Microdialysis pharmacokinetic study of scopolamine in plasma,olfactory bulb and vestibule after intranasal administration

The purpose of this study was to investigate the microdialysis pharmacokinetic of scopolamine in plasma, olfactory bulb and vestibule after intranasal administration. The pharmacokinetic study of subcutaneous and oral administration was also performed in rats. From the in vivo results, scopolamine intranasal administration can avoid hepatic first-pass effect. T_max plasma samples after intranasal administration were significantly faster than oral administration and subcutaneous injection. The relative bioavailability of intranasal administrations was 51.8–70% when compared with subcutaneous injection. Moreover, one can see that in comparison with scopolamine subcutaneous administration, scopolamine intranasal gel and solutions can increased drug target index (DTI) with olfactory bulb 1.69 and 2.05, vestibule 1.80 and 2.15, respectively. The results indicated that scopolamine can be absorbed directly through the olfactory mucosa into the olfactory bulb, and then transported to various brain tissue after intranasal administration, with the characteristics of brain drug delivery.     

Glutathione PEGylated liposomes: pharmacokinetics and delivery of cargo across the blood–brain barrier in rats

Abstract

Partly due to poor blood–brain barrier drug penetration the treatment options for many brain diseases are limited. To safely enhance drug delivery to the brain, glutathione PEGylated liposomes (G-Technology®) were developed. In this study, in rats, we compared the pharmacokinetics and organ distribution of GSH-PEG liposomes using an autoquenched fluorescent tracer after intraperitoneal administration and intravenous administration. Although the appearance of liposomes in the circulation was much slower after intraperitoneal administration, comparable maximum levels of long circulating liposomes were found between 4 and 24?h after injection. Furthermore, 24?h after injection a similar tissue distribution was found. To investigate the effect of GSH coating on brain delivery in vitro uptake studies in rat brain endothelial cells (RBE4) and an in vivo brain microdialysis study in rats were used. Significantly more fluorescent tracer was found in RBE4 cell homogenates incubated with GSH-PEG liposomes compared to non-targeted PEG liposomes (1.8-fold, p?<?0.001). In the microdialysis study 4-fold higher (p?<?0.001) brain levels of fluorescent tracer were found after intravenous injection of GSH-PEG liposomes compared with PEG control liposomes. The results support further investigation into the versatility of GSH-PEG liposomes for enhanced drug delivery to the brain within a tolerable therapeutic window.     

Lidocaine distribution into the CNS following nasal and arterial delivery: a comparison of local sampling and microdialysis techniques

The disposition of lidocaine within the CNS of the rat following nasal and intra-arterial delivery was characterized using a microdialysis technique. Lidocaine concentrations in the cisterna magna were determined using microdialysis and compared to those previously determined using a direct CSF sampling method. The disposition profiles for lidocaine into the cisternal CSF obtained using microdialysis were found to be similar to those obtained by direct CSF sampling techniques over an initial 120-min interval. In other experiments, lidocaine disposition in the right (dosed side) and left olfactory bulb following nasal (i.n.) and intra-arterial (i.a.) administration was studied using microdialysis. The lidocaine concentrations in the ipsilateral olfactory bulb were slightly higher after drug administration into the nasal cavity than those in the contralateral olfactory bulb over the initial 20-min sampling interval. Drug concentrations found in the right olfactory bulb were not significantly different from those found in the left olfactory bulb following intra-arterial administration. Comparisons of lidocaine disposition in the right olfactory bulb and cerebellum, two CNS sites with the same regional vascular supply, showed that the disposition patterns were nearly identical for the two sites following i.a. administration. There was a significant lengthening in the t_max at both sites following i.n. delivery compared to i.a. delivery, and the relative concentrations at each site were no longer equivalent. From these results, it appears that the microdialysis technique is a useful tool for studying drug distribution into the CNS. The changes in disposition patterns between i.a. and i.n. administration indicate that other factors or pathways, in addition to the systemic circulation, play a role in the transport of lidocaine into the brain following nasal administration.     

