Intranasal administration of peptides: nasal deposition, biological response, and absorption of desmopressin

Challenges and innovations of drug delivery in older age

Both drug delivery performance and various age-related physical, mental and physiological changes can affect drug effectiveness and safety in elderly patients. The many drug delivery systems developed over the years include recent novel transdermal, nasal, pulmonary and orally disintegrating tablets that provide consistent, precise, timely and more targeted drug delivery. Certain drug delivery systems may be associated with suboptimal outcomes in the elderly because of the nature of drug present, a lack of appreciation of the impact of age-related changes in drug absorption, distribution and clearance, the limited availability of pharmacokinetic, safety and clinical data. Polypharmacy, patient morbidity and poor adherence can also contribute to sub-optimal drug delivery systems outcomes in the elderly. The development of drug delivery systems for the elderly is a poorly realised opportunity, with each system having specific advantages and limitations. A key challenge is to provide the innovation that best meets the specific physiological, psychological and multiple drug requirements of individual elderly patients.

Overview of intranasally delivered peptides: key considerations for pharmaceutical development

INTRODUCTION

Intranasal (IN) delivery for peptides provides unique advantages compared to other invasive systemic delivery routes. However, there still lacks a clear understanding on how to evaluate the potential of the peptides for nasal delivery and key considerations for the nasal formulation development.

AREAS COVERED

A retrospective analysis of intranasally delivered peptides was conducted. The goals of this undertaking were 1) to build a database of the key physicochemical and pharmacokinetic properties of peptides delivered by the nasal route, 2) to evaluate formulation attributes applied to IN peptide delivery systems, and 3) to provide key considerations for IN delivery of peptides.

EXPERT OPINION/COMMENTARY

Extensive data mining showed that peptides with molecular weights up to 6000 Da have been delivered intranasally. The high solubility of some peptides highlighted the possibility of delivering sufficient amounts of peptide in the limited volume available for nasal sprays. Permeation enhancers and mucoadhesives have shown promise in improving the IN bioavailability of peptides. Other formulation considerations, such as the type of formulation, pH, osmolality, as well as drug deposition, are reviewed herein. Based on this retrospective analysis, key considerations for nasal peptides formulations were proposed to guide drug discovery and development for IN delivery of peptides.

Challenges in nasal drug absorption: how far have we come?

The nasal route is commonly used for local delivery of drugs to treat inflammatory conditions. It is also an attractive route for systemic delivery of some drugs. Irrespective of intended use, administered drugs must permeate the epithelial or olfactory membrane to be effective. The enthusiasm for potential use of the nasal route for systemic drug delivery has not been met by comparable success. In this paper, the anatomical and physiological attributes of the nasal cavity and paranasal sinuses important for drug delivery and challenges limiting drug absorption are discussed. Efforts made so far in improving nasal drug absorption such as overcoming restrictive nasal geometry and paranasal sinuses accessibility, mucociliary clearance, absorption barriers, metabolism and drug physicochemical challenges are discussed. Highlights on future prospects of nasal drug delivery/absorption were discussed.

Nose-to-brain delivery of insulin enhanced by a nanogel carrier

Recent evidences suggest that insulin delivery to the brain can be an important pharmacological therapy for some neurodegenerative pathologies, including Alzheimer disease (AD). Due to the presence of the Blood Brain Barrier, a suitable carrier and an appropriate route of administration are required to increase the efficacy and safety of the treatment. Here, poly(N-vinyl pyrrolidone)-based nanogels (NG), synthetized by e-beam irradiation, alone and with covalently attached insulin (NG-In) were characterized for biocompatibility and brain delivery features in a mouse model. Preliminarily, the biodistribution of the "empty" nanocarrier after intraperitoneal (i.p.) injection was investigated by using a fluorescent-labeled NG. By fluorescence spectroscopy, SEM and dynamic light scattering analyses we established that urine clearance occurs in 24h. Histological liver and kidneys inspections indicated that no morphological alterations of tissues occurred and no immunological response was activated after NG injection. Furthermore, after administration of the insulin-conjugated nanogels (NG-In) through the intranasal route (i.n.) no alteration or immunogenic response of the nasal mucosa was observed, suggesting that the formulation is well tolerated in mouse. Moreover, an enhancement of NG-In delivery to the different brain areas and of its biological activity, measured as Akt activation levels, with reference to free insulin administration was demonstrated. Taken together, these results indicate that the synthesized NG-In enhances brain insulin delivery upon i.n. administration and strongly encourage its further evaluation as therapeutic agent against some neurodegenerative diseases.

