Effect of carrier particle shape on dry powder inhaler performance

The aim of this study was to characterise the aerosolisation properties of salbutamol sulphate (SS) from dry powder inhaler (DPI) formulations containing different carrier products. The difference in the elongation ratio (ER) of the different carriers was highlighted. Different set of carriers, namely commercial mannitol (CM), commercial lactose (CL), cooling crystallised mannitol (CCM), acetone crystallised mannitol (ACM) and ethanol crystallised mannitol (ECM) were used and inspected in terms of size, shape, density, crystal form, flowability, and in vitro aerosolisation performance using Multi Stage Liquid Impinger (MSLI) and Aerolizer^® inhaler device. Solid-state and morphological characterization showed that CM product was in pure β-form having particles with smaller ER (CM: ER = 1.62 ± 0.04) whereas ACM and ECM mannitol particles were in pure α form with higher ER (ACM: ER = 4.83 ± 0.18, ECM: ER = 5.89 ± 0.19). CCM product crystallised as mixtures of β-form and δ-form and showed the largest variability in terms of particle shape, size, and DPI performance. Linear relationships were established showing that carrier products with higher ER have smaller bulk density (D_b), smaller tap density (D_t), higher porosity (P), and poorer flow properties. In vitro aerosolisation assessments showed that the higher the ER of the carrier particles the greater the amounts of SS delivered to lower airway regions indicating enhanced DPI performance. Yet, DPI performance enhancement by increasing carrier ER reached a “limit” as increasing carrier ER from 4.83 ± 0.18 (ACM) to 5.89 ± 0.19 (ECM) did not significantly alter fine particle fraction (FPF) of SS. Also, carrier particles with higher ER were disadvantageous in terms of higher amounts of SS remained in inhaler device (drug loss) and deposited on throat. Linear relationship was established (r² = 0.87) showing that the higher the carrier ER the lower the drug emission (EM) upon inhalation. Moreover, poorer flowability for carrier products with higher ER is disadvantageous in terms of DPI formulation dose metering and processing on handling scale. In conclusion, despite that using carrier particles with higher ER can considerably increase the amounts of drug delivered to lower airway regions; this enhancement is restricted to certain point. Also, other limitations should be taken into account including higher drug loss and poorer flowability.     

Characterisation and functionality of inhalation anhydrous lactose

The relationships between the physicochemical properties and functionality in dry powder inhaler (DPI) performance was investigated for inhalation grade anhydrous lactose and compared to monohydrate grades. The excipients were characterised using a range of techniques including particle size analysis, moisture sorption and powder rheometry. The inhalation anhydrous lactose grades were readily characterisable. The aerosolisation performance of capsule based DPI formulations containing budesonide (200 μg) and different grades of lactose evaluated using inertial impaction measurements produced fine particle doses of budesonide ranging from 24 to 49 μg. There were no apparent relationships between aerosolisation performance and excipient characteristics, such as particle size and powder density. However, formulations containing lactose grades which exhibit higher powder fluidisation energy values resulted in higher fine particle doses of budesonide.     

The kinetics of cohesive powder de-agglomeration from three inhaler devices

Purpose

The purpose of the current investigation is to understand the kinetics of de-agglomeration (k_d) of micronised salbutamol sulphate (SS) and lactohale 300 (LH300) under varying air flow rates (30-180 l min⁻¹) from three dry powder inhaler devices (DPIs), Rotahaler^® (RH), Monodose Inhaler^® (MI) and Handihaler^® (HH).

Results

Cumulative fine particle mass vs. time profiles were obtained from the powder concentration, emitted mass and volume percent <5.4 μm, embedded in the particle size distributions of the aerosol at specific times. The rate of de-agglomeration (k_d), estimated from non-linear least squares modelling, increased with increasing air flow rates. The k_dvs. air flow rate profiles of SS and LH300 were significantly different at high air flow rates. The k_d was highest from RH and lowest from MI. Differences in k_d between the devices were related to device mode of operation while the differences between the materials were due to the powder bed structure.

Conclusion

This approach provided a methodology to measure the rate constant for cohesive powder de-agglomeration following aerosolisation from commercial devices and an initial understanding of the influence of device, air flow rate and material on these rate constants.     

