Nasal absorption of (S)-UH-301 and its transport into the cerebrospinal fluid of rats

Nanovesicular-Mediated Intranasal Drug Therapy for Neurodegenerative Disease

Numerous neurodegenerative conditions, such as Alzheimer's, Huntington's, Parkinson's, amyotrophic lateral sclerosis, and glioblastoma multiform are now becoming significant concerns of global health. Formulation-related issues, physiological and anatomical barriers, post-administration obstacles, physical challenges, regulatory limitations, environmental hurdles, and health and safety issues have all hindered successful delivery and effective outcomes despite a variety of treatment options. In the current review, we covered the intranasal route, an alternative strategic route targeting brain for improved delivery across the BBB. The trans-nasal pathway is non-invasive, directing therapeutics directly towards brain, circumventing the barrier and reducing peripheral exposure. The delivery of nanosized vesicles loaded with drugs was also covered in the review. Nanovesicle systems are organised in concentric bilayered lipid membranes separated with aqueous layers. These carriers surmount the disadvantages posed by intranasal delivery of rapid mucociliary clearance and enzymatic degradation, and enhance retention of drug to reach the site of target. In conclusion, the review covers in-depth conclusions on numerous aspects of formulation of drug-loaded vesicular system delivery across BBB, current marketed nasal devices, significant jeopardies, potential therapeutic aids, and current advancements followed by future perspectives.

Restoration of Adult Neurogenesis by Intranasal Administration of Gangliosides GD3 and GM1 in The Olfactory Bulb of A53T Alpha-Synuclein-Expressing Parkinson's-Disease Model Mice

Parkinson's disease (PD) is the second most common neurodegenerative disorder affecting the body and mind of millions of people in the world. As PD progresses, bradykinesia, rigidity, and tremor worsen. These motor symptoms are associated with the neurodegeneration of dopaminergic neurons in the substantia nigra. PD is also associated with non-motor symptoms, including loss of smell (hyposmia), sleep disturbances, depression, anxiety, and cognitive impairment. This broad spectrum of non-motor symptoms is in part due to olfactory and hippocampal dysfunctions. These non-motor functions are suggested to be linked with adult neurogenesis. We have reported that ganglioside GD3 is required to maintain the neural stem cell (NSC) pool in the subventricular zone (SVZ) of the lateral ventricles and the subgranular layer of the dentate gyrus (DG) in the hippocampus. In this study, we used nasal infusion of GD3 to restore impaired neurogenesis in A53T alpha-synuclein-expressing mice (A53T mice). Intriguingly, intranasal GD3 administration rescued the number of bromodeoxyuridine + (BrdU +)/Sox2 + NSCs in the SVZ. Furthermore, the administration of gangliosides GD3 and GM1 increases doublecortin (DCX)-expressing immature neurons in the olfactory bulb, and nasal ganglioside administration recovered the neuronal populations in the periglomerular layer of A53T mice. Given the relevance of decreased ganglioside on olfactory impairment, we discovered that GD3 has an essential role in olfactory functions. Our results demonstrated that intranasal GD3 infusion restored the self-renewal ability of the NSCs, and intranasal GM1 infusion promoted neurogenesis in the adult brain. Using a combination of GD3 and GM1 has the potential to slow down disease progression and rescue dysfunctional neurons in neurodegenerative brains.

Evaluation of Recent Intranasal Drug Delivery Systems to the Central Nervous System

Neurological diseases continue to increase in prevalence worldwide. Combined with the lack of modifiable risk factors or strongly efficacious therapies, these disorders pose a significant and growing burden on healthcare systems and societies. The development of neuroprotective or curative therapies is limited by a variety of factors, but none more than the highly selective blood-brain barrier. Intranasal administration can bypass this barrier completely and allow direct access to brain tissues, enabling a large number of potential new therapies ranging from bioactive peptides to stem cells. Current research indicates that merely administering simple solutions is inefficient and may limit therapeutic success. While many therapies can be delivered to some degree without carrier molecules or significant modification, a growing body of research has indicated several methods of improving the safety and efficacy of this administration route, such as nasal permeability enhancers, gelling agents, or nanocarrier formulations. This review shall discuss promising delivery systems and their role in expanding the clinical efficacy of this novel administration route. Optimization of intranasal administration will be crucial as novel therapies continue to be studied in clinical trials and approved to meet the growing demand for the treatment of patients with neurological diseases.