Desmopressin (DDAVP), tranexamic acid and haemostasis

Desmopressin is a widely used haemostatic drug. In contrast to vasopressin, it has no pressor activity. The effect is immediate, with two to six-fold increases in the plasma concentrations of coagulation factor VIII, von Willebrand factor and tissue plasminogen activator, and of platelet adhesiveness. Desmopressin is used in patients with mild haemophilia A, von Willebrand's disease, congenital platelet dysfunction or acquired platelet dysfunction due to uraemia or such drugs as aspirin. Tranexamic acid is an antifibrinolytic agent effective against menorrhagia, epistaxis and bleeding after conization or oral surgery; its haemostatic effect in connection with major surgery is presently being evaluated.

Nanotechnology for CNS delivery of bio-therapeutic agents

The current therapeutic strategies are not efficient in treating disorders related to the central nervous system (CNS) and have only shown partial alleviation of symptoms, as opposed to, disease modifying effects. With change in population demographics, the incidence of CNS disorders, especially neurodegenerative diseases, is expected to rise dramatically. Current treatment regimens are associated with severe side-effects, especially given that most of these are chronic therapies and involve elderly population. In this review, we highlight the challenges and opportunities in delivering newer and more effective bio-therapeutic agents for the treatment of CNS disorders. Bio-therapeutics like proteins, peptides, monoclonal antibodies, growth factors, and nucleic acids are thought to have a profound effect on halting the progression of neurodegenerative disorders and also provide a unique function of restoring damaged cells. We provide a review of the nano-sized formulation-based drug delivery systems and alternate modes of delivery, like the intranasal route, to carry bio-therapeutics effectively to the brain.

Current understanding of nasal morphology and physiology as a drug delivery target

The nasal cavity is both a target for locally and systemically acting medications. An adequate treatment for rhinosinusitis continues to be an unmet need. With the recent approval of intranasal medications for the treatment of pain, the nasal cavity continues to be a viable route for rapid uptake into the systemic circulation. Despite the opportunities, there is still a void in the knowledge of how therapeutic entities interact with the nasal epithelium. In addition, new opportunities in mucosal immunity via nasal vaccination as well as the elusive nose to brain uptake continue to drive innovation. To facilitate understanding of the issues involved that facilitate drug delivery in the nose, a review of nasal morphology and physiology is presented.

Nasal drug delivery devices: characteristics and performance in a clinical perspective-a review

Nasal delivery is the logical choice for topical treatment of local diseases in the nose and paranasal sinuses such as allergic and non-allergic rhinitis and sinusitis. The nose is also considered an attractive route for needle-free vaccination and for systemic drug delivery, especially when rapid absorption and effect are desired. In addition, nasal delivery may help address issues related to poor bioavailability, slow absorption, drug degradation, and adverse events in the gastrointestinal tract and avoids the first-pass metabolism in the liver. However, when considering nasal delivery devices and mechanisms, it is important to keep in mind that the prime purpose of the nasal airway is to protect the delicate lungs from hazardous exposures, not to serve as a delivery route for drugs and vaccines. The narrow nasal valve and the complex convoluted nasal geometry with its dynamic cyclic physiological changes provide efficient filtration and conditioning of the inspired air, enhance olfaction, and optimize gas exchange and fluid retention during exhalation. However, the potential hurdles these functional features impose on efficient nasal drug delivery are often ignored. With this background, the advantages and limitations of existing and emerging nasal delivery devices and dispersion technologies are reviewed with focus on their clinical performance. The role and limitations of the in vitro testing in the FDA guidance for nasal spray pumps and pressurized aerosols (pressurized metered-dose inhalers) with local action are discussed. Moreover, the predictive value and clinical utility of nasal cast studies and computer simulations of nasal airflow and deposition with computer fluid dynamics software are briefly discussed. New and emerging delivery technologies and devices with emphasis on Bi-Directional™ delivery, a novel concept for nasal delivery that can be adapted to a variety of dispersion technologies, are described in more depth.

Drug development of intranasally delivered peptides

Intranasal drug delivery has attracted increasing attention as a noninvasive route of administration for therapeutic proteins and peptides. The delivery of therapeutic peptides through the nasal route provides an alternative to intravenous or subcutaneous injections. This review highlights the drug-development considerations unique to nasal therapeutics and discusses some of the factors and strategies that affect and can improve nasal absorption of peptides. The selectivity and good safety profile typical of peptide therapeutics, along with the dose limitation for intranasal administration, can provide challenges in drug development. Therefore, nasal peptide therapeutics often require special considerations in the nonclinical safety evaluations, such as determining drug exposure in the context of the maximum feasible dose in order to adequately prepare nasal products for clinical studies.

Bioavailability of a novel midazolam gel after intranasal administration in dogs

OBJECTIVE

To compare the pharmacokinetics of a novel bioadhesive gel formulation of midazolam after intranasal (IN) administration with that of midazolam solution after IN, IV, and rectal administration to dogs.