Structural influence of cohesive mixtures of salbutamol sulphate and lactose on aerosolisation and de-agglomeration behaviour under dynamic conditions

PurposeThe purpose of this study was to understand the behaviour of cohesive powder mixtures of salbutamol sulphate (SS) and micronized lactose (LH300) at ratios of SS:LH300 of 1:1, 1:2, 1:4 and 1:8 under varying air flow conditions.MethodsAerosolisation of particles less than 5.4 μm at air flow rates from 30 to 180 l min^?1 was investigated by determining particle size distributions of the aerosolised particles using laser diffraction and fine particle fractions of SS using the twin stage impinger modified for different air flow rates using a Rotahaler^®. The de-agglomeration data were best fitted by a 3-parameter sigmoidal equation using non-linear least squares regression and characterised by the estimated parameters.ResultsDe-agglomeration air flow rate profiles showed that SS:LH300 mixtures with increased lactose content (1:4 and 1:8) improved powder aerosolisation, but lactose had negligible effect on SS aerosolisation at the higher and lower limits of air flow rates studied. De-agglomeration flow rate profiles of SS–LH300 mixtures with increased lactose content (1:4 and 1:8) were greater than theoretically expected based on weighted individual SS and LH300 profiles. This indicated that interactions between the cohesive components led to enhanced de-agglomeration. The composition of the aerosol plume changed with air flow rate.ConclusionThis approach to characterising aerosolisation behaviour has significant applications in understanding powder structures and in formulation design for optimal aerosolisation properties.     

Engineered Mannitol Ternary Additives Improve Dispersion of Lactose–Salbutamol Sulphate Dry Powder Inhalations

The aim of this study was to evaluate the influence of novel engineered fine mannitol particles (4.7%, w/w) on the performance of lactose–salbutamol sulphate dry powder inhaler (DPI) formulations to obtain promising aerosolisation properties. The results showed that the more elongated the fine mannitol particles, the weaker the drug–carrier adhesion, the better the drug content homogeneity, the higher the amount of drug expected to be delivered to the lower airways and the higher the total DPI formulation desirability. Linear relationships were established showing that mannitol particles with a more elongated shape generated powders with broader size distributions and that were less uniform in shape. The weaker the drug–carrier adhesion, the higher the fine particle fraction of the drug is upon aerosolisation. It is believed that more elongated fine mannitol particles reduce the number of drug–carrier and drug–drug physical contact points and increase the ability of the drug particles to travel into the lower airways. Additionally, a lower drug–carrier contact area, lower drug–carrier press-on forces and easier drug–carrier detachment are suggested in the case of formulations containing more elongated fine mannitol particles. Ternary ‘drug-coarse carrier-elongated fine ternary component’ DPI formulations were more favourable than both ‘drug-coarse carrier’ and ‘drug-elongated coarse carrier’ binary formulations. This study provides a comprehensive approach for formulators to overcome the undesirable properties of dry powder inhalers, as both improved aerosolisation performance and reasonable flow characteristics were obtained using only a small amount of elongated engineered fine mannitol particles.     

The effect of polymer properties on direct compression and drug release from water-insoluble controlled release matrix tablets

The objective of this study was to identify and evaluate key polymer properties affecting direct compression and drug release from water-insoluble matrices. Commonly used polymers, such as Kollidon^® SR, Eudragit^® RS and ethyl cellulose, were characterized, formulated into tablets and compared with regard to their properties in dry and wet state. A similar site percolation threshold of 65% v/v was found for all polymers in dry state. Key parameters influencing polymer compactibility were the surface properties and the glass transition temperature (T_g), affecting polymer elasticity and particle size-dependent binding. The important properties observed in dry state also governed matrix characteristics and therefore drug release in wet state. A low T_g (Kollidon^® SR < Eudragit^® RS) decreased the percolation threshold, particle size effect and tortuosity, but increased permeability and sensitivity to heat/humidity treatment. Hence, lower permeability and higher stability are benefits of a high-T_g polymer (ethyl cellulose). However, release retardation was observed in the same order as matrix integrity (Eudragit^® RS < ethyl cellulose < Kollidon^® SR), as the high permeability was counteracted by PVP in case of Kollidon^® SR. Therefore, the T_g and composition of a polymer need to be considered in polymer design and formulation of controlled-release matrix systems.     