D-cycloserine nasal formulation development for anxiety disorders by using polymeric gels

D-cycloserine (DCS), a partial agonist at N-methyl-D-aspartate (NMDA) receptors, is used as an enhancer of exposure therapy for anxiety disorders. The purpose of the present study was to investigate the feasibility of using polymeric gels to increase the viscosity of the formulation and thereby increase the nasal residence time and sustained release of DCS in vitro. Hydroxypropyl methylcellulose (HPMC), hydroxypropyl cellulose (HPC), and methyl cellulose (MC) were prepared at concentrations of 0.5 to 5% w/v. Pluronic F-127 (PF-127) was prepared at concentrations of 15 to 35% w/v. pH, viscosity and in vitro DCS release behavior of the formulated gels were analyzed. All four gels that were tested, demonstrated sustained DCS release behavior over a 24-hour period, but with different rates. Based on the results of this study, HPMC, HPC, MC, and PF-127 are capable of increasing the viscosity of nasal gel formulations and of releasing DCS in sustained manner. Therefore, these polymeric gels can be suitable carriers for DCS nasal gel formulation.

Nose-to-brain transport pathways of wheat germ agglutinin conjugated PEG-PLA nanoparticles

PURPOSE

To investigate the possible pathways for transport of wheat germ agglutinin conjugated PEG-PLA nanoparticles (WGA-NP) into the brain after nasal administration.

METHODS

The nose-to-brain pathways were investigated using WGA-NP containing 6-coumarin (as a fluorescent marker) and (125)I-labeled WGA-NP. Ex vivo imaging analysis was also employed to visualize the transport process.

RESULTS

Nasal administration of WGA-NP to rats resulted in transcellular absorption across the olfactory epithelium and transfer to the olfactory bulb within 5 min. After entering the lamina propria, a proportion of WGA-NP were transferred from the olfactory nerve bundles and their surrounding connective tissue to the olfactory bulb. The trigeminal nerves also contributed to WGA-NP brain transfer, especially to WGA-NP distribution in the caudal brain areas. However, cerebrospinal fluid pathway may have little contribution to the process of transferring WGA-NP into the central nervous system (CNS) after intranasal administration.

CONCLUSIONS

These results demonstrated that intranasally administered WGA-NP reach the CNS via olfactory pathway and trigeminal nerve pathway, and extracellular transport along these nerves is the most possible mechanism.

Carbamazepine uptake into rat brain following intra-olfactory transport

Targeting the brain via nasal administration of drugs has been studied frequently over the last few years. In this study, a suitable gel formulation was designed to provide the absorption of a highly lipophilic drug through nasal mucosa. For this purpose, carbamazepine was chosen as the model drug. Hypromellose and Carbopol were used as mucoadhesive polymers in the formulation to increase the residence time of the gel on the mucosa. The objective of this study was to confirm the existence of a transport pathway for a drug (carbamazepine) to the brain directly from the nasal cavity, by comparing the concentration of drug in the brain after intranasal (i.n.), intravenous (i.v.), and oral (p.o.) administration. A statistically significant high level of the drug was found in the brain following intranasal administration compared with the intravenous and oral routes. These findings suggested the existence of a direct transport pathway for carbamazepine from the nasal cavity to the brain. This pathway may represent a new delivery route to the brain and central nervous system of such drugs which are needed in high and rapid concentration in the brain, especially in emergencies.

Intranasal insulin: from nose to brain

BACKGROUND

Intranasal insulin has proven useful to control hyperglycemia in diabetics but its mechanism of action has not been well defined. We attempted to understand several aspects of human insulin metabolism by measurement of and interaction of insulin and its associated moieties in nasal mucus, saliva and blood plasma under various physiological and pathological conditions.

