Raman Chemical Imaging for Ingredient-specific Particle Size Characterization of Aqueous Suspension Nasal Spray Formulations: A Progress Report

Purpose This study was conducted to evaluate the feasibility of using Raman chemical imaging (i.e., Raman imaging microspectroscopy) to establish chemical identity, particle size and particle size distribution (PSD) for a representative corticosteroid in aqueous nasal spray suspension formulations. Materials and Methods The Raman imaging PSD protocol was validated using polystyrene (PS) microsphere size standards (NIST-traceable). A Raman spectral library was developed for the active and inactive compounds in the formulation. Four nasal sprays formulated with beclomethasone dipropionate (BDP) ranging in size from 1.4 to 8.3 μm were imaged by both Raman and brightfield techniques. The Raman images were then processed to calculate the PSD for each formulation. Results Within each region examined, active pharmaceutical ingredient (API) particles are unambiguously identified and the total number of those particles, particle size and PSD of API free of excipients and PSD of API particles adhered to other excipients are reported. Conclusions Good statistical agreement is obtained between the reported and measured sizes of the PS microspheres. BDP particles were clearly distinguishable from those of excipients. Raman chemical imaging (RCI) is able to differentiate between and identify the chemical makeup of multiple components in complex BDP sample and placebo mixtures. The Raman chemical imaging method (coupled Raman and optical imaging) shows promise as a method for characterizing particle size and shape of corticosteroid in aqueous nasal spray suspension formulations. However, rigorous validation of RCI for PSD analysis is incomplete and requires additional research effort. Some specific areas of concern are discussed. This article represents the personal opinions of the authors and does not necessarily represent the views or policies of the US Food and Drug Administration.     

Particle Size and Charge Distribution Analysis of Pharmaceutical Aerosols Generated by Inhalers

Aerosol particles generated by inhalers for respiratory drug delivery acquire electrostatic charge during the dispersion process. The electrostatic charge distribution of the particles can affect the efficiency of drug delivery by influencing both the transport and deposition of inhaled particles in the human lung. To analyze the electrostatic charge acquired by the aerosol particles, two sets of metered-dose inhaler (MDI) and dry powder inhaler (DPI) devices were investigated. Both the particle size and charge distributions were measured simultaneously by using an electrical single-particle aerodynamic relaxation time (E-SPART) analyzer. The analyzer was calibrated with particles of known size, which were generated by a vibrating orifice aerosol generator (TSI Inc.) and charge using the Faraday cup method. The charge distributions of the pharmaceutical aerosols from both the DPI and MDI devices were bipolar in nature. Although the net charge-to-mass ratio was less than 0.2 μC/g, the individual particles were charged with a relatively high charge: ?2 to + 2 μC/g. The count mean aerodynamic diameter of the aerosols generated from these devices was 3–5 μm.     

布地奈德鼻喷雾剂粒度分布的测定及一致性分析

目的:建立布地奈德鼻喷雾剂样品粒度分布的测定方法,并分析其粒度分布的一致性。方法:以水为分散剂,搅拌(1 800 r/min)分散;分别以累积粒度分布为10%、50%、90%所对应的粒径[d(0.1)、d(0.5)、d(0.9)]为特征值。采用光散射法测定样品的粒度分布,并采用SAS 9.3统计软件分析2个厂家(A和B)样品间、同一厂家不同批次间及同一批次内样品粒度分布的一致性。结果:A厂3批样品d(0.1)平均值为3.96μm,d(0.5)平均值为29.58μm,d(0.9)平均值为67.10μm;B厂3批样品d(0.1)平均值为2.00μm,d(0.5)平均值为7.53μm、d(0.9)平均值为28.51μm。通过分析得出,2个厂家样品粒度分布差异较大,A厂样品的粒径大于B厂;B厂样品各批次之间的一致性好于A厂;2个厂家各批次内的一致性均较好。结论:所建立的方法适用于测定布地奈德鼻喷雾剂的粒度分布,并可用于分析其粒度分布的一致性。     

Study of the Hygroscopic Properties of Selected Pharmaceutical Aerosols Using Single Particle Levitation