Formulation of thermoresponsive and bioadhesive gel for treatment of oesophageal pain and inflammation

The aim of this study was the formulation and examination of a novel thermoresponsive and bioadhesive, in situ gelling drug delivery system, which can be used in the treatment of oesophageal pain and inflammation. A bioadhesive cellulose derivative (Metolose^® 60SH) was used as a thermoresponsive material, because Metolose^® has thermal gelation properties at certain temperature. The thermal gelation temperature (T₂) of Metolose^® 60SH 2 w/w% solution is above body temperature (65-66 °C), but by using different methods (Metolose^® 60SH concentration, auxiliary materials), it can be shifted near to body temperature. The pH alteration between pH = 2-10 and the application of different alcohols did not influence the gelation temperature, but using water-soluble salts and changing the concentration of Metolose^® 60SH solution between 2 and 3 w/w% the thermal gelation point could be decreased. Different NSAIDs were used as model drugs and which had not influence on thermal gelation temperature, but difference in in vitro liberation and penetration can be observed. In vitro adhesion test pointed out that the condition of investigated membrane can change the adhesion. Morphological test of oesophageal tissue showed that investigated materials had no irritative or tissue-damaging effect on the oesophageal mucosa even after 12 h.     

Influence of crystal form of ipratropium bromide on micronisation and aerosolisation behaviour in dry powder inhaler formulations

Objectives This study aimed to investigate the relationship between the mechanical properties of anhydrous and monohydrate ipratropium bromide (IB) crystals, their processing behaviour upon air‐jet micronisation and aerosolisation performance in dry powder inhaler (DPI) formulations. Methods IB monohydrate and anhydrous crystals were produced from seed crystals and supercritical carbon dioxide crystallisation, respectively. Young's modulus of anhydrous and monohydrate IB crystals was determined using nanoindentation. For air‐jet micronised crystals, the physicochemical and surface interfacial properties via the cohesive–adhesive balance (CAB) approach were investigated. These data were correlated to in‐vitro aerosolisation performance of carrier‐based DPI formulations containing either anhydrous or monohydrate IB. Key findings Particle size and Young's modulus of both crystals were similar and this was reflected in their similar processing upon micronisation. Particle size of micronised anhydrous and monohydrate crystals were similar. CAB measurements of the micronised particles of monohydrate or anhydrous forms of IB with respect to lactose were 0.70 (R² = 0.998) and 0.77 (R² = 0.999), respectively. These data suggested that both samples had similar adhesion to lactose, which correlated with their similar in‐vitro aerosolisation performance in DPI formulations. Conclusions Monohydrate and anhydrous crystals of IB exhibited similar mechanical properties and interfacial properties upon secondary processing. As a result, the performance of the DPI formulations were similar.     

An approach to a cold chain free oral cholera vaccine: in vitro and in vivo characterization of Vibrio cholerae gastro-resistant microparticles

The present work describes the formulation of Eudragit^® L30 D-55 microparticles (MP) alone or with mucoadhesive agents, alginate or Carbopol^®, as an approach for the development of an oral cholera vaccine. In the first part, a spray drying technique was optimized for microparticle elaboration, obtaining a microparticle size ranging from 7 to 9 μm with high encapsulation efficiencies. Moreover, gastro resistant properties and Vibrio cholerae (VC) antigenicity were maintained, but for Eudragit^®-Carbopol^® microparticles which showed low antigenicity values, ≈25%. Next, a stability study was performed following ICH Q1 A (R2) guidelines, i.e. 25 °C-60% relative humidity (RH) for 12 months, and 30 °C-65% RH and 40 °C-75% RH for 6 months. Upon storage, microparticle size changed slightly, 1 μm for Eudragit^®-alginate MPs and 0.36 μm for Eudragit^®MP. However, gastro resistance and antigenicity values were kept in an acceptance range. In the third stage of this work, in vivo experiments were performed. The immune response evoked was measured by means of vibriocidal titer quantification, observing that Eudragit^®-alginate MPs were able to induce stronger immune responses, comparable to the free VC. Therefore, microencapsulation of VC by spray drying could be proposed as an approach to a cold chain free and effective oral cholera vaccine.     