METHODS

Insulin, insulin receptors, insulin-like growth factor 1 (IGF1) and insulin-like growth receptor 3 (IGFR3) were measured in nasal mucus, saliva and blood plasma in normal subjects, in thin and obese subjects and in diabetics under fasting and fed conditions.

RESULTS

There are complex relationships among each of these moieties in each biological fluid. Insulin and its associated moieties are present in both nasal mucus and saliva. These moieties in nasal mucus and saliva report on physiological and pathological changes in glucose metabolism as do these moieties in plasma. Indeed, insulin and its associated moieties in nasal mucus may offer specific data on how insulin enters the brain and thereby play essential roles in control of insulin metabolism.

INTERPRETATION

These data support the concept that insulin is synthesized not only in parotid glands but also in nasal serous glands. They also support the concept that insulin enters the brain following intranasal administration either 1) by direct entry through the cribriform plate, along the olfactory nerves and into brain parenchyma, 2) by entry through specific receptors in blood-brain barrier and thereby into the brain or 3) some combination of 1) and 2). Conversely, data also show that insulin introduced directly into the brain is secreted out of brain into the peripheral circulation. Data in this study demonstrate for the first time that insulin and its associated moieties are present not only in saliva but also in nasal mucus. How these complex relationships among nasal mucus, saliva and plasma occur are unclear but results demonstrate these relationships play separate yet interrelated roles in physiology and pathology of human insulin metabolism.

Drug loaded poly[Lac(Glc-Leu)] microparticles: formulation and release characteristics

Valdecoxib has been entrapped in sub-5 microm particles of poly[Lac(Glc-Leu)] copolymer using a oil-in-water (o/w) emulsification-solvent evaporation technique. To achieve monodispersed sized particles, a microfluidizer was used as ultrasonication device. Formulation parameters such as effect of polymer load, ultrasonication time, stabilizer concentration and stirring rate have a profound effect on particle size, and polydispersity. By adjustment of these parameters, microparticles ranging from about 0.8 to more than 4 microm have been prepared.

The brain targeting efficiency following nasally applied MPEG-PLA nanoparticles in rats

The aim of this study was to encapsulate nimodipine (NM) within methoxy poly(ethylene glycol)-poly(lactic acid) (MPEG-PLA) nanoparticles and to investigate its brain targeting efficiency following intranasal administration. NM-loaded nanoparticles, prepared through an emulsion/solvent evaporation technique, were characterized in terms of size, zeta potential, NM loading and in vitro release. The nanoparticles were administered intranasally to rats, and the concentrations of NM in blood, cerebrospinal fluid (CSF) and brain tissues were monitored. The contribution of the olfactory pathway to the uptake of NM in the brain was determined by calculating the brain/plasma concentration ratios and "brain drug direct transport percentage (DTP)" following intranasal administration of the nanoparticles and the solution formulation. The results showed that MPEG-PLA nanoparticles had a mean particle size of 76.5 +/- 7.4 nm, a negative surface charge and a 5.2% NM loading. In vitro release was moderate under sink conditions. The intranasal administration of nanoparticles resulted in a low but constant NM level in plasma. The ratio of AUC values of the nanoparticles to the solution was 1.56 in CSF. The olfactory bulb/plasma and CSF/plasma concentration ratios were significantly higher (P < 0.05) after application of nanoparticles than those of the nasal solution, except the ratio in olfactory bulb at 5 min. Furthermore, nasally administered nanoparticles yielded 1.6-3.3-fold greater DTP values in CSF, olfactory bulb and other brain tissues compared to nasal solution. Thus, MPEG-PLA nanoparticles demonstrated its potential on improving the efficacy of the direct nose-brain transport for drugs.

