. Particle size, morphology, true, bulk and tapped density, percentage of compressibility, moisture content, water intake, and drug diffusion were studied and significant differences were obtained depending on the nature of the vehicle. The drying method, either the new spray- or the conventional freeze-drying, was less important. Interestingly, an inverse correlation was found between water uptake and drug diffusion. Microcrystalline cellulose, dextran microspheres, and crospovidone were chosen for an in vivo bioavailability study in rabbits. Three other nasal reference formulations and an intravenous solution were also administered. The spray-dried powders showed higher bioavailability than the three nasal reference formulations. The highest absorption enhancement was observed with cellulose microcrystalline powders, which provided a 25% mean absolute bioavailability, followed by crospovidone and dextran microspheres formulations with mean bioavailability values of 14% and 7%, respectively. In conclusion, the new spray-drying method is useful for the production of cyanocobalamin nasal powders.

Neural modulation of visuomotor functions underlying prey-catching behaviour in anurans: perception, attention, motor performance, learning

The present review points out that visuomotor functions in anurans are modifiable and provides neurophysiological data which suggest modulatory forebrain functions. The retino-tecto/tegmento-bulbar/spinal serial processing streams are sufficient for stimulus-response mediation in prey-catching behaviour. Without its modulatory connections to forebrain structures, however, these processing streams cannot manage perceptual tasks, directed attention, learning performances, and motor skills. (1) Visual prey/non-prey discrimination is based on the interaction of this processing stream with the pretectal thalamus involving the neurotransmitter neuropeptide-Y. (2) Experiments applying the dopamine agonist apomorphine in combination with 2DG mapping and single neurone recording suggest that prey-catching strategies in terms of hunting prey and waiting for prey depend on dose dependent dopaminergic adjustments in the neural macronetwork in which retinal, pretecto-tectal, basal ganglionic, limbic, and mesolimbic structures participate. (3) Visual response properties of striatal efferent neurones support the concept that ventral striatum is involved in directed attention. (4) Various modulatory loops involving the ventral medial pallium modify prey-recognition in the course of visual or visual-olfactory learning (associative learning) or are responsible for stimulus-specific habituation (non-associative learning). (5) The circuits suggested to underlie modulatory forebrain functions are accentuated in standard schemes of the neural macronetwork. These provide concepts suitable for future decisive experiments.

The biopharmaceutical aspects of nasal mucoadhesive drug delivery

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

Scintigraphic evaluation in rabbits of nasal drug delivery systems based on carbopol 971p((R)) and carboxymethylcellulose

The residence time of apomorphine mucoadhesive preparations incorporating 99mTc labeled colloidal albumin in rabbit nasal cavity was evaluated by gamma scintigraphy. This technique was used to compare the nasal clearance of preparations based either on Carbopol 971P((R)) or lactose (control), each with and without apomorphine, or carboxymethylcellulose with apomorphine. The planar 1-min images showed an excipient-dependent progressive migration of radioactivity with time from the nasal cavity to the stomach and intestine. Thirty minutes post insufflation, the percentages of the formulations cleared from the nasal cavity were 47% for lactose, 26% for lactose/apomorphine, 10% for Carbopol 971P((R)), and 3% for both Carbopol 971P((R))/apomorphine and carboxymethylcellulose/apomorphine. Three hours post insufflation, the percentages of the formulations cleared from the nasal cavity were 70% for lactose, 58% for lactose/apomorphine, 24% for Carbopol 971P((R)), 12% for Carbopol 971P((R))/apomorphine, and 27% for carboxymethylcellulose/apomorphine. Apomorphine inhibited nasal mucociliary clearance since migration of the radioactivity administered with apomorphine containing preparations was in all cases slower than that of the corresponding powder without apomorphine. The peak plasma concentration of apomorphine was attained while all the formulations were still within the nasal cavity. The use of mucoadhesive polymers such as Carbopol 971P((R)) or carboxymethylcellulose in nasal dosage forms increases their residence time within the nasal cavity and provides the opportunity for sustained nasal drug delivery.

Nasal toxicological investigations of Carbopol 971P formulation of apomorphine: effects on ciliary beat frequency of human nasal primary cell culture and in vivo on rabbit nasal mucosa

OBJECTIVE

The objective of this study was to investigate the nasal toxicity of a mucoadhesive Carbopol 971P formulation of apomorphine.

MATERIALS AND METHODS

The effects of different concentrations of Carbopol 971P and apomorphine on ciliary beat frequency (CBF) were studied in suspension cultures of human nasal epithelial cells. The rabbit nasal mucosal tolerance of the formulation and its components were investigated using light microscopy. Different groups of the rabbits received twice daily, air puffs, glucose, glucose/apomorphine, Carbopol 971P or Carbopol 971P/apomorphine for 1 week (glucose-treated rabbits) or 1, 2 and 4 weeks (other treatments).

RESULTS

Both Carbopol 971P and apomorphine showed both concentration- and time-dependent inhibitory effects on the CBF. The effects on CBF were: apomorphine, 1.0% w/v, irreversible ciliostasis; 0.1 and 0.5% w/v, reversible cilio-inhibition; 0.01%w/v, irreversible cilio-stimulation; and Carbopol 971P, 0.1 and 0.25% w/v, partially-reversible cilio-inhibition. Glucose and glucose/apomorphine physical mixture caused mild inflammation. Carbopol 971P (both with and without apomorphine) caused severe inflammation, which increased with duration of treatment. Necrosis, squamous metaplasia or ciliary degeneration was not observed.

CONCLUSIONS

Due to the severe inflammation caused by Carbopol 971P with and without apomorphine, we conclude that this polymer is not a suitable carrier for intranasal administration of apomorphine. This is in spite of the reversible effects of Carbopol 971P (0.1 and 0. 25% w/v) and apomorphine (0.1 and 0.5% w/v) on CBF.