Effects of particle size and adding sequence of fine lactose on the deposition of salbutamol sulphate from a dry powder formulation.

Ternary mixtures composed of coarse lactose (CL) (90.8 microm), salbutamol sulphate (SS) (5.8 microm) and either micronised lactose (ML) (5 microm) or intermediate sized lactose (IML) (15.9 microm) in a ratio of 66.5:1:1 w/w were prepared using different mixing sequences of the various components. In addition, a binary mixture composed of CL and SS (67.5:1 w/w) was also prepared as the control. The in vitro deposition of SS was measured using a twin stage impinger after aerosolisation at 60 and 90 l min-1 via a Rotahaler. The aerodynamic particle size distribution of both the aerosolised SS and lactose was further analysed using an Andersen cascade impactor at 60 l min-1. All ternary mixtures produced a significantly higher (analysis of variance, P<0.01) fine particle fraction (FPF) and fine particle dose (FPD) of SS than the control after aerosolisation at either 60 or 90 l min-1. Formulations containing the ML produced significantly (P<0.05) higher FPF and FPD of SS than those containing the IML at both aerosolisation flow rates. Different mixing sequences were also shown to result in different deposition profiles of both SS and lactose after aerosolisation of the ternary mixtures containing ML at 60 l min-1. The formulation prepared by first blending ML with CL before mixing with SS produced a higher FPF and FPD of SS but a lower FPF of lactose than the same formulation in terms of composition but prepared using different mixing orders of the three components. In contrast, the formulations containing IML produced a similar deposition profile to SS, regardless of the mixing sequences, and so did the formulations containing ML aerosolised at 90 l min-1. These results suggest that the effect of mixing sequences on drug deposition may become more prominent at lower aerosolisation flow rates and by reducing the size of any added fine lactose.     

Thermal ink-jet spray freeze-drying for preparation of excipient-free salbutamol sulphate for inhalation

The use of thermal ink-jet spray freeze-drying (TIJ-SFD) to engineer inhalable, excipient-free salbutamol sulphate (SS) particles was assessed. A modified Hewlett-Packard printer was used to atomise aqueous SS solutions into liquid nitrogen. The frozen droplets were freeze-dried. It was found that TIJ-SFD could process SS solutions up to 15% w/v; the porous particles produced had a physical diameter of ca. 35 μm. Next generation impactor (NGI) analysis indicated that the particles had a smaller aerodynamic size (MMAD ranging from 6 to 8.7 μm). Particles prepared from the lowest concentration SS solution were too fragile to withstand aerosolisation, but the 5% w/v solution yielded particles having the best combination of strength and aerodynamic properties. Comparison with a commercial SS formulation (Cyclocap®) showed that the SFD preparation had an almost equivalent FPF_6.4μm when analysed with a twin-stage impinger (TSI; 24.0 ± 1.2% and 26.4 ± 2.2%, respectively) and good performance when analysed with NGI (FPF_4.46μm:16.5 ± 2.0 and 27.7 ± 1.7, respectively). TIJ-SFD appears to be an excellent method to prepare inhalable particles. It is scalable yet allows assessment of the viability of the pulmonary route early in the development since it can be used with very small volumes (<0.5 mL) of solution.     

