Thermally reversible xyloglucan gels as vehicles for nasal drug delivery

The aim of this study was to investigate the potential application of thermosensitive gels formed by a xyloglucan polysaccharide derived from tamarind seed for nasal drug delivery. Xyloglucan that had been partially degraded by β-galactosidase to eliminate 45% of galactose residues formed gels at concentrations of 2.5% w/w at gelation temperatures decreasing over the range 27–28°C. The in vitro release of ondansetron hydrochloride from the enzyme-degraded xyloglucan gels followed higuchi kinetics over a period of 5?h at 34°C by anomalous transport mechanism. The ex vivo permeation of ondansetron hydrochloride from the gels was sustained. Histological examination of nasal mucosa following a single administration of the gels showed no evidence of mucosal damage. Finally, the bioavailability study in rabbits revealed that the absolute bioavailability of ondansetron hydrochloride was significantly increased from 28.64% in the case of the oral drug solution to 52.79% in the case of the nasal in situ gel. The results of this study suggest the potential of the enzyme-degraded xyloglucan gels as vehicles for nasal delivery of drugs.     

薄荷脑鼻腔原位凝胶剂的制备及安全性研究

目的 制备薄荷脑鼻用原位凝胶剂,并对其进行安全性考察。方法 采用去乙酰结冷胶为材料制备离子敏感性原位凝胶。考察鼻腔原位凝胶对蟾蜍鼻黏膜纤毛的毒性及大鼠鼻黏膜的影响;并进行家兔皮肤刺激实验和豚鼠皮肤过敏实验,观察皮肤反应并评分。结果 薄荷脑鼻用原位凝胶剂对蟾蜍鼻黏膜纤毛无显著毒性,对大鼠鼻黏膜形态及细胞分化无显著影响;对家兔完整皮肤无刺激作用,豚鼠皮肤无过敏反应。结论 薄荷脑鼻用原位凝胶剂具有制备工艺简便、纤毛毒性低、生理相容性好的优点,开发为经鼻给药系统可行性良好。     

Smart Polymers in Nasal Drug Delivery

Nasal drug delivery has now been recognized as a promising route for drug delivery due to its capability of transporting a drug to systemic circulation and central nervous system. Though nasal mucosa offers improved bioavailability and quick onset of action of the drug, main disadvantage associated with nasal drug delivery is mucocilliary clearance due to which drug particles get cleared from the nose before complete absorption through nasal mucosa. Therefore, mucoadhesive polymeric approach can be successfully used to enhance the retention of the drug on nasal mucosal surface. Here, some of the aspects of the stimuli responsive polymers have been discussed which possess liquid state at the room temperature and in response to nasal temperature, pH and ions present in mucous, can undergo in situ gelation in nasal cavity. In this review, several temperature responsive, pH responsive and ion responsive polymers used in nasal delivery, their gelling mechanisms have been discussed. Smart polymers not only able to enhance the retention of the drug in nasal cavity but also provide controlled release, ease of administration, enhanced permeation of the drug and protection of the drug from mucosal enzymes. Thus smart polymeric approach can be effectively used for nasal delivery of peptide drugs, central nervous system dugs and hormones.     

Characterization and localization of thromboxane A2 receptor in human and guinea-pig nasal mucosa using radiolabelled (+)-S-145