Purpose. To use a single particle levitation technique to investigate the equilibrium water sorption characteristics in both the evaporation and growth of four respiratory drugs at 37°C: atropine sulfate (AS), isoproterenol hydrochloride (IPHC) and isoproterenol hemisulfate (IPHS) and disodium cromoglycate (DSCG). Methods. The equilibrium water content was measured as a function of relative humidity (RH) by a single particle levitation technique using an electrodynamic balance (EDB). The change of water content was determined by the voltage required to balance the weight of the levitated particle electrostatically. The water activities of bulk samples were also measured. Growth ratios were determined and compared with values in the literature. Results. Crystallization or deliquescence was not observed for AS, IPHC and IPHS. The hysteresis in the water cycle was not observed for any of the drugs. At RH 0%, AS particles still contain about 5% water but IPHC and IPHS particles do not contain any residual water. The aerodynamic growth ratio from RH 0% to 99.5% is 2.60, 2.86, 2.42 and 1.26 for AS, IPHC, IPHS and DSCG, respectively. Super- saturated droplets of IPHC and IPHS are expected to exist in the am- bient conditions. DSCG is in a solid state in the RH range of 10-90%. Conclusions. It is expected that some aerosolized drugs of low solubility may experience supersaturation before they enter the human body and this could exert a significant influence both on particle loss before inhalation and on the deposition of the drugs in the lungs. The EDB is a convenient and reliable tool for studying the hygroscopic properties of pharmaceutical aerosols, especially for supersaturated solutions.     

Assessment of Nasal Spray Deposition Pattern in a Silicone Human Nose Model Using a Color-Based Method

Purpose  

To develop a simple and inexpensive method to visualize and quantify droplet deposition patterns.     

吸入用气雾剂雾粒测定方法的评价

分别采用激光衍射气雾粒径测定（LD）法和飞行时间空气动力学气雾粒径测定（TOF）法测定了以氯氟烃或氢氟烷为抛射剂的沙丁胺醇气雾剂的气雾粒径，并与标准方法（圆盘撞击器法）比较。结果表明，LD法能反映气雾剂气雾发生的过程变化，获得非空气动力学粒径；TOF法获得的为空气动力学粒径参数，与撞击器法测定的结果一致。在控制吸入剂质量研究中可采用快速的LD法和TOF法，而质量控制则以TOF法更为合适。     

Effects of Absorption Enhancers on Human Nasal Tissue Ciliary Movement in Vitro

Sodium taurodihydrofusidate (STDHF) is one of the most promising absorption enhancers for nasal delivery of peptide drugs. Drugs and additives in nasal formulations should not interfere with the self-cleaning capacity of the nose by the ciliary epithelium. Measured in vitro on human adenoid tissue with a photoelectric method, STDHF was found to induce ciliostasis at concentrations of 0.3% (w/v) and higher. STDHF (0.3%) is less ciliostatic than laureth-9 (0.3%) or deoxycholate (0.3%). Glyco- and taurocholate (0.3%) show only very mild effects on nasal ciliary movement. Human insulin (1%) has no ciliostatic potency in vitro, whereas a combination of human insulin (1%) and STDHF (1%) is ciliostatic but not as potent as STDHF (1%) alone.     

Effects of pH and Dose on Nasal Absorption of Scopolamine Hydrobromide in Human Subjects

Purpose. The present study was conducted to evaluate theeffects of formulation pH and dose on nasal absorption of scopolaminehydrobromide, the single most effective drug available for the prevention ofnausea and vomiting induced by motion sickness. Methods. Human subjects received scopolamine nasally at adose of 0.2 mg/0.05 mL or 0.4 mg/0.10 mL, blood samples were collected atdifferent time points, and plasma scopolamine concentrations were determinedby LC-MS/MS. Results. Following administration of a 0.2 mg dose, theaverage C_max values were found to be 262 ± 118, 419± 161, and 488 ± 331 pg/mL for pH 4.0, 7.0, and 9.0formulations, respectively. At the 0.4 mg dose the average C_maxvalues were found to be 503 ± 199, 933 ± 449, and 1,308± 473 pg/mL for pH 4.0, 7.0, and 9.0 formulations, respectively. At a0.2 mg dose, the AUC values were found to be 23,208 ± 6,824, 29,145± 9,225, and 25,721 ± 5,294 pg.min/mL for formulation pH 4.0,7.0, and 9.0, respectively. At a 0.4 mg dose, the average AUC value wasfound to be high for pH 9.0 formulation (70,740 ± 29,381 pg.min/mL)as compared to those of pH 4.0 (59,573 ± 13,700 pg.min/mL) and pH 7.0(55,298 ± 17,305 pg.min/mL) formulations. Both the C_maxand AUC values were almost doubled with doubling the dose. On the otherhand, the average T_max values decreased linearly with a decreasein formulation pH at both doses. For example, at a 0.4 mg dose, the averageT_max values were 26.7 ± 5.8, 15.0 ± 10.0, and 8.8± 2.5 minutes at formulation pH 4.0, 7.0, and 9.0, respectively. Conclusions. Nasal absorption of scopolamine hydrobromidein human subjects increased substantially with increases in formulation pHand dose.     