ANIMALS

10 (5 males and 5 females) healthy adult Beagles.

PROCEDURES

Dogs were assigned to 4 treatment groups for a crossover study design. Initially, midazolam solution (5 mg/mL) was administered (0.2 mg/kg) IV to group 1, rectally to group 2, and IN to group 3; a 0.4% hydroxypropyl methylcellulose midazolam gel formulation (50 mg/mL) was administered (0.2 mg/kg, IN) to group 4. Each dog received all 4 treatments; there was a 7-day washout period between subsequent treatments. Blood samples were collected before and after midazolam administration. Plasma concentration of midazolam was determined by use of high-performance liquid chromatography.

RESULTS

The peak plasma concentration after IN administration of the gel formulation was significantly higher than that after IN and rectal administration of the solution. Mean ± SD time to peak concentration was 11.70 ± 2.63 minutes (gel IN), 17.50 ± 2.64 minutes (solution IN), and 39 ± 14.49 minutes (solution rectally). Mean bioavailability of midazolam was 70.4% (gel IN), 52.0% (solution IN), and 49.0% (solution rectally). Bioavailability after IN administration of the gel formulation was significantly higher than that after IN and rectal administration of the solution.

CONCLUSIONS AND CLINICAL RELEVANCE

IN administration of midazolam gel was superior to both IN and rectal administration of midazolam solution with respect to peak plasma concentration and bioavailability.

Drug delivery strategies for Alzheimer's disease treatment

INTRODUCTION

Current Alzheimer's disease (AD) therapy is based on the administration of the drugs donepezil, galantamine, rivastigmine and memantine. Until disease-modifying therapies become available, further research is needed to develop new drug delivery strategies to ensure ease of administration and treatment persistence.

AREAS COVERED

In addition to the conventional oral formulations, a variety of drug delivery strategies applied to the treatment of AD are reviewed in this paper, with a focus on strategies leading to simplified dosage regimens and to providing new pharmacological tools. Alternatives include extended release, orally disintegrating or sublingual formulations, intranasal or short- and long-acting intramuscular or transdermal forms, and nanotechnology-based delivery systems.

EXPERT OPINION

The advent of new research on molecular mechanisms of AD pathogenesis has outlined new strategies for therapeutic intervention; these include the stimulation of α-secretase cleavage, the inhibition of γ-secretase activity, the use of non-steroidal anti-inflammatory drugs, neuroprotection based on antioxidant therapy, the use of estrogens, NO synthetase inhibitors, and natural agents such as polyphenols. Unfortunately, these compounds might not help patients with end stage AD, but might hopefully slow or stop the disease process in its early stage. Nanotechnologies may prove to be a promising contribution in future AD drug delivery strategies, in particular drug carrier nano- or microsystems, which can limit the side effects of anti-Alzheimer drugs.

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.

The effect of functional endoscopic sinus surgery on nasal spray distribution to the middle meatus in patients with rhinosinusitis

BACKGROUND

Because the principle behind functional endoscopic sinus surgery (FESS) recognizes the middle meatus as essential for the control of the disease, the effect of the operation in the distribution of drugs in the same area should be of similar importance. This study was designed to clarify whether nasal drug delivery is improved in patients after FESS. The study involved a prospective assessment within subject comparison. The subjects were 20 adult (>18 years old) patients on the waiting list for FESS. It was conducted within two teaching hospitals in the East of Scotland.

METHODS

A novel method was used, positioning a neurosurgical patty in the middle meatus and assessing blue dye nasal spray absorption on a 4-point scale.

RESULTS

A significant improvement was observed in the distribution of the indicator in the middle meatus postoperatively. Seventy percent of the patients showed improvement in the drug distribution after FESS. The median result for absorption score was 2 preoperatively (<50%) and 3 postoperatively (>50%). The difference was statistically significant (p<0.001).

CONCLUSION

The distribution of nasal drugs is improved in the middle meatus after FESS. This can have important clinical applications that can benefit patients in otolaryngology as well as other disciplines.