1. TxA₂ receptor (TP-receptor) antagonists such as S-1452 and Bay u 3405 have been shown to be effective in alleviating nasal blockage in patients with allergic rhinitis as well as guinea-pig allergic rhinitis models. The present study was conducted to examine the existence and localization of the TP-receptor in human and guinea-pig nasal mucosa by in vitro receptor binding autoradiography using radiolabelled (+)-S-145, which is a potent and specific TP-receptor antagonist with an extremely slow dissociation rate.
2. We ascertained the binding specificity of [³H]-(+)-S-145 in human and guinea-pig platelet membranes by comparing the ability of four TP-receptor ligands of U-46619, (+)-S-145, I-(+)-S-145 and Bay u 3405 to displace the specific binding of [³H]-(+)-S-145 and [³H]-U-46619. The rank order of potency (K_i) for the displacement was correlated highly with that determined from [³H]-U-46619 binding to the same preparations.
3. Quantitative autoradiography using a radioluminographic imaging plate system, in which the radioactivity of [³H]-(+)-S-145 is expressed as photostimulated luminescence (PSL) per area (mm²), revealed that specific binding of [³H]-(+)-S-145 to human and guinea-pig nasal mucosa was saturable. Scatchard analysis showed about three fold higher affinity and two fold greater maximal binding to the nasal mucosa of humans than that of guinea-pigs: the K_D and B_max values in human mucosa were 2.82±0.35 nM and 6.47±0.33 PSL mm⁻² and those in guinea-pig mucosa were 8.23±1.93 nM and 3.37±0.66 PSL mm⁻², respectively.
4. Specific [³H]-(+)-S-145 binding to cryostat sections of human and guinea-pig nasal mucosa was displaced by another TP-receptor antagonist, Bay u 3405, and a TP-receptor agonist, U-46619. The order of potency (K_i value: nM) was (+)-S-145 (2.5) > Bay u 3405 (15.4) >> U-46619 (359.6) in human nasal mucosa and (+)-S-145 (22.8) > U-46619 (49.8) ≈amp; Bay u 3405 (62.1) in guinea-pig nasal mucosa. These rank orders showed rather good correlation with those obtained for the respective platelet membranes.
5. Autoradiographs of human nasal mucosa demonstrated that specific [¹²⁵I]-(+)-S-145 binding sites mainly exist on the smooth muscle layers of venous sinusoids and arterioles in the lamina propria, with few or no binding sites in the epithelium and nasal gland.
6. We concluded that radiolabelled (+)-S-145 can be used as a TP-receptor ligand for autoradiographic study, and that the TP-receptor is exclusively located on smooth muscle layers of venous sinusoids and arterioles in the nasal mucosa. The potent vasoconstrictive activity of TxA₂ may cause reduction of local blood flow followed by mucosal oedema probably through mechanisms of vascular injury such as ischaemia-reperfusion.

     

鼻腔给药系统的研究新进展

近年来药物的鼻腔给药系统受到了越来越多的关注.全球众多制药行业都在致力于基因和多肽类药物新型鼻腔给药系统的研发.现阐述了鼻腔生理特点和药物鼻黏膜转运机制及其影响因素,并对近年来鼻腔给药系统的促吸收途径和发展动向作一概述.     

重组水蛭素-2在家兔鼻黏膜中降解的体外实验

目的考察重组水蛭素-2(rHV2)在家兔鼻黏膜中的降解情况。方法建立用HPLC测定家兔鼻黏膜和肠黏膜组织匀浆液中rHV2浓度的方法；测定不同浓度rHV2在家兔鼻黏膜组织匀浆液中及rHV2在不同pH值的家兔鼻黏膜组织匀浆液中的降解；比较家兔鼻黏膜和肠黏膜组织匀浆液对rHV2的降解；考察rHV2在家兔鼻黏膜酶提取液中的稳定性以及加入酶抑制剂对rHV2在家兔鼻黏膜组织匀浆液降解的抑制作用。结果rHV2在鼻黏膜匀浆液中的降解具有明显的药物浓度和pH依赖性；rHV2在鼻黏膜匀浆液中的稳定性优于在肠黏膜匀浆液中的稳定性；鼻黏膜酶提取液对rHV2的降解作用较小；酶抑制剂杆菌肽对rHV2在鼻黏膜匀浆液中的降解具有一定的抑制作用。结论与口服给药途径相比，rHV2鼻腔给药更有优势。     

Effects of formulation variables on nasal epithelial cell integrity: Biochemical evaluations