Hydroxocobalamin Uptake into the Cerebrospinal Fluid after Nasal and Intravenous Delivery in Rats and Humans

The possibility of direct transport of hydroxocobalamin from the nasal cavity into the cerebrospinal fluid (CSF) after nasal administration in rats was investigated and the results were compared with a human study. Hydroxocobalamin was given to rats (n=8) both intranasally (214 microg/rat) and intravenously (49.5 microg/rat) into the jugular vein using a Vascular Access Port (VAP). Prior to and after drug administration, blood and CSF samples were taken and analysed by radioimmunoassay. The AUCCSF/AUCplasma ratio after nasal delivery does not differ from the ratio after intravenous infusion, indicating that hydroxocobalamin enters the CSF via the blood circulation across the blood-brain barrier (BBB). This same transport route is confirmed by the cumulative AUC-time profiles in CSF and plasma, demonstrating a 30 min delay between plasma absorption and CSF uptake of hydroxocobalamin in rats and in a comparative human study. The present results in rats show that there is no additional uptake of hydroxocobalamin in the CSF after nasal delivery compared to intravenous administration, which is in accordance with the results found in humans. This indicates a predictive value of the used rat model for the human situation when studying the nose to CSF transport of drugs.

Pharmacokinetics and brain uptake of diazepam after intravenous and intranasal administration in rats and rabbits

The purpose of this study was to investigate the plasma pharmacokinetics and brain uptake of a lipophilic benzodiazepine anticonvulsant, diazepam in New Zealand white rabbits and Sprague-Dawley rats to evaluate the possible absorption pathways after intravenous and intranasal administration. The intranasal formulation was prepared by dissolving DZ and 1% sodium glycocholate into microemulsion system composed of 15% ethyl laurate, 25% Labrasol, 37.5% Transcutol P, 12.5% ethanol, and 10% water. Diazepam was administered intravenously (1 mg/kg) or intranasally (2 mg/kg) to rats and rabbits. Drug concentrations in the plasma and six different regions of the brain tissues, i.e., olfactory bulb, olfactory tract, anterior, middle, and posterior segments of cerebrum and cerebellum were analyzed by LC/MS method after solid phase extraction. After i.n. administration, DZ was rapidly absorbed into the systemic circulation, and readily and homogeneously distributed into the different regions of brain tissues with a t(max) of 5 and 10 min in rats and rabbits, respectively. The bioavailability of DZ in rat plasma (68.4%) and brain (67.7%) were 32-47% higher than those observed in rabbit plasma (51.6%) and brain (45.9%). The AUC(brain)/AUC(plasma) ratios in rabbits after i.n. administration (3.77+/-0.17) were slightly lower than from i.v. administration (4.23+/-0.08). However, in rats the AUC(brain)/AUC(plasma) ratios after i.v. (3.03+/-0.07) and i.n. (3.00+/-0.32) administration were nearly identical. The plasma pharmacokinetic and distribution studies in the two animal models clearly showed that lipophilic DZ molecules reached the brain predominantly from the blood by crossing the blood-brain barrier after i.n. administration with no significant direct nose-to-brain transport via olfactory epithelium.

Pharmacokinetics of Gastrodin in rat plasma and CSF after i.n. and i.v

The pharmacokinetic behavior of Gastrodin in rat plasma and cerebrospinal fluid (CSF) after intranasal and intravenous administration (50mg kg(-1)) was investigated. Intranasal administration of Gastrodin provided a comparable AUC in CSF compared with the intravenous administration. But Gastrodin level in plasma was very low. The ratios of AUC values of intranasal to intravenous administration were 8.85% and 105.5% in plasma and CSF, respectively. The drug targeting index (DTI) was 12.34. In conclusion, intranasal administration of Gastrodin is a promising alternative to traditional administration. Olfactory mucosa did present another pathway for transport Gastrodin to the brain.