Direct transport of VEGF from the nasal cavity to brain

The aim of the present study was to assess the potential of delivering VEGF directly into the central nervous system (CNS) following intranasal administration. Adult Sprague-Dawley rats were randomized into two groups, given [(125)I]-VEGF intranasally or intravenously. VEGF was intranasally administered in both nares alternately, the single dose is 10 microl with time interval of 2 min for about 18.5 min. The intravenous (IV) group was treated with 100 microl [(125)I]-VEGF intravenously. Thirty minutes after administration, rats were killed following blood sample collections, then the brains were removed, and olfactory bulb, striatum corpora, cortex, thalamus, pons, cerebella, medulla, hippocampus, cervical cord and other tissues were collected, weighted, under auto gamma counting and autoradiography analysis. Cisternal sampling of cerebrospinal fluid (CSF) was performed in an additional group of animals. Both gamma counting and high resolution phosphor imaging of tissue sections showed that intranasal administration of [(125)I]-VEGF resulted in substantial delivery throughout the CNS. The highest CNS tissue concentration following IN delivery was found in the trigeminal nerve, followed by the optic nerve, olfactory bulbs, olfactory tubercle, striatum, medulla, frontal cortex, midbrain, pons, appendix cerebri, thalamus, hippocampus, cerebellum. Intranasal administration of [(125)I]-VEGF also targeted the deep cervical lymph nodes. CSF did not contain [(125)I]-VEGF following intranasal administration. Intravenous [(125)I]-VEGF resulted in blood and peripheral tissue exposure higher concentrations than that intranasal administration, but CNS concentrations were significantly lower. The results suggest intranasally delivered VEGF can bypass the blood-brain barrier via olfactory- and trigeminal-associated extracellular pathways to directly entry into the CNS. Intranasal administration of VEGF may provide an effective way for the treatments of CNS diseases.

Distribution and clearance of bioadhesive formulations from the olfactory region in man: Effect of polymer type and nasal delivery device

There is an increasing need to identify novel approaches by which to improve the efficiency of drug transport from the nasal cavity (olfactory region) to the CNS, especially for treatment of central nervous system disorders. It is suggested, that one approach is the combination of active targeting of a bioadhesive formulation, that will retain the drug at the absorption site, potentially in combination with, an absorption enhancer. Two low methylated pectins, LM-5 and LM-12 were selected for evaluation as drug delivery systems, due to their ability to gel in the nasal cavity and their bioadhesive characteristics, together with chitosan G210, which acts both as a bioadhesive material and as an efficient absorption enhancer. It was found that all of the bioadhesive formulations were able to reach the olfactory region in the nasal cavity of human volunteers when delivered using a simple nasal drop device. Furthermore, the formulations displayed a significantly increased residence time on the epithelial surface. This was in contrast to a non-bioadhesive control delivered with the same device. In contrast, a pectin formulation administered with a nasal spray system did not show an increase in residence time in the olfactory region. It was further shown that the reproducibility of olfactory delivery of a polymer formulation was significantly better intra-subject than inter-subject.

Validity of in vitro tests on aqueous spray pumps as surrogates for nasal deposition, absorption, and biologic response

This research investigated the impact of the full range of in vitro spray characterization tests described in the FDA Draft Bioequivalence Guidance on nasal deposition pattern, pharmacokinetics, and biological response to nicotine administered by two aqueous nasal spray pumps in human volunteers. Nicotine was selected as a model drug (even though it is not locally acting) based on its ability to alter cardiac function and available plasma assay. Significant differences in pump performance-including mean volume diameters, spray angle, spray width, and ovality ratios-were observed between the two pumps. There were no significant differences in deposition pattern, or pharmacokinetic or pharmacodynamic response to the nasally administered nicotine. Although there were statistical differences in the in vitro tests between the two pumps, these differences did not result in significant alterations in the site of droplet deposition within the nose, the rate and extent of nicotine absorption, or the physiologic response it induced. These results suggest that current measures of in vitro performance, particularly spray angle and spray pattern (ovality), may not be clinically relevant. Additional research is needed to define what spray pump characteristics are likely to produce differences in deposition pattern and drug response.

Intranasal deposition of nebulized saline: a radionuclide distribution study

BACKGROUND

Despite the popularity of various nasal sprays and nebulizers, there are limited data regarding the anatomic distribution of particles generated by these devices. This pilot study sought to characterize distribution patterns of nebulized and sprayed saline particles in normal subjects and postsurgical sinus patients.

METHODS

Fifteen subjects were studied in three trials: metered-dose nasal spray bottle versus vortex-propelled nebulizer in normal subjects, passive-diffusion nebulizer versus vortex nebulizer in normal subjects, and passive nebulizer versus vortex nebulizer in postsurgical sinus patients. Radiolabeled saline was administered, and nose, lungs, and stomach were imaged. Images were scored by four blinded reviewers for degree of penetration at nine anatomic subsites.