The effects of pH, osmolarity, type and concentration of buffers on the nasal mucosal epithelium have been investigated in rats using an in situ nasal perfusion technique. Traditionally, histological approaches which are qualitative and not predicative of nasal mucosal sensitivity, have been used to assess the damage to the nasal mucosa. A biochemical approach has been used in this report to assess irritation to the nasal mucosa which may provide a priori indication of nasal sensitivity to chronic use of nasal formulations. The nasal mucosal irritation may be predicted by determining the amount of total protein and two enzymes, lactate dehydrogenase (LDH, EC 1.1.1.27), a cytosolic enzyme and 5′-nucleotidase (5′-ND, EC 3.1.3.5), a membrane-bound enzyme released during perfusion. To determine the effect of pH on the nasal mucosa, phosphate buffers ranging in pH from 2 to 12 were utilized. Solutions within a pH range of 3–10 caused minimal release of the biochemical markers whereas solutions of pH above 10 caused significant membrane and intracellular enzyme release. Acetate buffers (pH 4.75) at three different concentrations, 0.07, 0.14 and 0.21 M, were used to study the effect of buffer concentration on the nasal mucosal integrity. The results indicate that the alteration to the nasal mucosal cells by buffers is concentration dependent. To study the effect of buffer type, four different buffers, i.e., acetate, adipate, citrate, and phosphate (0.07 M, pH 4.75) were studied. The acetate buffer was found to have the most irritation potential when compared to adipate, citrate, and phosphate buffers. To determine the effects of unionized and ionized species of a buffer, 0.025 M benzoate buffers at pH 3.2 and 5.2 were studied. The results indicate that the unionized species of benzoic acid causes more cellular perturbation than the ionized species. Hypertonic and isotonic sodium chloride solutions caused minimal mucosal cell aberrations while hypotonic solutions caused extensive leakage of LDH. These results along with other results from our laboratory may help in designing well tolerated nasal formulations for chronic use.     

Nasal retention of budesonide and fluticasone in man: formation of airway mucosal budesonide-esters in vivo

AIMS: The efficacy of topical glucocorticosteroids in rhinitis and asthma is likely to depend on drug retention in the airway mucosa. With fluticasone propionate, retention may be achieved exclusively by lipophilicity, whereas for budesonide an additional possibility may be provided by its ability to form fatty acid esters in the airway mucosa that release the active drug. The aim of the present study was to determine the nasal mucosal retention of budesonide and fluticasone propionate, and the occurrence of budesonide-esters (budesonide-oleate, budesonide-palmitate) in the nasal mucosa. METHODS: In the present study, involving 24 healthy subjects, we have examined nasal mucosal drug retention of single doses of topical budesonide (256 microg) and fluticasone propionate (200 microg). Treatments were given consecutively and the administration sequence was randomised. Subjects were randomised into four parallel groups and two nasal biopsies were taken from each subject, i.e. before and at 2 h, at 2 and 6 h, at 6 and 24 h, or before and at 24 h after drug administration, resulting in 12 biopsies/time point. The measurement of unesterified budesonide, budesonide-oleate, budesonide-palmitate, and fluticasone propionate was based on microwave extraction procedures combined with liquid-chromatography/tandem mass-spectrometry. RESULTS: Neither of the analytes was detected in samples taken before glucocorticosteroid administration. After administration, unesterified budesonide, budesonide-esters, and fluticasone propionate were detected in the tissue from 23, 20, and 19 subjects, respectively. The mean tissue levels of budesonide at 2 and 6 h were 1051 and 176 pmol g(-1); the mean levels of fluticasone propionate at these time points were 237 and 10 pmol g(-1). The dose-corrected budesonide/fluticasone propionate tissue concentration ratios were 3.5 (P = 0.07) and 13.7 (P < 0.0002), respectively. At 24 h, budesonide and fluticasone propionate were detected in 8/12 and 3/12 of the biopsies, respectively. CONCLUSIONS: The present study demonstrates the formation of budesonide-esters in the human nasal mucosa in vivo, and that budesonide is retained in the nasal mucosa to a greater extent than fluticasone propionate. It is suggested that the formation of budesonide-esters and their subsequent release of budesonide contributes to an extended retention of budesonide in the airway mucosa.     