Influence of Hydrodynamics and Particle Size on the Absorption of Felodipine in Labradors

Purpose. To study the influence of GI hydrodynamics and drug particle size on felodipine absorption in the dog. Methods. Labradors fistulated at midjejunum were used to selectively study the influence of hydrodynamics and particle size on the in vivodissolution and absorption of the poorly soluble, lipophilic drug felodipine. A combination of infusion and oral administration of either normal saline or a 5% glucose solution was used to maintain fasted and establish fed state motility patterns, respectively. The absorption characteristics of both a micronized (8 m) and a coarse fraction (125 m) of felodipine were subsequently studied under these two motility patterns. Results. A reduction in particle size led up to an approximate 22-fold increase in maximum plasma concentration and up to an approximate 14-fold increase in area under the curve, with a commensurate decrease in the time at which the maximum plasma concentration occurred. Although the absorption of felodipine from the solution and micronized suspension was not influenced by a change in the hydrodynamics, felodipine was absorbed from the coarse suspension almost twice as well in the fed state as under fasted conditions. Conclusions. Absorption from coarse suspensions of felodipine was sensitive to luminal hydrodynamics, whereas micronized suspensions were not. However, the particle size seems to have a much more important influence on the bioavailability of felodipine than the hydrodynamics per se.     

A Real-Time Method to Evaluate the Nasal Deposition and Clearance of Acetone in the Human Volunteer

Nasal dosimetry models have become increasingly quantitative as insights into tissue deposition/clearance and computational fluid dynamics have become available. Validation of these models requires sufficient experimental data. However, investigations into respiratory deposition, particularly in human volunteers, have been historically limited due to methodological limitations. To overcome this, a method for evaluating the nasal wash-in, wash-out phenomena of a highly water-soluble compound in human volunteers was developed and characterized. This methodology was assessed using controlled human inhalation exposures to uniformly labeled [13 C]acetone at approximately 1 ppm concentration for 30 min under different breathing maneuvers (inhale nose/exhale nose; inhale nose/exhale mouth; inhale mouth/exhale nose). A small-diameter air-sampling probe inserted in the nasopharyngeal cavity of the volunteer was connected directly to an ion-trap mass spectrometer capable of sampling every 0.8 s. A second ion-trap mass spectrometer simultaneously sampled from the volunteer's exhaled breath stream via a breath-inlet device interface. Together, the two mass spectrometers provided real-time appraisal of the [13 C]acetone concentrations in the nasopharyngeal region and in the exhaled breath stream before, during, and after the different breathing maneuvers. The breathing cycle (depth and frequency) and heart rate were concurrently monitored throughout the exposure using a heart-rate monitor and a human plethysmograph to differentiate inhalation and exhalation. Graphical overlay of the plethysmography results with the mass spectrometer measurements show clear quantifiable differences in [13 C]acetone levels at the nasal probe as a function of breathing maneuvers. Breath-by-breath analyses of [13 C]acetone concentrations indicate that between 40 and 75% of the compound is absorbed upon inhalation and nearly all of that absorbed is released back into the breath stream during exhalation.     

Comparison of Nasal Deposition and Clearance of Aerosol Generated by a Nebulizer and an Aqueous Spray Pump

Pharmaceutical Research -     

Optimized Inhalation Aerosols. I. The Effects of Spherical Baffle Size and Position upon the Output of Several Pressurized Nonaqueous Suspension Formulations

Baffles contained in conventional actuators may be a convenient alternative to some of the extension devices used presently with metered-dose inhalers (MDIs). Actuators were modified to determine whether baffles could be used to decrease the output of large nonrespirable droplets. These actuators were tested using a series of nonaqueous suspension aerosols containing 0.1 to 2.0% micronized disodium fluorescein (DF) as the model drug, stabilized by sorbitan trioleate in a constant blend of fluorocarbons 11, 12, and 114. A 25-µl metering volume was used throughout. Aerosol output was characterized by cascade impaction. Baffle size and position had pronounced effects on actuator retention and aerosol output. Increasing baffle size resulted in increased retention in the actuator. The total output of the MDI in the respirable range (aerodynamic diameter, D _ae, <5.5 µm) was greater in the unbaffled actuator than in all baffled actuators. However, all baffles increased the respirable fraction (DF with D _ae <5.5 µm: total DF leaving the actuator), R, when compared to their unbaffled controls. For example, for a 0.1% DF, 0.14% surfactant formulation, R was increased from 0.40 (unbaffled) to 0.71 by incorporation of a 0.6-cm-diameter sphere 1.3 cm from the jet of the actuator. In these cases, aerosol segregation occurred due to droplet inertia in the high velocity gas flows. Increasing the respirable fraction at the expense of the total respirable output may obviate undesirable clinical effects.     