RESULTS

Compared with spray bottle, the vortex nebulizer showed more focal intranasal distribution with reduced nasopharyngeal, pharyngeal, and gastric penetration in normal subjects. Three of five subjects showed probable frontal sinus penetration by vortex nebulizer, but no other sinus penetration was noted. No patients showed sinus penetration with the spray bottle. In a separate trial against the passive nebulizer, the vortex nebulizer again showed a greater tendency for sinus penetration in normal subjects, with three of five showing some degree of sphenoid penetration and one of five showing slight maxillary penetration. In contrast, no sinus penetration was observed with the passive nebulizer. In the postsurgical patient cohort, minimal sinus penetration was noted with either the vortex nebulizer or the passive nebulizer. Despite surgically patent sinuses, only one of five subjects showed any type of sinus penetration.

CONCLUSION

The nebulizer and nasal spray devices tested in general showed limited penetration of the sinuses in both normal and postoperative patients. The device showing greatest promise for sinus penetration in normal patients was the vortex nebulizer, with an overall penetration rate in normal patients of 30% in the frontal, 30% in the sphenoid, and 10% in the maxillary. Understanding delivery patterns of topical therapies may be important in evaluating the efficacy of various topical treatment modalities.

Delivery of 125I-cobrotoxin after intranasal administration to the brain: a microdialysis study in freely moving rats

In order to determine the contribution of intranasal (i.n.) administration to the uptake of large molecular weight (MW) substances into central nervous system (CNS), concentration in brain of the centrally acting polypeptide cobrotoxin (NT-I) versus time profiles were studied using dual-probe microdialysis in awake free-moving rats. NT-I, radiolabeled with sodium (125)I-Iodide ((125)I-NT-I), was administered at the dose of 105 microg/kg intravenously and intranasally in the same set of rat (n=15). The (125)I-NT-Inasal preparations were formulated with borneol/menthol eutectic mixture (+BMEM) as an absorption enhancer and without (-BMEM). After application, the dialysates sampled simultaneously from olfactory bulb and cerebellar nuclei were measured in a gamma-counter for radioactivity. The real concentrations of NT-I were recalculated by in vivo recoveries of microdialysis probes. The results showed that the area under the curve (AUC) value in cerebellar nuclei (2283.51+/-34.54 min ng/ml) following i.n. administration (+BMEM) was significantly larger than those (AUC(olfactory)=1141.92+/-26.42 min ng/ml; AUC(cerebellar)=1364.62+/-19.35 min ng/ml) after intravenous (i.v.) bolus, respectively. A prolonged time values to peak concentrations after i.n. application (+BMEM) were observed compared with those following i.v. administration. Also, following i.n. application (+BMEM) the measured time value to peak concentration in cerebellar nuclei (85 min) was statistically longer than that in olfactory bulb (75 min), which could be plausibly an indication for NT-I delivery into brain via nose-brain pathway in the presence of absorption enhancer. i.n. administration (-BMEM) had little or no ability of NT-I delivering into brain. In conclusion, i.n. administration (+BMEM) significantly enhanced brain transport of NT-I with uneven distribution in discrete regions of brain compared with i.v. administration. Additionally, multi-probe microdialysis technique should be considerably valuable in brain delivery studies.

Desmopressin Toxicity Due to Prolonged Half-Life in 18 Patients With Nocturnal Enuresis

PURPOSE

Desmopressin has been used extensively for primary nocturnal enuresis and it is associated with a low incidence of adverse effects. The only reported serious side effect is seizure or altered levels of consciousness resulting from water intoxication, which has been reported for the nasal spray. We describe 18 children with clinical symptoms of water intoxication due to the prolonged bioactivity of desmopressin nasal spray.

MATERIALS AND METHODS

We evaluated 18 patients with clinical suspicion of prolonged desmopressin bioactivity during treatment with intranasal desmopressin for primary nocturnal enuresis. The control group consisted of 50 children with primary nocturnal enuresis and proven nocturnal polyuria who were treated with the same desmopressin regimen.

RESULTS

All patients had prolonged maximal urinary concentration capacity and delayed restoration of daytime diluting capacity (p <0.01). Of the patients 15 had the characteristic clinical symptoms of water intoxication with vomiting, headache, decreased consciousness and hyponatremia. We suspect that these symptoms are secondary to prolonged desmopressin bioactivity.

CONCLUSIONS

Prolonged desmopressin bioactivity may increase the risk of water intoxication.

Influence of deposition and spray pattern of nasal powders on insulin bioavailability

The influence of the deposition pattern and spray characteristics of nasal powder formulations on the insulin bioavailability was investigated in rabbits. The formulations were prepared by freeze drying a dispersion containing a physical mixture of drum dried waxy maize starch (DDWM)/Carbopol 974P (90/10, w/w) or a spray-dried mixture of Amioca starch/Carbopol 974P (25/75, w/w). The deposition in the nasal cavity of rabbits and in a silicone human nose model after actuation of three nasal delivery devices (Monopowder, Pfeiffer and experimental system) was compared and related to the insulin bioavailability. Posterior deposition of the powder formulation in the nasal cavity lowered the insulin bioavailability. To study the spray pattern, the shape and cross-section of the emitted powder cloud were analysed. It was concluded that the powder bulk density of the formulation influenced the spray pattern. Consequently, powders of different bulk density were prepared by changing the solid fraction of the freeze dried dispersion and by changing the freezing rate during freeze drying. After nasal delivery of these powder formulations no influence of the powder bulk density and of the spray pattern on the insulin bioavailability was observed.