脑靶向鼻腔给药的研究进展

目的阐述鼻腔的生理特点和药物由鼻黏膜转运入脑的机制及其影响因素。方法依据近年来的29篇中外文文献,对药物的鼻腔脑靶向实验手段、离体在体模型、鼻黏膜的毒性等方面的研究进展进行阐述。结果鼻黏膜给药途径在脑内递药领域具有独特优势,其在脑部疾病治疗方面具有独到之处,值得进一步深入研究。结论药物的鼻腔脑靶向给药将受到越来越多的关注。     

Development of in situ gel for nasal delivery: design,optimization, in vitro and in vivo evaluation

Abstract

Context: The mucoadhesive gel formulations are helpful to prolong the residence time at the nasal absorption site and thereby facilitate the uptake of drug. Sumatriptan succinate has oral bioavailability of 15% and undergoes hepatic metabolism, hence it is suitable for nasal administration.

Objective: The objective of the investigation was to develop a mucoadhesive in situ gel to improve the bioavailability of the sumatriptan succinate.

Materials and methods: Deacetylated gellan gum was used as gelling agent. In situ gel was formulated by ion activation mechanism in simulated nasal fluid. A 3² factorial design was found suitable to optimize batch. In vivo study was carried out in Spraugue-Dawley rats, and drug was estimated in plasma by UPLC-MS.

Result: The optimized batch showed drug release of 98.57% within 5?h followed by Peppas model of drug release. Ex vivo studies on sheep nasal mucosa showed 93.33% within 5?h. In histopathological study, optimized batch was found to be safe and stable in accelerated stability study for three months. Optimized formulation, F7 has shown absolute bioavailability, which was found to be 164.70%. Drug targeting index for brain tissues was found to be 1.866.

Discussion: Concentration of the gelling polymer was compromised for satisfactory gel strength and an acceptable viscosity. The release depended on viscosity of formulation. Drug targeting index indicates sumatriptan can reach to brain via olfactory pathway.

Conclusion: In situ gel proved to be suitable for administration of sumatriptan succinate through nasal route. The ease of administration coupled with less frequent administration enhances patient compliance.     

Carbopol/chitosan based pH triggered in situ gelling system for ocular delivery of timolol maleate

The poor bioavailability and therapeutic response exhibited by conventional ophthalmic preparations due to rapid precorneal elimination, dilution and nasolacrimal drainage of the drug may be vanquished by the use of in situ gelling systems that are instilled as drops in to the eye and undergo a sol-gel transition in the cul-de-sac. Timolol eye drops may cause systemic side effects in glaucoma patients due to absorption of the drug into systemic circulation. In situ gelling system of this drug can provide localized effect with reduced contraindications, improved patient compliance and better therapeutic index. The present work describes the formulation and evaluation of an ophthalmic delivery system of an antiglaucoma drug, timolol maleate (TM) based on the concept of pH-triggered in situ gelation. Polyacrylic acid (carbopol) was used as the gelling agent in combination with chitosan (amine polysaccharide), which was acted as a viscosity-enhancing agent. Formulations were evaluated for pH, viscosity, gelling capacity and drug content. The 0.4% w/v carbopol/0.5% w/v chitosan based in situ gelling system was in liquid state at room temperature and at the pH formulated (pH 6.0) and underwent rapid transition into the viscous gel phase at the pH of the tear fluid (lacrimal fluid) (pH 7.4). The in vitro drug release and in vivo effects of the developed in situ gelling system were compared with that of Glucomol® (a 0.25% TM ophthalmic solution), 0.4% w/v carbopol solution as well as liposomal formulation. The results clearly demonstrated that developed carbopol-chitosan based formulation was therapeutically efficacious and showed a fickian (diffusion controlled) type of release behaviour over 24 h periods. The developed system is thus a viable alternative to conventional eye drops and can also prevent the rapid drainage as in case of liposomes.     

Development and evaluation of carboplatin-loaded PCL nanoparticles for intranasal delivery

Context: The study was aimed to develop a polymeric nanoparticle formulation of anticancer drug carboplatin using biodegradable polymer polycaprolactone (PCL). The formulation is intended for intranasal administration to treat glioma anticipating improved brain delivery as nasal route possess direct access to brain and nanoparticles have small size to overcome the mucosal and blood–brain barrier.

Objective: Development and evaluation of carboplatin-PCL nanoparticles for brain delivery by nasal route.