Evaluation of brain targeting in rats of Salvianolic acid B nasal delivery by the microdialysis technique

The purpose of this study was to investigate the biodistribution of Salvianolic acid B in rats blood and brain after intranasal administration and explore its feasibility and evaluate its brain targeting effect. The concentration of Salvianolic acid B in blood and brain following nasal administration (32?mg?kg^?1) was measured combining with microdialysis sampling and liquid chromatograph-mass spectrometer/MS detection technology. After the microdialysis samples were corrected with in vivo recoveries, the pharmacokinetic parameters were obtained by using non-compartment model and the brain targeting evaluated by the value of drug targeting index (DTI). The C_max in blood and brain by intravenous injection were higher than intranasal administration, but the intranasal administration of MRT_0-∞ significantly prolonged and increased by nearly 2.03 and 1.86 times, respectively. The DTI value of Salvianolic acid B was 5.54 and bioavailability (F) was 43.98%. After nasal administration of Salvianolic acid B, it has a certain brain targeting, which could become a new drug system for the treatment of brain diseases.     

Functional Evidence for P-glycoprotein at the Nose-Brain Barrier

No HeadingPurpose. Experiments were performed to assess the brain distribution of [³H]-verapamil, including the influence of delivery route of inhibitor and substrate (nasal vs. systemic) on brain distribution. The anatomic location of P-glycoprotein (P-gp) at the nose-brain barrier also was investigated.Methods. Separate groups of mice were pretreated with rifampin or vehicle nasally or intravenously. [³H]-verapamil was administered either nasally or via in situ brain perfusion, and dose-response profiles were constructed for P-gp inhibition. Localization of P-gp in freshly obtained brain slices and olfactory tissue was evaluated by confocal microscopy.Results. Rifampin inhibited the P-gp–mediated efflux of [³H]-verapamil, regardless of delivery route (I_max = 62 ± 6%). The ED₅₀ for enhancement of [³H]-verapamil uptake by nasal rifampin was 400-fold lower than for intravenous rifampin (0.16 vs. 65 mg/kg, respectively). Microscopy showed that P-gp was located in endothelial cells that line the olfactory bulb and within the olfactory epithelium.Conclusion. Nasal delivery of rifampin enhanced brain uptake of [³H]-verapamil. The magnitude of transport inhibition was dependent on the dose and route of the inhibitor, the time after administration of the inhibitor, and the specific brain region examined. P-gp is localized to both the olfactory epithelium and the endothelial cells that surround the olfactory bulb.     

Transfer of Dopamine in the Olfactory Pathway Following Nasal Administration in Mice

Purpose. The aim of the study was to investigate whetherdopamine is transferred along the olfactory pathway to the brain followingnasal administration to mice. Methods. [³H]-Dopamine was administered nasally or intravenouslyto female mice. Brain tissue samples were excised and the radioactivecontent was measured. The precise localisation of dopamineradioactivity in the brain was studied using autoradiography. The presence ofdopamine or its metabolites in the olfactory bulb and mucosa wasascertained using thin layer chromatography (TLC). Results. After administration of [³H]-dopamine into the rightnostril, the amount of dopamine in the right bulb increased with time until,after 4 h, it was 27 times higher than in the left bulb. Among the otherbrain tissue samples, significantly higher amount of radioactivity wasdetected in the lateral olfactory tract. Radioactivity in the right olfactorybulb was shown by autoradiography to be selectively located in theperipheral layers 1 to 4 h after administration. Selective uptake ofradioactivity was not seen in other regions of the brain. TLC dataindicated that approximately 75% and 10% of the radioactivity in theolfactory bulb and mucosa, respectively, coeluted with dopamine. Conclusions. The results indicate that unchanged dopamine istransferred into the olfactory bulb following nasal administration of[³H]-dopamine.     