New approach of the treatment of von Willebrand’s disease during pregnancy

AIM

The aim of the study was to analyze the effectiveness of the application of DDAVP (desmopressin) and Hemate P with cryoprecipitate pre- and postpartum in patients with von Willebrand disease.

METHODS

We monitored 32 patients with von Willebrand disease during the study period 1993-2003. DDAVP was applied in the 36th/37th week of gestation and cryoprecipitate and fresh frozen plasma were applied 1 day before and 3 days after delivery. DDAVP treatment continued for 4 weeks. Factor VIII (Hemate P) at the day of delivery

RESULTS

No complications occurred in the studied population.

CONCLUSION

Precipitation of DDAVP, Hemate P, and cryoprecipitate may help in the treatment of pregnant women with von Willebrand disease.

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.

Intranasal administration of melatonin starch microspheres

Using melatonin as model drug, starch microspheres for intranasal administration were prepared by an emulsification-crosslinking technique using a uniform design to optimize preparation conditions. The entrapment ratio of melatonin in the microspheres was 11.0% and particle sizes ranged from 30 to 60 microm. Melatonin was released from the microspheres in a sustained manner in vitro. Nasal clearance of 99mTC labeled starch microspheres was investigated using gamma scintigraphy. It was revealed that >80% of the starch microspheres could be detected in the nasal tissue 2h after administration, compared to 30% for a solution. The pharmacokinetics of melatonin starch microspheres was investigated after intranasal administration. The absorption rate was rapid (T(max) min), and the absolute bioavailability was high, 84.07%. A good correlation was found between in vitro release and in vivo absorption data.

LC–MS determination of desmopressin acetate in human skin samples

A sensitive, selective and accurate high-performance liquid chromatography-mass spectroscopy (LC-MS) assay for the determination of desmopressin acetate (1-deamino-8-D-arginine vasopressin, DDAVP) from human skin samples was developed and validated. Pieces of human breast skin were impregnated with DDAVP solutions and DDAVP was extracted with an optimum extraction procedure. The extracted solutions were then analyzed by a LC system, comprising of a Nucleosil C18 column (CC 125/2, 120-3) and a mobile phase of 0.01% formic acid in a mixture of 1.6 mM ammonium acetate and acetonitrile (33:67, v/v), coupled with electrospray ionization mass spectrometry (ESI-MS). Satisfactory results were obtained with limits of detection and quantification as low as 10 and 40 ng/ml, respectively, and with very good intra- and inter-day repeatability.

Nasal drug delivery--possibilities, problems and solutions

This paper discusses the problems associated with nasal drug delivery and how it is possible, sometimes by means of quite simple concepts, to improve transport across the nasal membrane. In this way it is feasible to deliver efficiently challenging drugs such as small polar molecules, peptides and proteins and even the large proteins and polysaccharides used in vaccines or DNA plasmids exploited for DNA vaccines. The transport of drugs from the nasal cavity directly to the brain is also described and examples of studies in man, where this has been shown to be feasible, are discussed. Recent results from Phase I/II studies in man with a novel nasal chitosan vaccine delivery system are also described. Finally, the author's thoughts about the future for nasal drug delivery are also depicted.

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.

Validity of in vitro tests on aqueous spray pumps as surrogates for nasal deposition

PURPOSE

To determine whether deposition pattern is related to in vitro measurements of droplet size, plume geometry, and spray pattern between two different nasal spray pumps believed to have different performance characteristics.

METHODS

Ten healthy volunteers inhaled radiolabeled saline from two different spray pumps (pump A and pump B). Deposition pattern was quantified from lateral views of the nose by gamma scintigraphy, expressed as the ratio of anterior to posterior (I:O) and superior to inferior (U:L) deposition. Droplet size was determined by Malvern Mastersizer S. Spray patterns were determined at 2.5 and 5 cm from the tip of the spray nozzle. Two-dimensional images of the emitted plume were captured by high-speed still photography.