Methodology: Carboplatin-loaded PCL nanoparticles (CPCs) were prepared by double emulsion-solvent evaporation technique and characterized by particle size, zeta potential, entrapment efficiency, scanning electron microscopy and differential scanning calorimetry. The CPCs were assessed for in vitro release kinetics, ex vivo permeation and in situ nasal perfusion. Cytotoxic potential of CPCs in vitro was evaluated on LN229 human glioblastoma cells.

Results and discussion: The optimized formulation of carboplatin-PCL nanoparticle CPC-08 with particle size of 311.6?±?4.7?nm and zeta potential ?16.3?±?3.7?mV exhibited percentage entrapment efficiency of 27.95?±?4.21. In vitro drug release showed initial burst release followed by slow and continues release indicating biphasic pattern. The ex vivo permeation pattern through sheep nasal mucosa also exhibited a similar release pattern as for in vitro release studies. In situ nasal perfusion studies in Wistar rats demonstrate that CPCs show better nasal absorption than carboplatin solution. In vitro cytotoxicity studies on LN229 cells showed an enhancement in cytotoxicity by CPCs compared to carboplatin alone.

Conclusion: CPC-08 effectively improves nasal absorption of carboplatin and can be used for intranasal administration of carboplatin for improved brain delivery.     

中药醒鼻温敏凝胶的鼻粘膜毒性考察(英文)

本研究采用生理盐水作为空白对照,含1%盐酸麻黄碱的呋麻滴鼻剂作为阴性对照,显微镜下观察中药醒鼻温敏凝胶对蟾蜍上颚粘膜纤毛运动的影响以及鼻腔给药后,大鼠鼻粘膜组织病理切片变化情况,探讨中药醒鼻温敏凝胶对鼻粘膜纤毛的毒性。结果表明中药醒鼻温敏凝胶对鼻黏膜纤毛运动无影响,与生理盐水的相对运动百分率为94.1%;鼻粘膜组织切片显示无显著病理变化情况。综合我们的实验结果,可以得出中药醒鼻温敏凝胶安全性较高,无明显纤毛毒性,可用于鼻腔给药。     

鼻内镜下鼻中隔黏膜下部分切除术65例分析

目的探讨鼻内镜下鼻中隔黏膜下部分切除术治疗鼻中隔偏曲的临床疗效。方法本组患者65例全部进行鼻内镜下鼻中隔黏膜下部分切除术治疗,术后观察其鼻中隔畸形矫正程度及并发症发生情况。结果本组65例患者鼻中隔偏曲都一次性成功矫正,除切口黏膜外,无其他黏膜破裂。结论鼻内镜下鼻中隔黏膜下部分切除术具有切除范围小,对正常组织损伤小,术后恢复快及并发症少等优点,值得在临床上进一步推广应用。     

三七总皂苷鼻用凝胶喷雾剂的药动学与药效学研究

目的研究自制三七总皂苷鼻用凝胶喷雾剂的生理适应性、家兔给药后体内的药动学过程,及其对心血管疾病的保护作用。方法选用扫描电镜法,考察喷雾剂的鼻纤毛毒性;HPLC法测定三七总皂苷鼻用凝胶喷雾剂家兔鼻腔给药后血样中人参皂苷Rb1、Rg1的浓度,考察药物在体内的动力学过程,并计算药动学参数;建立大鼠急性缺血性心肌梗死模型,考察三七总皂苷鼻用凝胶喷雾剂对心脑血管疾病的保护作用。结果三七总皂苷鼻用凝胶喷雾剂给药后,Rb1、Rg1在家兔体内的过程符合二室模型,其绝对生物利用度比三七总皂苷滴鼻液高,分别为（42．31±7．54）％和（81．06±32．71）％;可大幅减少大鼠左冠状动脉闭塞所致的心肌梗死面积,且呈剂量依赖性,剂量越高,保护作用越强;该喷雾剂基本无明显鼻纤毛毒性。结论药动学、药效学及鼻纤毛毒性试验结果证明,三七总皂苷鼻腔给药制剂具有很好的开发前景。     

In vitro activation of the corticosteroid ciclesonide in animal nasal mucosal homogenates