Brain distribution of ribavirin after intranasal administration

Ribavirin has proved to be effective in vitro against several RNA viruses responsible for encephalitis in humans and animals. However, the in vivo efficacy towards the cerebral viral load seems to be limited by the blood–brain barrier. Since the nose-to-brain pathway has been indicated for delivering drugs to the brain, we investigated here the distribution of ribavirin in the central nervous system (CNS) after intranasal administration. We first tested in vitro ribavirin diffusion from an aqueous solution across a biological membrane, using Franz cells and rabbit nasal mucosa. About 35% of ribavirin permeated in 4 h across the mucosa, after reaching steady-state flux in less than 30 min. In the first in vivo experiment, ribavirin aqueous solution was administered intranasally to Sprague Dawley rats (10 mg/kg). Animals were sacrificed at 10, 20 or 30 min after administration to collect brain areas (cerebellum, olfactory bulb, cerebral cortex, basal ganglia and hippocampus) and biological fluids (cerebrospinal fluid and plasma). Ribavirin, quantified by LC–MS/MS spectrometry, was detected at each time point in all compartments with the highest concentration in olfactory bulb and decreasing in rostro-caudal direction. Two subsequent in vivo experiments compared the nasal route (ribavirin solution) with the intravenous one and the nasal administration of ribavirin solution with ribavirin powder (10 mg/kg). It was found that 20 min after administration, ribavirin concentration in olfactory bulb was similar after intravenous or nasal administration of the ribavirin solution, whereas the powder led to significantly higher levels. Ribavirin was also present in deeper compartments, such as basal ganglia and hippocampus.Even if the mechanisms involved in ribavirin nose-to-brain transport are not clear, these results suggest a rapid extracellular diffusive flux from the nasal epithelium to the olfactory bulb and different CNS areas.     

Sodium hyaluronate as a mucoadhesive component in nasal formulation enhances delivery of molecules to brain tissue

Intranasal administration of molecules has been investigated as a non-invasive way for delivery of drugs to the brain in the last decade. Circumvention of both the blood-brain barrier and the first-pass elimination by the liver and gastrointestinal tract is considered as the main advantages of this method. Because of the rapid mucociliary clearance in the nasal cavity, bioadhesive formulations are needed for effective targeting. Our goal was to develop a formulation containing sodium hyaluronate, a well-known mucoadhesive molecule, in combination with a non-ionic surfactant to enhance the delivery of hydrophilic compounds to the brain via the olfactory route. Fluorescein isothiocyanate-labeled 4 kDa dextran (FD-4), used as a test molecule, was administered nasally in different formulations to Wistar rats, and detected in brain areas by fluorescent spectrophotometry. Hyaluronan increased the viscosity of the vehicles and slowed down the in vitro release of FD-4. Significantly higher FD-4 transport could be measured in the majority of brain areas examined, including olfactory bulb, frontal and parietal cortex, hippocampus, cerebellum, midbrain and pons, when the vehicle contained hyaluronan in combination with absorption enhancer. The highest concentrations of FD-4 could be detected in the olfactory bulbs, frontal and parietal cortex 4 h after nasal administration in the mucoadhesive formulation. Intravenous administration of a hundred times higher dose of FD-4 resulted in a lower brain penetration as compared to nasal formulations. Morphological examination of the olfactory system revealed no toxicity of the vehicles. Hyaluronan, a non-toxic biomolecule used as a mucoadhesive in a nasal formulation, increased the brain penetration of a hydrophilic compound, the size of a peptide, via the nasal route.     

Nasal Toxicity of Manganese Sulfate and Manganese Phosphate in Young Male Rats Following Subchronic (13-Week) Inhalation Exposure

Growing evidence suggests that nasal deposition and transport along the olfactory nerve represents a route by which inhaled manganese and certain other metals are delivered to the rodent brain. The toxicological significance of olfactory transport of manganese remains poorly defined. In rats, repeated intranasal instillation of manganese chloride results in injury to the olfactory epithelium and neurotoxicity as evidenced by increased glial fibrillary acidic protein (GFAP) concentrations in olfactory bulb astrocytes. The purpose of the present study was to further characterize the nasal toxicity of manganese sulfate (MnSO₄) and manganese phosphate (as hureaulite) in young adult male rats following subchronic (90-day) exposure to air, MnSO₄ (0.01, 0.1, and 0.5 mg Mn/m³), or hureaulite (0.1 mg Mn/m³). Nasal pathology, brain GFAP levels, and brain manganese concentrations were assessed immediately following the end of the 90-day exposure and 45 days thereafter. Elevated end-of-exposure olfactory bulb, striatum, and cerebellum manganese concentrations were observed following MnSO₄ exposure to ≥0.01, ≥0.1, and 0.5 mg Mn/m³, respectively. Exposure to MnSO₄ or hureaulite did not affect olfactory bulb, cerebellar, or striatal GFAP concentrations. Exposure to MnSO₄ (0.5 mg Mn/m³) was also associated with reversible inflammation within the nasal respiratory epithelium, while the olfactory epithelium was unaffected by manganese inhalation. These results confirm that high-dose manganese inhalation can result in nasal toxicity (irritation) and increased delivery of manganese to the brain; however, we could not confirm that manganese inhalation would result in altered brain GFAP concentrations.     