RESULTS

There were no significant differences in I:O or U:L ratios for pump A compared to pump B, indicating no significant differences in deposition pattern. The volume diameters, Dv10 and Dv50, were not statistically different for pump A compared to pump B. There was a significant difference in Dv90 between pump A and pump B, (86.9 +/- 5.8 microm and 77.4 +/- 2.4 microm. respectively; P < 0.001). The ratio of the longest to shortest diameter for the spray pattern with pump A was 1.26 +/- 0.06 at 2.5 cm and 1.44 +/- 0.08 at 5 cm. The ratio for pump B was 1.13 +/- 0.03 at 2.5 cm and 1.19 +/- 0.05 at 5 cm. Ratios at both heights were statistically different for pump A compared to pump B (P < 0.00002 and P < 0.000001, respectively) Plume geometry analysis indicated statistical differences in both the width (17.0 +/- 0.97 vs. 18.5 +/- 0.56 cm, respectively: p<0.001) and the maximum length of the plumes (46.0 +/- 1.83 vs. 53.1 +/- 4.88 cm, respectively; p < .002). The differences in velocity of the plume and spray angle between the two pumps were not statistically different. CONCLUSIONS. Certain in vitro tests detected performance differences between the two pumps. However, these differences did not translate into different deposition patterns in vivo.

Clearance characteristics of chitosan based formulations in the sheep nasal cavity

This paper describes the clearance characteristics of two bioadhesive nasal delivery systems in the form of chitosan microspheres and chitosan solution, from the nasal cavity of conscious sheep. The pattern of deposition and clearance of the nasal dosage forms were evaluated using a radioactive tracer and the non-invasive technique of gamma scintigraphy. The clearance of chitosan microsphere and solution formulations was compared with that of a control solution. The data show that the control was cleared rapidly from the sheep nasal cavity with a half-time of clearance (time taken for 50% clearance; t(50%)) of about 15 min. The bioadhesive chitosan delivery systems were cleared at a slower rate, with half-times of clearance of 43 min and 115 min, for solution and microsphere formulations respectively. From the results reported in this study it can be concluded that the chitosan delivery systems investigated had significantly reduced rates of clearance from the sheep nasal cavity, as compared to the control. Consequently, chitosan delivery systems have the ability to increase the residence time of drug formulations in the nasal cavity thereby providing the potential for improved systemic medication. The nasal clearance rates recorded in the sheep model mimic very closely the clearance rates found in a previous study using human subjects. It can also be concluded that the sheep can be considered a suitable model for in vivo nasal clearance studies of novel bioadhesive drug delivery systems.

Preparation of desmopressin-containing liposomes for intranasal delivery

The loading and leakage characteristics of the desmopressin-containing liposomes and the effect of liposomes on the nasal mucosa permeation and antidiuresis of desmopressin were investigated. Higher loading efficiency of desmopressin for positively charged liposomes than negatively charged liposomes was obtained, and neutral liposomes resulted in a similar loading efficiency as that of positively charged liposomes. Greater leakage of desmopressin from negatively charged liposomes than from positively charged and neutral liposomes was shown. The increase of permeability of desmopressin through the nasal mucosa indicated positively charged liposomes>negatively charged liposomes>solution. It was suggested that the enhanced contact time of positively charged liposomes with negatively charged nasal mucosa led to a high local desmopressin concentration on the penetration site to promote an effective penetration of desmopressin through the nasal mucosa. The desmopressin antidiuresis result after intranasal administration was in good agreement with the permeability result in the order of positively charged liposomes>negatively charged liposomes>solution. One of the mechanisms for the explanation of the best result on the enhancement of antidiuresis for positively charged liposomes may be the bioadhesive effect of the liposomes on the negatively charged nasal mucosa.

The effect of the nasal cycle on mucociliary clearance

The nasal cycle is a well-recognised physiological phenomenon where each side of the nose alternates through phases of congestion and decongestion. Although many physiological properties of the nose alternate with the nasal cycle whether this has any effect on the nasal mucociliary clearance is less clear. As the nose is a potential site for the administration of pharmaceuticals, it is essential that any factors that could affect clearance (and hence absorption) are identified. This study set out to investigate if mucociliary clearance rates differed between the clear and obstructed airway at a morning peak of the nasal cycle in five healthy volunteers with normal nasal anatomy using a dual-radioisotope labelling procedure that allows both sides of the nose to be assessed simultaneously. The clearance of the radiopharmaceutical formulations from the nasal cavity was monitored using gamma scintigraphy and decay-adjusted 50%-clearance times were calculated for each nostril. The ratios of clearance times from the patent nostril when compared to the obstructed nostril were statistically significant (two-tailed t-test; P = 0.039), the mean ratio being 2.5 : 1 (SEM +/- 0.5). It can be concluded that the nasal cycle has a marked effect on the mucociliary clearance patterns of the nose. This may have both theoretical and practical implications for the nasal delivery of drugs.