Ciclesonide, a new corticosteroid for allergic rhinitis, is administered as an inactive parent compound that is converted by esterases to the pharmacologically active metabolite, desisobutyryl-ciclesonide (des-CIC). This study investigated the in vitro activation of ciclesonide in nasal mucosa of multiple animal species. Nasal mucosal homogenates from rats, guinea-pigs, rabbits and dogs were incubated with ciclesonide 0.5 micromol/l (0.271 microg/ml) or 5 micromol/l (2.71 microg/ml) for up to 120 min. Concentrations of ciclesonide and des-CIC were measured by high-performance liquid chromatography with tandem mass spectrometry. Ciclesonide was metabolized to des-CIC in nasal mucosal homogenates of each species. The initial velocities of des-CIC formation ranged from 0.0038 to 0.0150 nmol/min/mg protein and 0.0319 to 0.0983 nmol/min/mg protein in nasal mucosal homogenates incubated with ciclesonide 0.5 micromol/l and 5 micromol/l, respectively. Furthermore, the initial velocities of ciclesonide metabolism ranged from 0.0032 to 0.0142 nmol/min/mg protein and 0.0445 to 0.1316 nmol/min/mg protein in nasal mucosal homogenates incubated with ciclesonide 0.5 micromol/l and 5 micromol/l, respectively. This study confirms that ciclesonide is converted to des-CIC in nasal mucosal homogenates without any marked differences among animal species.     

Proteolysis of Human Calcitonin in Excised Bovine Nasal Mucosa: Elucidation of the Metabolic Pathway by Liquid Secondary lonization Mass Spectrometry (LSIMS) and Matrix Assisted Laser Desorption lonization Mass Spectrometry (MALDI)

Purpose. Two calcitonins, i.e. human calcitonin (hCT) and, for comparison, salmon calcitonin (sCT), were chosen as peptide models to investigate nasal mucosal metabolism. Methods. The susceptibility of hCT and sCT to nasal mucosal enzymes was assessed by in-and-out reflection kinetics experiments in an in vitro model based on the use of freshly excised bovine nasal mucosa, with the mucosal surface of the mucosa facing the peptide solution. The kinetics of CT degradation in the bulk solution was monitored by HPLC. Peptide sequences of the main nasal metabolites of hCT were analyzed by using both liquid secondary ionization mass spectrometry (LSIMS), following HPLC fractionation of the metabolites, and matrix-assisted laser desorption ionization mass (MALDI) spectrometry. For sCT, the molecular weights of two major metabolites were determined by LC-MS with electrospray ionization. Results. Both CTs were readily metabolized by nasal mucosal enzymes. In the concentration range studied metabolic rates were higher with hCT than with sCT. Presence of endopeptidase activities in the nasal mucosa was crucial, cleaving both calcitonins in the central domain of the molecules. Conclusions. Typically, initial metabolic cleavage of hCT in nasal mucosa is due to both chymotryptic- and tryptic-like endopeptidases. The subsequent metabolic break-down follows the sequential pattern of aminopeptidase activity. Tryptic endopeptidase activity is characteristic of nasal sCT cleavage.     

Activation of histamine H3 receptors in human nasal mucosa inhibits sympathetic vasoconstriction