Can nasal drug delivery bypass the blood-brain barrier?: questioning the direct transport theory

The connection between the nasal cavity and the CNS by the olfactory neurones has been investigated extensively during the last decades with regard to its feasibility to serve as a direct drug transport route to the CSF and brain. This drug transport route has gained much interest as it may circumvent the blood-brain barrier (BBB), which prevents some drugs from entering the brain. Approximately 100 published papers mainly reporting animal experiments were reviewed to evaluate whether the experimental design used and the results generated provided adequate pharmacokinetic information to assess whether the investigated drug was transported directly from the olfactory area to the CNS. In the analysis the large anatomical differences between the olfactory areas of animals and humans and the experimental conditions used were evaluated. The aim of this paper was to establish the actual evidence for the feasibility of this direct transport route in humans. Twelve papers presented a sound experimental design to study direct nose to CNS transport of drugs based on the authors' criteria. Of these, only two studies in rats were able to provide results that can be seen as an indication for direct transport from the nose to the CNS. No pharmacokinetic evidence could be found to support a claim that nasal administration of drugs in humans will result in an enhanced delivery to their target sites in the brain compared with intravenous administration of the same drug under similar dosage conditions.

Huperzine A in rat plasma and CSF following intranasal administration

This paper presents to investigate the levels of Huperzine A in plasma and CSF of rats after three different kinds of administrations and to find out whether intranasal administration is the best route to transfer the drug into the CNS. The drugs of two doses (167 and 500 microg/kg) were administered to male Sprague-Dawley rats intravenously, intranasally and intragastricly, respectively. Series plasma and cerebrospinal fluid (CSF) samples were collected from femoral artery and cisterna magna for 6h. The drug concentrations were determined by HPLC-fluorescence method. The AUC(plasma) and the AUC(CSF) of intranasal administration were 90.3% and 127.7% in low dose group (167 microg/kg) and 91.3% and 69.4% in high dose group (500 microg/kg) compared with intravenous administration. The AUC(plasma) and the AUC(CSF) of intragastric administration were 98.9% and 52.1% in high dose group (500 microg/kg) compared with intravenous administration.

Evaluation of brain-targeting for the nasal delivery of estradiol by the microdialysis method

The uptake of estradiol into the cerebrospinal fluid (CSF) after intranasal and intravenous administration in rats was investigated to study whether direct nose-CSF transport of estradiol exits or not. Animals received 0.48 mg kg(-1) estradiol randomly methylated beta-cyclodextrin (RAMEB) inclusion complex intranasally and intravenously. Following nasal delivery, estradiol reached a C(max) value (mean+/-S.D.) in plasma (26.70+/-11.37 ng ml(-1)) and CSF (54.76+/-32.84 ng ml(-1)) after 20 min in each case, while after intravenous infusion, estradiol reached a C(max) value in plasma (170.08+/-64.67 ng ml(-1)) and CSF (26.48+/-11.34 ng ml(-1)) at 5 min and 60 min, respectively. The AUC(CSF)/AUC(plasma) ratio (1.60+/-0.67) after intranasal delivery differed significantly from the ratio (0.61+/-0.16) observed after intravenous infusion (P<0.05). All these results indicate that estradiol is transported into CSF via olfactory neurons, and, hence, there is a direct transport route from the nasal cavity into the CSF for estradiol.

Uptake of fluorescein isothiocyanate-labelled dextran into the CSF after intranasal and intravenous administration to rats

With the growing number of patients suffering from central nervous system (CNS) diseases a suitable approach for drug targeting to the brain becomes more and more important. In the present study, the contribution of the nose-CSF pathway to the uptake of the model drug fluorescein isothiocyanate-labelled dextran with a molecular weight of 3.0 kDa (FD3) into the CSF was determined in rats. FD3 was administered intranasally (489 microg/rat) and by intravenous infusion (24.4 microg/ml; 119 microg/rat) in the same set of animals (n=6). Blood samples were taken from the tail vein and CSF was sampled by cisternal puncture using a stereotaxic frame. The contribution of the olfactory pathway to the uptake of FD3 into the CSF was determined by comparing the AUCCSF/AUCplasma ratios after intranasal and after intravenous application of FD3 mimicking the blood levels after intranasal delivery. No significant difference was observed between the AUCCSF/AUCplasma ratios of FD3 after intranasal administration (1.33+/-0.40%) and intravenous infusion (1.03+/-0.56%). This indicates that in rats about 1% of the amount of FD3 in plasma reaches the CSF both after nasal and intravenous administration and that no direct transport of FD3 from the nose-CSF could be found.