Improved nasal bioavailability of FITC-dextran (Mw 4300) from mucoadhesive microspheres in rabbits

The nasal bioavailability of fluorescein isothiocyanate-dextran (FITC-dextran) (Mw = 4300) encapsulated in non-mucoadhesive and mucoadhesive microspheres in New Zealand White rabbits was investigated. FITC-dextran was administered nasally encapsulated in carbopol 934P, chitosan and lactose microspheres and the bioavailability compared to intravenous administration of FITC-dextran solution. Administration of FITC-dextran as carbopol microspheres produced a significantly greater bioavailability (33%) than after administration as chitosan (13%) and non-mucoadhesive rapidly dissolving control lactose microspheres (9%). The FITC-dextran terminal plasma half-lives after carbopol 934P and chitosan microsphere administration were significantly longer than after intravenous administration of FITC-dextran. The FITC-dextran terminal plasma half-life after carbopol 934P microspheres administration was significantly longer than after lactose microsphere administration. This data suggested that the increase in FITC-dextran bioavailability after carbopol 934P microspheres administration was due to increased residence at the absorptive site via mucoadhesion and reduced mucociliary clearance. A change in mucosal permeability could not however be discounted especially for the chitosan microspheres.

Dose-related efficacy and tolerability of fluticasone propionate nasal drops 400 microg once daily and twice daily in the treatment of bilateral nasal polyposis: a placebo-controlled randomized study in adult patients

BACKGROUND

Topical corticosteroids are the accepted medical adjunct to surgery in patients suffering from nasal polyposis. Fluticasone propionate (FP) is a potent, topically active corticosteroid which has been formulated as nasal drops specifically for the treatment of polyposis.

OBJECTIVES

To evaluate dose-related efficacy and tolerability of FP nasal drops (FPND) in the treatment of mild to moderate bilateral polyposis; in a double-blind, placebo-controlled, multicentre international study.

METHODS

Adult patients (n = 142) with bilateral nasal polyps were randomized to receive either FPND 400 microg once daily (o.d.), FPND 400 microg twice daily (b.i.d.) or placebo for 12 weeks. The majority then entered a further 12 week open period during which all patients received FPND 400 microg o.d. The primary efficacy endpoint was the physicians' visual assessment of polyp size. Secondary clinical endpoints were nasal blockage and overall rhinitis (0-3 scores), peak nasal inspiratory flow (PNIF), olfactory function tests, and requirement for polypectomy. The patients also kept twice daily records of symptom scores, peak nasal inspiratory flow (PNIF) and use of rescue medication.

RESULTS

At the end of the 12 week randomized treatment period, polyp size was reduced significantly by FPND 400 microg b.i.d. as compared with placebo (P = 0.006). Clinical assessments of nasal blockage and overall rhinitis showed significant improvements at several stages of treatment with both doses of FPND. Clinic PNIF was also improved significantly by both doses of FPND in comparison with placebo, and FPND 400 microg b.i.d. was significantly more effective than 400 microg o.d. (P = 0.045). Patient diary card scores supported the clinical assessments. Two patients on placebo required polypectomy and all treatments were well tolerated with a similar incidence of adverse events.

CONCLUSION

FPND 400 microg once or twice daily is an effective and well-tolerated treatment for bilateral nasal polyposis.

Intranasal insulin delivery and therapy

Intranasal insulin delivery has been widely investigated as an alternative to subcutaneous injection for the treatment of diabetes. The pharmacokinetic profile of intranasal insulin is similar to that obtained by intravenous injection and, in contrast to subcutaneous insulin delivery, bears close resemblance to the 'pulsatile' pattern of endogenous insulin secretion during meal-times. The literature suggests that intranasal insulin therapy has considerable potential for controlling post-prandial hyperglycaemia in the treatment of both IDDM and NIDDM. However, effective insulin absorption via the nasal route is unlikely without employing the help of absorption enhancers or promoters which are able to modulate nasal epithelial permeability to insulin and/or prolong the residence time of the drug formulation in the nasal cavity. This article discusses the structure and function of the nasal cavity, the barriers which prevent nasal insulin absorption and through the use of absorption enhancers or promoters methods by which these barriers may be overcome.

Intranasal drug delivery

In recent years the nasal route has received a great deal of attention as a convenient and reliable method for the systemic administration of drugs. Although this route is currently being marketed for the systemic administration of several drugs, it has only recently been studied. This chapter deals with animal techniques to study nasal absorption and the effect of physico-chemical and biopharmaceutical properties of drugs on the rate and extent of absorption. It also discusses factors affecting peptide absorption and methods to improve the nasal bioavailability of peptides. In the last part of the chapter the utility of the nasal route for the delivery of drugs to the brain is discussed.

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.