Manipulation of olfactory tight junctions using papaverine to enhance intranasal delivery of gemcitabine to the brain

Abstract

Context: Delivery of drugs from the nasal cavity to the brain is becoming more widely accepted, due to the non-invasive nature of this route and the ability to circumvent the blood brain barrier (BBB).

Objective: Because of similarities in the proteins comprising the olfactory epithelial tight junction (TJ) proteins and those of the BBB, we sought to determine whether papaverine (PV), which is known to reversibly enhance BBB permeability, could increase the delivery of intranasally administered gemcitabine to the central nervous system in rats.

Experimental methods: Included intranasal administration of gemcitabine, fluorescein isothiocyanate-dextran beads and PV, histopathology, immunostaining, RT-PCR, western blot analysis, immunofluorescence localization, spectrofluorometric analysis, in vivo brain microdialysis, HPLC analysis and in vitro gemcitabine recovery.

Results and discussion: PV transiently decreased the levels and altered immunolocalization of the TJ protein phosphorylated-occludin in the olfactory epithelium, while causing an approximately four-fold increase in gemcitabine concentration reaching the brain. The enhanced delivery was not accompanied by nasal epithelial damage or toxicity to distant organs.

Conclusions: The ability to transiently and safely increase drug delivery from the nose to the brain represents a non-invasive way to improve treatment of patients with brain disorders.     

Nasal in-situ gels for delivery of rasagiline mesylate: improvement in bioavailability and brain localization

Abstract

Intranasal thermosensitive gel for rasagiline mesylate (RM) was developed for effective treatment of Parkinson’s disease. Intranasal gels were prepared by combination of poloxamer 407 and poloxamer 188 (1:1) with mucoadhesive polymers (carbopol 934?P and chitosan). The formulations were evaluated for sol–gel transition temperature, in-vitro drug release and in-vivo mucociliary transit time. Further, optimal intranasal gel formulations were tested for in-vivo pharmacokinetic behavior, nasal toxicity studies and brain uptake studies. It was found that optimal formulations had acceptable gelation temperature (28–33?°C) and adequate in-vitro drug release profile. Pharmacokinetic study in rabbits showed significant (p?<?0.05) improvement in bioavailability (four- to six-folds) of the drug from intranasal gels than oral solution. Chronic exposure studies in Wistar rats showed that these intranasal gels were non-irritant and non-toxic to rat nasal mucosa. Estimation of RM in rat brain tissue showed significant (p?<?0.01) improvement in uptake of RM form intranasal gel formulations than nasal solution.     

Transfer of Some Carboxylic Acids in the Olfactory System Following Intranasal Administration

Abstract

The uptake of [¹⁴C]benzoic acid, 4-chloro[¹⁴C]benzoic acid, [³H]phthalic acid and [¹⁴C]salicylic acid in the nasal passages and brain was determined following a unilateral intranasal instillation in mice. An uptake of radioactivity from the nasal mucosa to the ipsilateral olfactory bulb was observed up to 4 h after administration following intranasal instillation of these carboxylic acids whereas the level was low in the contralateral olfactory bulb. Autoradiography of mice given [¹⁴C]benzoic acid and [¹⁴C]salicylic acid by intranasal instillation showed a preferential localization of radioactivity in the axonal and glomerular layer of the olfactory bulb 1 h after the administration. Four hours after administration the radioactivity was present as a gradient from the axonal layer towards the center of the olfactory bulb. Pretreatment of mice with a compound known to damage the olfactory neuroepithelium resulted in a decreased uptake of [¹⁴C]benzoic acid in the olfactory bulb. Thin layer chromatography of supernatants from the ipsilateral olfactory bulbs of mice given [¹⁴C]benzoic acid by nasal instillation indicated that the radioactivity in the bulbs represented unchanged compound. These results suggest that there is a transfer of some aromatic carboxylic acids in the olfactory pathways.     