Pharmacokinetic behavior in plasma, cerebrospinal fluid and cerebral cortex after intranasal administration of hydrochloride meptazinol

The aim of this paper is to investigate the pharmacokinetic behavior of hydrochloride meptazinol (MEP) in plasma, cerebrospinal fluid (CSF) and cerebral cortex after intranasal administration (8 mg/kg) in male Sprague-Dawley rats. The pharmacokinetic study of intravenous administration (8 mg/kg) was also performed in rats. CSF and cerebral cortex samples were collected by serial CSF sampling and intracerebral microdialysis, respectively. The concentration of MEP in the biological samples was measured by high performance liquid chromatography (HPLC). It was determined that the absorption of MEP from the nasal cavity to systemic circulation was rapid and complete. The concentration-time profile showed a prolonged duration of MEP concentration in CSF and cortex following intranasal administration. The ratios of AUC values of intranasal to intravenous administrations were 0.96, 1.07 and 1.81 in plasma, CSF and cortex dialysate, respectively. In conclusion, intranasal administration of MEP is a promising alternative to traditional administration modes. Olfactory mucosa did not present intranasal MEP another pathway, in addition to systemic absorption, for transport to the brain.

Study on brain targeting of raltitrexed following intranasal administration in rats

PURPOSE

To investigate the levels of raltitrexed (RTX) in blood and different brain tissues in rats and to find out whether there is any direct drug transport from nasal cavity to brain tissues following intranasal (i.n.) administration.

METHODS

Raltitrexed was administered to male Sprague-Dawley rats either intranasally or intravenously. Drug concentrations in blood and brain tissues were determined at different times post dosing.

RESULTS

The plasma levels achieved after i.n. administration were significantly lower than those following intravenous (i.v.) administration (P < 0.05) before 120 min; but were significantly higher (P < 0.05) after 120 min. Following i.n. administration, RTX concentrations in different brain tissues were constantly detected for quite a long time and differed significantly from each other, the rank order being C (OB) > C (OT) > C (CR) > C (CL). On the contrary, RTX appeared only at the initial two or three time points in different brain regions after i.v. injection, and the concentrations were similar. AUC values in four brain regions by the nasal route were 54- to 121-fold compared with the i.v. route, the drug targeting index (DTI) values of nasal route were 71-158 for different brain regions, and about 99% of RTX content within 360 min in the brain were transported via the olfactory pathway.

CONCLUSIONS

These results showed that antineoplastic RTX could be directly transported into the brain via the olfactory pathway in rats.

A novel method to calculate the extent and amount of drug transported into CSF after intranasal administration

The aim of this paper is to establish a novel method to calculate the extent and amount of drug transported to brain after administration. The cerebrospinal fluid (CSF) was chosen as the target region. The intranasal administration of meptazinol hydrochloride (MEP) was chosen as the model administration and intravenous administration was selected as reference. According to formula transform, the extent was measured by the equation of X(A)CSF, infinity/X0 = Cl(CSF) AUC(0-->infinity)CSF/X0 and the drug amount was calculated by multiplying the dose with the extent. The drug clearance in CSF (Cl(CSF)) was calculated by a method, in which a certain volume of MEP solution was injected directly into rat cistern magna and then clearance was assessed as the reciprocal of the zeroth moment of a CSF level-time curve normalized for dose. In order to testify the accurateness of the method, 14C-sucrose was chosen as reference because of its impermeable characteristic across blood-brain barrier (BBB). It was found out that the MEP concentrations in plasma and CSF after intranasal administration did not show significant difference with those after intravenous administration. However, the extent and amount of MEP transported to CSF was significantly lower compared with those to plasma after these two administrations. In conclusion, the method can be applied to measure the extent and amount of drug transported to CSF, which would be useful to evaluate brain-targeting drug delivery.

Uptake of melatonin into the cerebrospinal fluid after nasal and intravenous delivery: studies in rats and comparison with a human study

PURPOSE

To investigate the possibility of direct transport of melatonin from the nasal cavity into the cerebrospinal fluid (CSF) after nasal administration in rats and to compare the animal results with a human study.