The peripheral histamine H3 receptor is a presynaptic heterologous receptor located on postganglionic sympathetic nerve fibers innervating sympathetic effector systems such as blood vessels and the heart. An extensive body of evidence shows that activation of the histamine H3 receptor attenuates sympathetic tone by presynaptic inhibition of noradrenaline release. It is proposed that this sympathoinhibitory action, in vivo, leads to reduced vasoconstriction, thereby eliciting a vasodilatory effect. In humans, the peripheral histamine H3 receptor has also been shown to exert a sympathoinhibitory function on specific peripheral autonomic effector systems. For example, human saphenous vein and heart possess functional presynaptic histamine H3 receptors on the sympathetic nerve terminals that upon activation decrease the sympathetic tone to these respective organs. The present studies were conducted to define the role of histamine H3 receptors on neurogenic sympathetic vasoconstrictor responses in human nasal turbinate mucosa. Contractility studies were conducted to evaluate the effect of histamine H3 receptor activation on sympathetic vasoconstriction in surgically isolated human nasal turbinate mucosa. We found that the histamine H3 receptor agonist, (R)-alpha-methylhistamine (30 and 300 nM), inhibited electrical field stimulation-induced (neurogenic) sympathetic vasoconstriction in a concentration-dependent fashion. Pretreatment with the selective histamine H3 receptor antagonist, clobenpropit (100 nM), blocked the sympathoinhibitory effect of (R)-alpha-methylhistamine on the neurogenic sympathetic vasoconstriction. In addition, analysis of Taqman mRNA expression studies showed a specific, high level of distribution of the histamine H3 receptor localized in the human nasal mucosa.Taken together, these studies indicate that histamine H3 receptors modulate vascular contractile responses in human nasal mucosa most likely by inhibiting noradrenaline release from sympathetic nerve terminals in nasal mucosa. It is further suggested that histamine H3 receptors may play a role in the regulation of vascular tone and nasal patency in histamine-dependent allergic nasal congestive disease.     

Gene expression and immunochemical localization of major cytochrome P450 drug-metabolizing enzymes in bovine nasal olfactory and respiratory mucosa

Abstract

Despite tremendous advancement in the characterization of nasal enzyme expression, knowledge of the role of the nasal mucosa in the metabolism of xenobiotics is still inadequate, primarily due to the limited availability of in vitro models for nasal metabolism screening studies. An extensive knowledge of the oxidative and conjugative metabolizing capacity of the cattle (Bos taurus) olfactory and respiratory mucosa can aid in efficient use of these tissues for pre-clinical investigations of the biotransformation and toxicity of therapeutic agents following nasal administration or inhalation. Cows are also exposed to a variety of airborne pollutants and pesticides during their lifetime, the metabolism of which can have profound toxicological and ecological consequences. The aim of the present study was to characterize cytochrome P450 (CYP) enzyme expression in the bovine nasal mucosa. Amplification of the specific genes through RT-PCR confirmed expression of several CYP enzymes in bovine hepatic and nasal tissues. The results demonstrate that bovine nasal olfactory and respiratory mucosal and liver tissues express similar populations, families, and distributions of CYP enzymes, as has been previously reported with other species, including humans. Bovine ex vivo tissues can serve as a readily available reference tissue to elucidate preclinical toxico-kinetic effects resulting from exposure to substances in the environment or following drug administration.     

Bioavailability enhancement of ondansetron after nasal administration of Caesalpinia pulcherrima-based microspheres

Abstract

Context: Natural polymers have attracted a great deal of attention for use as potential carriers in site-specific delivery over past decades. Mucoadhesive microspheres are useful tools for nasal drug delivery.

Objectives: To prepare and evaluate mucoadhesive microspheres as mode for nasal delivery of ondansetron using Caesalpinia pulcherrima galactomannan (CPG).

Materials and methods: Conventional spray-dried CPG nasal microspheres loaded with ondansetron for intranasal drug delivery in order to avoid the first pass metabolism with improved therapeutic efficiency in treatment of nausea and vomiting as an alternative therapy to parenterals. Developed microspheres were evaluated for characteristics like particle size, entrapment efficiency, zeta potential, swelling ability, in-vitro mucoadhesion, in-vitro drug release, DSC, XRD study and histopathological evaluation of tissue. CPG-based ondansetron microspheres were studied in rabbits for screening nasal absorption potential of nasal formulation.

Results: Developed nasal microspheres possess entrapment efficiency of 80–89%, higher mucoadhesion of 72–84% across goat nasal mucosa. In-vivo study showed that microspheres based on mucoadhesive polymer were able to promote quick drug absorption as well as enhanced bioavailability of drug.

Discussion: Histopathological studies evaluated biocompatible and nontoxic nature of CPG in nasal cavity. Developed mucoadhesive microspheres by nasal route showed enhancement of bioavailability as compared to oral route in rabbits.

Conclusion: CPG-based mucoadhesive microspheres can successfully deliver ondansetron intranasally, sustain its effect, avoid first pass effect, an alternative route of administration to injection and thus enhance systemic bioavailability of ondansetron hydrochloride.