Determination of cidofovir in human plasma after low dose drug administration using high-performance liquid chromatography–tandem mass spectrometry

A sensitive and specific method for the determination of cidofovir (CDV) in human plasma using high-performance liquid chromatography with tandem mass spectrometry (LC–MS/MS) was developed and validated. Plasma samples were processed by a solid phase extraction (SPE) procedure using Varian^® SAX extraction cartridges prior to chromatography. The internal standard was ¹³C5-Folic acid (¹³C5-FA). Chromatography was performed using a Luna C8(2) analytical column, 5 μm, 150 mm × 3.0 mm, using an isocratic elution with a mobile phase consisting of 43% methanol in water containing 12 mM ammonium acetate, at a flow rate of 0.3 mL/min. The retention times of CDV and ¹³C5-FA were 2.1 min and 1.9 min, respectively, with a total run time of 5 min. The analytes were detected by a Micromass Quattro Micro triple quadrupole mass spectrometer in positive electron spray ionization (ESI) mode using multiple reaction monitoring (MRM). The extracted ions monitored following MRM transitions were m/z 280.0 → 262.1 for CDV and m/z 447.0 → 294.8 for ¹³C5-FA (IS). The assay was linear over the range 20–1000 ng/mL. Accuracy (101.6–105.7%), intra-assay precision (4.1–5.4%), and inter-assay precision (5.6–6.8%) were within FDA limits. No significant variation in the concentration of CDV was observed with different sample storage conditions. This method is simple, adaptable to routine application, and allows easy and accurate measurement of CDV in human plasma.     

Development and validation of a stability-indicating HPLC method for simultaneous determination of salicylic acid,betamethasone dipropionate and their related compounds in Diprosalic Lotion

Diprosalic Lotion^® is an anti-inflammatory drug product that contains salicylic acid and betamethasone dipropionate as active pharmaceutical ingredients (APIs). A reversed-phase high performance liquid chromatography (RP-HPLC) method was developed for simultaneous determination of salicylic acid, betamethasone dipropionate, and their related compounds in Diprosalic Lotion^®. A 150 mm × 4.6 mm I.D. YMC J'sphere ODS-H80 column at 35 °C and UV detection at 240 nm was used. A gradient elution was employed using 0.05% (v/v) methanesulfonic acid solution and acetonitrile as mobile phases. A total of thirty three compounds from Diprosalic Lotion^® samples were separated in 38 min. The stability-indicating capability of this method has been demonstrated by the adequate separation of all the impurities and degradation products in expired stability samples of Diprosalic Lotion^®. The method was validated as per the current ICH guidelines.     

Effect of three anthelmentics on disposition kinetics of florfenicol in goats

The pharmacokinetic aspects of florfenicol (FLO) were investigated via intravenous (I.V.) and intramuscular (I.M.) injections in five goats at a dose of 20 mg kg⁻¹ b.wt. Animals were pre-treated with albendazole orally in a dose of 2.5 mg kg⁻¹ b.wt, ivermectin or rafoxanide subcutaneously in a dose 0.2 and 7.5 mg kg⁻¹ b.wt, respectively. Florfenicol was injected intramuscularly two hours following anthelmentic administration and blood samples were taken by jugular venapuncture at standardized intervals. The concentrations of florfenicol (FLO) in serum were determined by high performance liquid chromatography (HPLC) method. The obtained results revealed that ivermectin administration did not induce a significant difference in serum florfenicol concentration between anthelmentic-treated and non-treated goats. On the other hand, goats pre-treated with rafoxanide or albendazole showed a significant decrease in serum florfenicol level as compared to non-anthementic treated goats. The absorption half-life (t_½ab), C_max, AUMC, AUC and systemic bioavailability (F%) are significantly decreased, whereas elimination half-life (t_½el) and MRT are increased in goats pre-treated by the three tested anthementics.     

Improved aerosolization performance of salbutamol sulfate formulated with lactose crystallized from binary mixtures of ethanol-acetone

It has been shown that dry powder inhaler (DPI) formulations typically achieve low fine particle fractions (poor performance). A commonly held theory is that this is due, at least in part, to low levels of detachment of drug from lactose during aerosolization as a result of strong adhesion of drug particles to the carrier surfaces. Therefore, the purpose of the present study is to overcome poor aerosolization performance of DPI formulation by modification of lactose particles. Lactose particles were crystallized by adding solution in water to different ratios of binary mixtures of ethanol-acetone. The results showed that modified lactose particles had exceptional aerosolization performance that makes them superior to commercial lactose particles. Morphology assessment showed that crystallized lactose particles were less elongated, more irregular in shape, and composed of smaller primary lactose particles compared with commercial lactose. Solid-state characterization showed that commercial lactose particles were α-lactose monohydrate, whereas crystallized lactose particles were a mixture of α-lactose monohydrate and β-lactose according to the ratio of ethanol-acetone used during crystallization process. The enhanced performance could be mainly due to rougher surface and/or higher amounts of fines compared with the lactose crystallized from pure ethanol or commercial lactose.     