METHODS

Rats (n = 8) were given melatonin both intranasally in one nostril (40 microg/rat) and intravenously by bolus injection (40 microg/rat) into the jugular vein using a Vascular Access Port. Just before and after drug administration, blood and CSF samples were taken and analyzed by HPLC.

RESULTS

Melatonin is quickly absorbed in plasma (T(max) = 2.5 min) and shows a delayed uptake into CSF (T(max) = 15 min) after nasal administration. The melatonin concentration-time profiles in plasma and CSF are comparable to those after intravenous delivery. The AUC(CSF)/AUC(plasma) ratio after nasal delivery (32.7 +/- 6.3%) does not differ from the one after intravenous injection (46.0 +/- 10.4%), which indicates that melatonin enters the CSF via the blood circulation across the blood-brain barrier. This demonstrates that there is no additional transport via the nose-CSF pathway. These results resemble the outcome of a human study.

CONCLUSIONS

The current results in rats show that there is no additional uptake of melatonin in the CSF after nasal delivery compared to intravenous administration. This is in accordance with the results found in humans, indicating that animal experiments could be predictive for the human situation when studying nose-CSF transport.

Uptake of estradiol or progesterone into the CSF following intranasal and intravenous delivery in rats

The uptake of estradiol and progesterone into the cerebrospinal fluid (CSF) after intranasal and intravenous administration in rats was investigated. Each animal received estradiol intranasally (40 microg/rat) and by intravenous infusion (10 microg/rat) into the jugular vein using a vascular access port. Hereafter, the same set of rats was treated with progesterone intranasally (200 microg/rat) and by intravenous infusion (104 microg/rat). Following nasal delivery, both steroid hormones reach Cmax values in plasma and CSF at 15 min after administration. Intravenous infusion of estradiol and progesterone shows comparable plasma and CSF concentration-time profiles compared to the nasal route. For both hormones the AUCCSF/AUCplasma ratios (mean +/- SD) after intranasal delivery (estradiol 2.3 +/- 1.1%; progesterone 1.9 +/- 0.7%) do not differ significantly from the ratios shown after intravenous infusion (estradiol 2.0 +/- 0.6%; progesterone 2.2 +/- 0.8%). These results indicate that after nasal delivery estradiol and progesterone are rapidly absorbed into the systemic circulation, from where the non-protein bound hormones probably enter the CSF by crossing the blood-brain barrier. No extra direct nose-CSF transport could be demonstrated.

Preparation of nimodipine-loaded microemulsion for intranasal delivery and evaluation on the targeting efficiency to the brain

The purpose of this study was to improve the solubility and enhance the brain uptake of nimodipine (NM) in an o/w microemulsion, which was suitable for intranasal delivery. Three microemulsion systems stabilized by the nonionic surfactants either Cremophor RH 40 or Labrasol, and containing a variety of oils, namely isopropyl myristate, Labrafil M 1944CS and Maisine 35-1 were developed and characterized. The nasal absorption of NM from microemulsion formulation was investigated in rats. The optimal microemulsion formulation consisted of 8% Labrafil M 1944CS, 30% Cremophor RH 40/ethanol (3:1) and water, with a maximum solubility of NM up to 6.4 mg/ml, droplet size of 30.3 +/- 5.3 nm, and no ciliotoxicity. After a single intranasal administration of this preparation at a dose of 2 mg/kg, the plasma concentration peaked at 1 h and the absolute bioavailability was about 32%. The uptake of NM in the olfactory bulb from the nasal route was three folds, compared with intravenous (i.v.) injection. The ratios of AUC in brain tissues and cerebrospinal fluid to that in plasma obtained after nasal administration were significantly higher than those after i.v. administration. These results suggest that the microemulsion system is a promising approach for intranasal delivery of NM for the treatment and prevention of neurodegenerative diseases.