Brain uptake of dihydroergotamine after intravenous and nasal administration in the rat

This study was conducted to determine the uptake of dihydroergotamine (DHE) into the brain after intravenous and intranasal administration in rats. Eight anesthetized rats received either an intravenous (i.v.) or two successive intranasal (i.n.) doses of tritium labeled dihydroergotamine (³H-DHE) with ¹⁴C-inulin as a non-BBB (blood–brain barrier) permeable marker. Radioactivity concentrations in plasma were determined at designated times within 30 min postdose, and in blood and seven brain regions (olfactory bulb, frontal cortex, parietal cortex, occipital cortex, cerebellum, mid-brain areas, and brain stem) at 30 min. The plasma-to-brain permeability*area product (PeA) following an i.v. dose was calculated based on the 30-min brain tissue concentration and the area under the plasma concentration–time curve (AUC_{0–30 min, i.v.}) assuming unidirectional transport from plasma to brain. Direct transport from nasal cavity to brain was assessed based on the amount of radioactivity in brain determined experimentally and predicted based on plasma AUC_{0–30 min, i.n.} and PeA obtained from i.v. data. Following an i.v. dose, DHE distributed into the brain with a brain-to-plasma concentration ratio of ∼5% at 30 min postdose. The PeA value of DHE ranged from 8.6×10⁻⁴ to 37.5×10⁻⁴ mL min⁻¹ g⁻¹ in different brain regions. Following i.n. doses the experimentally determined concentration in olfactory bulb was approximately 51 times, and in other regions three to seven times, greater than predicted values based only on PeA and plasma AUC, suggesting a direct transport pathway from the nasal cavity to the brain. As a result, the brain tissue concentrations at 30 min were similar to (0.31–1.04 times) those following an i.v. dose except for the olfactory bulb, in which the concentration was approximately four times greater than that following an i.v. dose. In conclusion, ³H-DHE penetrated the BBB following intravenous administration. Following i.n. doses, ³H-DHE was able to enter the brain directly from the nasal cavity, with the olfactory bulb being a part of the direct passage from nasal cavity to brain. Copyright © 1998 John Wiley & Sons, Ltd.     

Enhancement of the Systemic and CNS Specific Delivery of L-Dopa by the Nasal Administration of Its Water Soluble Prodrugs

Purpose. To study the utility of the nasal route for thesystemic delivery of L-dopa using water soluble prodrugs of L-dopa and toexamine if this delivery method will result in preferential delivery to theCNS. Methods. Several alkyl ester prodrugs of L-dopa wereprepared and their physicochemical properties were determined. Invitro hydrolysis rate constants in buffer, rat plasma, rat brainhomogenate, rat CSF, and rat nasal berfusate were determined by HPLC. Invivo nasal experiments were carried out in rats. Levels of L-dopa anddopamine in plasma, CSF, and olfactory bulb were determined using HPLCmethod with electrochemical detection. Results. All the prodrugs showed improved solubility andlipophilicity with relatively fast in vitro conversion in ratplasma. Absorption was fast following nasal delivery of the prodrugs withbioavailability around 90%. Dopamine plasma levels did not changesignificantly following nasal administration of the butyl ester prodrug.Olfactory bulb and CSF L-dopa concentration were higher following nasaldelivery of the butyl ester prodrug compared to an equivalent intravenousdose. Conclusions. Utilization of water soluble prodrugs ofL-dopa via the nasal route in the treatment of Parkinson's disease may havetherapeutic advantages such as improved bioavailability, decreased sideeffects, and potentially enhanced CNS delivery.     