Effects of Absorption Enhancers on Rat Nasal Epithelium in Vivo: Release of Marker Compounds in the Nasal Cavity

Purpose. The assessment of the effects of nasal absorption enhancers on the rat nasal epithelium and membrane permeability in vivo after a single nasal dose of the enhancers. Methods. The release of marker compounds (protein, cholesterol and acid phosphatase) from the nasal epithelium was measured using a lavage technique. The nasal membrane permeability was determined after intravenous administration of a systemic tracer (FITC-albumin). Results. The effects of the absorption enhancers could be classified into four categories. The first consisted of HPCD (5%), DMCD (2%) and RAMEB (2%) and was not different from the control (physiological saline). For the second category, DMCD (5%), effects were significantly higher than for the control. The third category, SGC (1%), was more active than DMCD (5%) but less active than the last group. The fourth, most membrane damaging, category consisted of STDHF (1%), laureth-9 (1%) and LPC (1%). Administration of these three enhancers also resulted in release of acid phosphatase, indicating that severe membrane damage occurred. The release of cholesterol from nasal epithelium was largely dependent on the cholesterol solubilisation of the absorption enhancers. The amount of cholesterol released by laureth-9 and LPC was the largest. Conclusions. The results of this in vivo study are in agreement (i.e. similarity in rank order) with morphological and ciliotoxicity studies of nasal absorption enhancers, demonstrating that this in vivo model is a valuable tool to classify nasal absorption enhancers according to their effects on the rat nasal epithelium.     

Effects of Pharmaceutical Compounds on Ciliary Beating in Human Nasal Epithelial Cells: A Comparative Study of Cell Culture Models

Purpose. To test two in vitro human nasal epithelial cell culture systems for their ability to screen the effects of pharmaceutical compounds on ciliary beating. Methods. Human nasal epithelial cells were cultured as monolayer and in a sequential monolayer-suspension culture with in vitro ciliogenesis. The influence of reference cilio-stimulatory compounds (glycocholate, isoprenaline), reference cilio-inhibitory compounds (chlorocresol, diphenhydramine) and pH on ciliary beating was investigated using computerized microscope photometry. Results. Sodium glycocholate (0.5% w/v) maximally and reversibly increased CBF of the cells in both culture systems by 26 ± 4% (monolayer) and 18 ± 6% (suspension). Similarly, isoprenaline (10^-3 M) maximally, but irreversibly increased CBF of the cells by 14 ± 3% (monolayer) and 17 ± 4% (suspension). Chlorocresol (0.005% w/ v) reversibly reduced the CBF of the cells by 50 ± 6% (monolayer) and 34 ± 4% (suspension); at a higher concentration (0.1% w/v) it resulted in instantaneous and irreversible ciliostasis. Diphenhydramine (0.1% w/v) reversibly reduced CBF in both culture systems by 45 ± 13% (monolayer) and 69 ± 5% (suspension); irreversible cilio-stasis occurred in less than 2 minutes in both culture systems upon cell exposure to diphenhydramine (1.0% w/v). In the monolayer culture system, CBF was stable only within the physiological pH range of 6.5–8.0; ciliary beating in the suspension culture remained stable within a pH range of 4.0–10.0. Conclusions. Both cell culture systems are suitable for screening the effects of pharmaceutical compounds on ciliary beating. Especially the sequential monolayer-suspension culture appears to be very promising as ciliary activity can be preserved for as long as 6 months.     

Guidance in the Setting of Drug Particle Size Specifications to Minimize Variability in Absorption

Purpose. To provide guidance in setting particle size specifications for poorly soluble drugs to minimize variability in absorption. Methods. A previously reported computer method was used to simulate the percent of dose absorbed as a function of solubility, absorption rate constant, dose, and particle size. Results. The simulated percent of dose absorbed was tabulated over a realistic range of solubilities, absorption rate constants, and doses using drug particle sizes that might be typically found in a dosage form. Conclusions. The greatest effect of particle size on absorption was simulated for low dose- low solubility drugs. In general, the sensitivity of absorption to particle size decreased with increasing dose or solubility. At a solubility of 1 mg/mL, particle size had practically no effect on the percent of dose absorbed over the range of doses simulated (1–250 mg).     