Literature review on the safety of Toyocerin,a non-toxigenic and non-pathogenic Bacillus cereus var. toyoi preparation

Bacillus cereus var. toyoi is a naturally occurring, non-toxigenic and non-pathogenic strain of B. cereus. Safety studies were conducted on a B. toyoi preparation (Toyocerin^®), including but not limited to enterotoxicity, eye irritation, genotoxicity, acute, subchronic and chronic toxicity studies and human clinical trials. In rabbits, Toyocerin^® did not exhibit enterotoxicity and was only slightly irritating to the eyes. It was non-mutagenic in an Ames assay at up to 10,000 μg/plate and did not exhibit clastogenic activity in a chromosomal aberration test at up to 450 mg/ml. It was non-toxic in acute and repeated-dose (30 and 60 days and 1 year) toxicity studies in rats and mice at up to 3 × 10¹¹ spores/kg bw/day. In an eight-day human clinical trial, Toyocerin^® did not cause any adverse effects in healthy male and female subjects at 1 × 10⁹ and 1 × 10¹⁰ spores/kg bw/day. In feeding trials, Toyocerin^® did not cause any adverse effects in rabbits, pigs, chickens, turkeys and cattle at doses ranging from 8.5 × 10⁷ to 4 × 10⁹ spores/kg bw/day for durations of 2 weeks to 18 months. Taken together, these studies demonstrate that Toyocerin^® is safe at the doses tested.     

Note on the formulation of thermosensitive and mucoadhesive vaginal hydrogels containing the miniCD4 M48U1 as anti-HIV-1 microbicide

The miniCD4 M48U1 was formulated into thermosensitive and mucoadhesive pluronic^® hydrogels as anti-HIV-1 microbicide. The release kinetics of M48U1 from F127/HPMC (20/1 wt%) and F127/F68/HPMC (22.5/2.5/1 wt%) studied during 24 h by using Franz diffusion cells showed that HEC hydrogel (1.5 wt%) used as control released 93% of the peptide, while about 25% of M48U1 remained in pluronic^® hydrogels. The formulation of M48U1 in pluronic^® hydrogels ensures a local delivery because no diffusion of the peptide was detected through vaginal Cynomolgus macaque mucosa using Ussing chamber. Finally, toxicological studies showed no significant difference in the HeLa cell viability of the pluronic^® hydrogels in comparison with HEC and phosphate buffer saline.     

Beneficial effects of citrulline malate on skeletal muscle function in endotoxemic rat

Although citrulline malate (CM; CAS 54940-97-5, Stimol^®) is used against fatigue states, its anti-asthenic effect remains poorly documented. The objective of this double-blind study was to evaluate the effect of oral ingestion of CM on a rat model of asthenia, using in situ ³¹Phosphorus magnetic resonance spectroscopy (³¹P-MRS). Muscle weakness was induced by intraperitoneal injections of Klebsiella pneumoniae endotoxin (lipopolysaccharides at 3 mg/kg) at t₀ and t₀ + 24 h. For each animal, muscle function was investigated strictly non-invasively before (t₀ − 24 h) and during (t₀ + 48 h) endotoxemia, through a standardized rest-stimulation-recovery protocol. The transcutaneous electrical stimulation protocol consisted of 5.7 min of repeated isometric contractions at a frequency of 3.3 Hz, and force production was measured with an ergometer. CM supplementation in endotoxemic animals prevented the basal phosphocreatine/ATP ratio reduction and normalized the intracellular pH (pH_i) time-course during muscular activity as a sign of an effect at the muscle energetics level. In addition, CM treatment avoided the endotoxemia-induced decline in developed force. These results demonstrate the efficiency of CM for limiting skeletal muscle dysfunction in rats treated with bacterial endotoxin.