Enhancement of nose-brain delivery of therapeutic agents for treating neurodegenerative diseases using peppermint oil

The nose-brain pathway is a potential route for drug delivery as it bypasses the brain barriers. The main objective of this study was to investigate the efficacy of peppermint oil in enhancing the bioavailability of intranasally administered neurotrophins like nerve growth factor (NGF). The effect of different concentrations of peppermint oil (PO) on the delivery of NGF across bovine olfactory epithelium was studied in vitro using Franz diffusion cells. Trans-olfactory epithelial electrical resistance (TEER) was measured to assess the permeability status of the bovine olfactory epithelium. The bioavailability of intranasally administered formulations in rat hippocampus was studied by carrying out brain microdialysis in male Sprague-Dawley rats. Peppermint oil at concentrations of 0.05, 0.1 and 0.5% v/v enhanced the in vitro transport of NGF by 5, 7 and 8 fold, respectively. In vivo studies employing brain microdialysis in rats demonstrated that intranasal administration of NGF formulation with 0.5% PO enhanced the bioavailability by approximately 8 fold compared to rats administered with NGF alone. The bioavailability of NGF in the brain could be enhanced by intranasal administration of peppermint oil.     

Enhancement of Nasal Delivery of a Renin Inhibitor in the Rat Using Emulsion Formulations

Nasal absorption of O-(N-morpholino-carbonyl-3-L-phenylaspartyl-L-leucinamide of (2S,3R,4S)-2-amino-1-cyclohexyl-3,4-dihydroxy-6-methylheptane (I), a renin inhibitor, was evaluated in two rat nasal models, one involving surgery and the other requiring no surgical intervention. Oleic acid/monoolein emulsion formulations were tested along with a control PEG 400 solution. The percent absolute bioavailability of the compound was enhanced from 3–6% (PEG 400 solution) to 15–27% when the emulsion formulations were used. The different nasal model techniques (with and without surgery) did not produce any statistical difference in the absolute bioavailability values for I. Emulsion formulations did not produce appreciable damage as assessed morphologically. It is suggested that emulsion formulations containing membrane adjuvants such as oleic acid and monoolein can be used to enhance the nasal delivery of low-bioavailable, lipid-soluble drugs.____________________     

A microdialysis model to examine nasal drug delivery and olfactory absorption in rats using lidocaine hydrochloride as a model drug

Targeting of the central nervous system by direct drug transport from the nose to the brain has gained increased attention through the last decade. In the present study, a model for olfactory drug absorption has been investigated using intravenous and unilateral nasal administration of lidocaine hydrochloride in rats. To investigate the possible drug delivery aspects of this route of transport to a central part of the brain a microdialysis model using in vivo recovery by calibrator was applied to the systemic blood and to right and left striatum. The integrity of the blood-brain barrier was evaluated following microdialysis probe implantation. The in vivo experiments were carried out as a cross-over study in rats. The drainage from the nasal cavity was not restricted by occlusion. It was found that true unbound lidocaine concentrations could be calculated from in vivo recovery measurements of retrodialysis of prilocaine hydrochloride. The relative in vivo recoveries in striatum (11.3%) and blood (24.0%) were significantly lower than in vitro (31.3 and 44.9%). The blood-brain barrier was found to retain its physical integrity when evaluated one hour after probe implantation. From pharmacokinetic modelling of the time-concentration curves it was found that the absorption rates and area under the curve (AUC) values of lidocaine in left and right striatum were not statistically different following nasal and intravenous administration, respectively. The average nasal bioavailabilities of lidocaine in blood, left and right striatum were 85, 103 and 129%, respectively. It was concluded that no significant olfactory absorption to striatum was evident in the present study. However, the method should be applicable to studies of drug delivery to blood and brain following nasal administration of other drugs.     

Drug brain distribution following intranasal administration of Huperzine A in situ gel in rats