Serial cerebrospinal fluid sampling in a rat model to study drug uptake from the nasal cavity

Drug transport from the nasal cavity to the brain has gained much interest in the last decade. In the present study, a model was developed to determine the uptake of drugs into the cerebrospinal fluid (CSF) after nasal delivery in rats. CSF samples were taken using a cisternal puncture method. In this method, a needle is advanced through the skin and muscles overlying the atlanto-occipital membrane into the cisterna magna, while the rat is fixed in a stereotaxic frame. This method appears to be superior over cannulation of the atlanto-occipital membrane for CSF sampling. The major advantages of the puncture method is the ability of serial and simultaneous CSF and blood sampling for over 2 h in the same rat. To obtain maximal drug absorption from the nasal cavity and uptake into CSF, different positions of the rat's head (upright-90 degrees, supine-90 degrees, supine-45 degrees and supine-70 degrees angles) were tested in nasal delivery studies using hydrocortisone (HC) as a model drug. Putting the rat in the supine-90 degrees angle position increased the absorption of HC into plasma and CSF 2-fold compared to the upright-90 degrees angle position. The supine-70 degrees angle position did not change the HC plasma and CSF levels compared to the supine-90 degrees angle position. However, the supine-70 degrees angle position showed the fastest CSF sampling rate, enabling more accurate CSF sampling and therefore preferred for further studies. In conclusion, the cisternal puncture method using the supine-70 degrees and 90 degrees angle position is a suitable method to study drug transport from the nasal cavity into the CSF, with the ability of multiple CSF sampling.

Levels of dopamine in blood and brain following nasal administration to rats

The aim of this study was to investigate the levels of [(3)H]dopamine in blood, the cerebrospinal fluid (CSF) and brain tissue samples in rats and to find out whether the drug is transferred along the olfactory pathway to the central nervous system following nasal administration. [(3)H]Dopamine (50 microCi) was given to male Sprague-Dawley rats either intravenously or nasally to the right nostril. For the absorption study, blood samples were withdrawn from the carotid artery. The CSF samples were taken by cisternal puncture and then brain tissue samples were excised. The presence of unchanged dopamine in the samples was ascertained using thin layer chromatography (TLC). The radioactivity in the samples was measured using liquid scintillation. The greatest amount of the total radioactivity absorbed from the nasal mucosa into the systemic circulation was observed at the first sampling point 15 min after administration. The bioavailability of the total radioactivity was 68+/-30%. The uptake of [(3)H]dopamine in the brain was significantly higher 30 min after nasal administration than after intravenous administration (P<0.01). TLC data showed that approximately 59%, 14% and 68% of the radioactivity in the olfactory bulb, CSF and olfactory mucosa, respectively, coeluted with dopamine. In conclusion, these results show that unchanged dopamine is transferred into the olfactory bulb via the olfactory pathway in rats.

Nasal administration of a physostigmine analogue (NXX-066) for Alzheimer's disease to rats

The nasal route has been receiving attention for the administration of systemically active drugs because delivery is convenient, reliable and rapid. The aims of this study were to investigate the systemic absorption of nasally administered (3aS)-cis-1, 2, 3, 3a, 8, 8a-hexahydro-1, 3a, 8-trimethyl-pyrrolo-[2,3b]-indol-5-yl 3, 4 dihydro-2-isoquinolincarboxylate (NXX-066), a physostigmine analogue, in rats and to compare the uptake of the drug into the cerebrospinal fluid (CSF) after nasal and intravenous administration. NXX-066 (3 micromol/kg) was administered to both nostrils or into the vena jugularis of male Sprague-Dawley rats. Blood and CSF samples were obtained at regular intervals from the arteria carotis and by cisternal puncture, respectively. The concentrations of NXX-066 in the blood and CSF samples were measured using HPLC with fluorescence detection. NXX-066 was absorbed rapidly after nasal administration with the peak concentration occurring within 1.5 min. The nasal bioavailability of NXX-066 was 100+/-30% and the elimination from plasma was as rapid as that following intravenous administration. Low concentrations of NXX-066 were detected in the CSF after both intravenous and nasal administration. In conclusion, NXX-066 was rapidly and totally absorbed into the systemic circulation and uptake into the CSF was not enhanced by nasal administration in rats.

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.