Particle Size Distribution of a Suspension Aerosol Using Andersen and Marple-Miller Cascade Impactors

Pharmaceutical Research -     

Particle Size Distributions of Inert Spheres and Pelletized Pharmaceutical Products by Image Analysis

Image analysis was used to measure particle size distributions (PSDs) of ensembles of 425 to 1400 µm‐size materials. Repeatability of a measurement, suitable sample sizes, and methods of sampling were assessed. Two lots of inert spheres were compared prior to drug layering in a Glatt GPCG‐5 rotor. The differences in PSD in the starting materials were reflected in the rotor‐granulated products. Such detailed information was not available from sieving with U.S. standard wire mesh sieves. The products from the rotor process were polymer‐coated in a Wurster process in a Glatt GPCG‐3, 4‐in. Wurster. The resolution of the technique was sufficient to measure differences in diameter equating to 4‐µm coat thickness, which resulted from applying 2% polymer coat weight. The utility of the technique for monitoring commercial scale processes was demonstrated by measuring diameter after layering drug onto nonpareils in a Glatt RG‐150 rotor, and by measuring the diameter after application of a polymer solution in a Glatt 46‐in. Wurster coating process. The similarity of samples removed from the sample port in situ and samples from the batch suggested that processes in the fluid bed are intensively mixed and inherently random.     

Nasal Absorption in the Rat. III. Effect of Lysophospholipids on Insulin Absorption and Nasal Histology

The intranasal absorption enhancing and histological effects of a range of lysophospholipids has been investigated in the rat. Blood glucose levels fell rapidly following the administration of insulin (8 IU/kg) in combination with lysophosphatidylcholines (LPC; 0.625% w/v) which had ten or more carbon groups in their fatty acid chain. The effect of the LPC-caproyl (C6) was comparable to that of an unenhanced insulin formulation; the enhancing effect of LPC-decanoyl (C10) was similar to that of an LPC-palmitoyl/stearoyl (C16/C18) for similar concentrations. The effect of LPC-decanoyl was reduced with concentration but was still significant at 0.2% w/v (5mM). Lysophosphatidylglycerol (LPG) had a marked insulin absorption enhancing effect even at 0.0625% w/v. The histological effects of LPC-caproyl were similar to those of an unenhanced insulin formulation, while co-administration of LPC-decanoyl resulted in evidence of epithelial interaction. LPG (0.5% w/v) resulted in similar histological changes as LPC (0.625% w/v) (1), but at 0.0625% w/v no significant changes in epithelial integrity were observed. The length of the fatty acid residue of lysophospholipids was identified as an important factor for intranasal absorption enhancing activity. The nature of the polar head group may also have an influence. Increased insulin absorption was not necessarily accompanied by severe disruption of the nasal epithelium. Careful selection of lysophospholipid type and concentration may enable therapeutic drug levels to be achieved via the nasal route without prohibitive toxic effects.     

Influence of Particle Size,Air Flow,and Inhaler Device on the Dispersion of Mannitol Powders as Aerosols

Purpose. To study the effect of particle size, air flow and inhaler type on the dispersion of spray dried mannitol powders into aerosols. Methods. Mannitol powders were prepared by spray drying. The solid state properties of the powders were determined by laser diffraction, X-ray powder diffraction, scanning electron microscopy, freeze fracture, Karl Fischer titration and gas pycnometry. The powders were dispersed using Rotahaler^® and Dinkihaler^®, connected to a multistage liquid impinger at different air flows. Results. Three crystalline mannitol powders with primary particle size (MMD) 2.7, 5.0, 7.3 m and a similar polydispersity were obtained. The particles were spherical with a density of 1.5 g/cm³ and a moisture content of 0.4 wt.%. At an air flow of 30 L/min all the powders were poorly dispersed by both inhalers. With the Rotahaler^® increasing the flow (60–120 L/min) increased the fine particle fraction (FPF) in the aerosols for the 2.7 m powder, and decreased the FPF for the 7.3 m powder; whereas the FPF for 5.0 m powder was unaffected. With the Dinkihaler^®, all the powders were near complete dispersion at 60 L/min. Conclusions. The FPF in the mannitol powder aerosols was determined by an interplay of the particle size, air flow and inhaler design.