AIM: To determine the uptake extent of Huperzine A (Hup A) into the brain after intranasal administration of Hup A in situ gel to rats, and to compare the pharmacokinetic parameters between intranasal administration and iv and po. METHODS: Hup A was administered to male Sprague-Dawley rats via nasal, iv and oral routes at the dose of 166.7, 166.7, and 500 mug/kg, respectively. Blood and brain tissue samples including the cerebrum, hippocampus, cerebellum and olfactory bulb were collected, and the concentrations of Hup A in the samples were assayed by HPLC. The area under the concentration-time curve (AUC(0-->6 h)) and the ratio of the AUC(brain) to the AUC(plasma) (drug targeting efficiency, DTE) were calculated to evaluate the brain targeting efficiency of the drug via 3 administration routes. RESULTS: The AUC(0-->6 h) of the drug in the cerebrum, hippocampus, cerebellum, left olfactory bulb and right olfactory bulb after intranasal administration of the Hup A in situ gel were 1.5, 1.3, 1.0, 1.2, and 1.0 times of those after iv administration of the injection, and 2.7, 2.2, 1.9, 3.1, and 2.6 times of those after administration of the oral formulation. The AUC (brain0-->6 h)/AUC(plasma0-->6 h) of Hup A in the cerebrum, hippocampus and left olfactory bulb following the intranasal administration dose were significantly higher (P<0.05) than the iv dose. CONCLUSION: Intranasal delivery showed a viable, non-invasive strategy for delivering the drug into brain.     

Brain distribution of ribavirin after intranasal administration

Ribavirin has proved to be effective in vitro against several RNA viruses responsible for encephalitis in humans and animals. However, the in vivo efficacy towards the cerebral viral load seems to be limited by the blood–brain barrier. Since the nose-to-brain pathway has been indicated for delivering drugs to the brain, we investigated here the distribution of ribavirin in the central nervous system (CNS) after intranasal administration. We first tested in vitro ribavirin diffusion from an aqueous solution across a biological membrane, using Franz cells and rabbit nasal mucosa. About 35% of ribavirin permeated in 4 h across the mucosa, after reaching steady-state flux in less than 30 min. In the first in vivo experiment, ribavirin aqueous solution was administered intranasally to Sprague Dawley rats (10 mg/kg). Animals were sacrificed at 10, 20 or 30 min after administration to collect brain areas (cerebellum, olfactory bulb, cerebral cortex, basal ganglia and hippocampus) and biological fluids (cerebrospinal fluid and plasma). Ribavirin, quantified by LC–MS/MS spectrometry, was detected at each time point in all compartments with the highest concentration in olfactory bulb and decreasing in rostro-caudal direction. Two subsequent in vivo experiments compared the nasal route (ribavirin solution) with the intravenous one and the nasal administration of ribavirin solution with ribavirin powder (10 mg/kg). It was found that 20 min after administration, ribavirin concentration in olfactory bulb was similar after intravenous or nasal administration of the ribavirin solution, whereas the powder led to significantly higher levels. Ribavirin was also present in deeper compartments, such as basal ganglia and hippocampus.Even if the mechanisms involved in ribavirin nose-to-brain transport are not clear, these results suggest a rapid extracellular diffusive flux from the nasal epithelium to the olfactory bulb and different CNS areas.     

石杉碱甲鼻用原位凝胶的制备及其经鼻脑靶向性评价

目的探索利用鼻腔嗅觉区的鼻-脑通道开发经鼻脑靶向给药系统的可行性。方法用阳离子敏感性成胶辅料结冷胶，采用pH梯度沉淀法制备了石杉碱甲鼻用原位凝胶。以市售片剂和注射液为对照，用小脑延髓池插管法采集脑脊液，股动脉插管取血，测定其在大鼠脑脊液和血中药物动力学参数；用组织匀浆法，测定其在大鼠脑组织中的分布；用Morris水迷宫法、跳台法和避暗法试验其对大鼠和小鼠模型的药效。结果大鼠鼻腔给药血浆AUC_{0→6 h}为静注的0.94倍，但脑脊液AUC_{0→6 h}为静注和灌胃的1.3和2.3倍；大鼠鼻腔给药后大脑、海马、小脑、左右嗅球的AUC_{0→6 h}分别为静注的1.5，1.3，1.0，1.2和1.0倍，为灌胃的2.7，2.2，1.9，3.1和2.6倍。药效学研究表明以1/4～1/2口服剂量鼻腔给药与口服等效，与药动学结果相符。结论石杉碱甲原位凝胶鼻腔给药较静注和灌胃显著增加了药物在脑内，特别在其改善记忆障碍作用的靶部位——大脑和海马的分布，提高了药物的脑靶向性。